The epidemiology and medical management of low back pain during ambulatory medical care visits in the United States

1750-4732-2-11 1750-4732 Research The epidemiology and medical management of low back pain during ambulatory medical care visits in the United States Licciardone C John licciar@hsc.unt.edu

The Osteopathic Research Center, University of North Texas Health Science Center, Fort Worth, TX, USA

Osteopathic Medicine and Primary Care 1750-4732 2008 2 1 11 http://www.om-pc.com/content/2/1/11 19025636 10.1186/1750-4732-2-11 10 8 2008 24 11 2008 24 11 2008 2008 Licciardone; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background

Low back pain (LBP) is a common symptom.

Methods

Patient visits attributed to LBP in the National Ambulatory Medical Care Survey (NAMCS) during 2003–2004 served as the basis for epidemiological analyses (n = 1539). The subset of patient visits in which LBP was the primary reason for seeking care (primary LBP patient visits) served as the basis for medical management analyses (n = 1042). National population estimates were derived using statistical weighting techniques.

Results

There were 61.7 million (SE, 4.0 million) LBP patient visits and 42.4 million (SE, 3.1 million) primary LBP patient visits. Only 55% of LBP patient visits were provided by primary care physicians. Age, geographic region, chronicity of symptoms, injury, type of physician provider, and physician specialty were associated with LBP patient visits. Age, injury, primary care physician status, type of physician provider, and shared physician care were associated with chronicity of LBP care. Osteopathic physicians were more likely than allopathic physicians to provide medical care during LBP patient visits (odds ratio [OR], 2.61; 95% confidence interval [CI], 1.75–3.92) and chronic LBP patient visits (OR, 4.39; 95% CI, 2.47–7.80). Nonsteroidal anti-inflammatory drugs (NSAIDs) and narcotic analgesics were ordered during 14.2 million (SE, 1.2 million) and 10.5 million (SE, 1.1 million) primary LBP patient visits, respectively. Drugs (OR, 0.29; 95% CI, 0.13–0.62) and, specifically, NSAIDs (OR, 0.40; 95% CI, 0.25–0.64) were ordered less often during chronic LBP patient visits compared with acute LBP patient visits. Overall, osteopathic physicians were less likely than allopathic physicians to order NSAIDs for LBP (OR, 0.43; 95% CI, 0.24–0.76). Almost two million surgical procedures were ordered, scheduled, or performed during primary LBP patient visits.

Conclusion

The percentage of LBP visits provided by primary care physicians in the United States remains suboptimal. Medical management of LBP, particularly chronic LBP, appears to over-utilize surgery relative to more conservative measures such as patient counseling, non-narcotic analgesics, and other drug therapies. Osteopathic physicians are more likely to provide LBP care, and less likely to use NSAIDs during such visits, than their allopathic counterparts. In general, LBP medical management does not appear to be in accord with evidence-based guidelines.

Background

Back pain is a common symptom in industrialized nations that is responsible for substantial morbidity, impairment, and disability. Low back problems have been leading reasons for patient visits and health care costs despite measures to control access to services and contain costs 1. Health care costs and productivity losses, most often associated with chronicity 2, may be in excess of $50 billion annually in the United States 3.

Back problems almost always consist of or co-exist with pain, including back-related leg pain or sciatica 4. Although generically referred to as "back problems"4 or "back pain," most cases involve the lower back. Low back pain (LBP) is defined as pain localized between the twelfth rib and the inferior gluteal folds, with or without leg pain 5. Low back pain is often classified as acute when it lasts for less than 6 weeks, subacute when it lasts between 6 weeks and 3 months, and chronic when it persists for longer than 3 months 6. The vast majority of LBP cases involve a non-specific etiology. Yellow flags (including individual, psychosocial, and occupational factors 7) are prognostic factors for occurrence and chronicity of such non-specific LBP, whereas red flags are signs or symptoms that have come to be associated with specific pathological causes of LBP 5.

Historically, LBP has taken up a large part of primary care practice 8. It has been the second leading cause of office visits to primary care physicians 9, and the most common reason for office visits to occupational medicine physicians, orthopedic surgeons, and neurosurgeons 4. Allopathic family (general) medicine physicians, osteopathic physicians, chiropractors, orthopedic surgeons, and other specialists are the main providers of LBP care in the United States 10. A variety of treatments for LBP have been introduced into clinical practice, including educational interventions, exercise, weight reduction, various classes of analgesics, nonsteroidal anti-inflammatory drugs, muscle relaxants, antidepressants, behavioral therapy, physical therapy, spinal manipulation, other complementary and alternative therapies, and surgery 1112.

The purpose of this study was to elucidate the epidemiology and medical management of LBP during ambulatory medical care visits in the United States.

Methods

Overview of the National Ambulatory Medical Care Survey design

The concept of the National Ambulatory Medical Care Survey (NAMCS) to collect data on medical care provided in physician offices in the United States was developed over 30 years ago 13. Detailed documentation of the NAMCS instrument, methodology, and data files that served as the basis for this study is available elsewhere 1415. Patient visits were selected using a multistage probability sample design. The first stage included primary sampling units (PSUs) which consisted of counties, groups of counties, county equivalents (e.g. parishes), towns, townships, minor civil divisions, or metropolitan statistical areas (MSAs). These PSUs comprised a probability subsample of those used in the 1985–1994 National Health Interview Surveys 16. The latter, which covered all 50 states and the District of Columbia, were stratified by demographic and socioeconomic variables and then selected with probability proportional to their size. Stratification was done within four geographic regions by MSA and non-MSA status.

The second stage consisted of a probability sample of practicing physicians selected from the master files of the American Medical Association (AMA) and American Osteopathic Association (AOA). Within each PSU, all eligible physicians were further stratified by specialty. The third stage involved selection of patient visits within the practices of participating physicians. Initially, physicians were randomly assigned to one of the 52 weeks within a calendar year. Then, a systematic random sample of patient visits was selected for each physician during the assigned week. The sampling rate of patient visits varied from a 20% sample for very large practices to 100% for very small practices as determined by a presurvey interview 17. In this manner, data from about 30 patient visits were recorded by each physician during the assigned week.

Sampling frame and sample size

The sampling frame for NAMCS included physicians who met the criteria of being: (1) office-based; (2) principally engaged in patient care activities; (3) nonfederally employed; and (4) not in the specialties of anesthesiology, pathology, or radiology. During 2003 and 2004, a total of 6000 physicians were initially screened. Of these, 2032 (34%) did not meet the four inclusion criteria, most commonly because the physician was retired, deceased, or employed in teaching, research, or administration. Of the remaining 3968 eligible physicians, 2779 (70%) participated in NAMCS. However, among these "participating" physicians, 544 (20%) saw no patients during their assigned reporting period because of vacations, illness, or other reasons for being temporarily not in practice. The NAMCS provides data on 25,288 patient visits to 1114 physician offices during the 2003 calendar year and 25,286 patient visits to 1121 physician offices during the 2004 calendar year.

Patient visits and weights

The basic sampling unit for the NAMCS is the physician-patient encounter or "patient visit." The following types of contacts were excluded: telephone calls, visits outside the physician's office (e.g., house calls), visits made in hospital settings (unless the physician had a private office in a hospital), visits made in institutional settings that had primary responsibility for the patient's care (e.g., nursing homes), and visits to the physician's office for administrative purposes only (e.g., to leave a specimen, pay a bill, or pick up insurance forms). Each patient visit was assigned a weight based on four factors: (1) probability of being selected by the three-stage sampling design; (2) adjustment for nonresponse; (3) adjustment for physician specialty group; and (4) weight smoothing to minimize the impact of a few physician outliers whose final visit weights were large relative to those for the remaining physicians. Thus, by applying these weights to each of the 50,574 patient visits in the 2003 and 2004 NAMCS data files, an estimated 1.8 billion physician office visits in the United States were available to derive unbiased national estimates of ambulatory medical care services and to further characterize such services.

Data collection and processing

Data for the NAMCS were collected by the physician with assistance from office staff when possible. Patient record forms were used to collect the data for each selected visit. The NAMCS field staff performed completeness checks of the patient record forms prior to submission for central data processing. Detailed editing instructions were provided to reclassify or recode ambiguous or inconsistent data entries. Quality control measures, which were used to verify the accuracy of computer data entry, indicated that the mean keying error rate was 0.1% for nonmedical items and that discrepancy rates ranged from 0.0% to 1.1% for required medical items.

Item nonresponse rates were 5% or less for most variables. Major exceptions (nonresponse rate) included: ethnicity (20%), race (18%), tobacco use (30%), and time spent with physician (16%). Missing data for birth year (4%), sex (4%), race (18%), ethnicity (20%), and time spent with physician (16%) were imputed by assigning the value from a randomly selected patient record form representing another patient with similar known characteristics. Such imputations were performed according to physician specialty, geographic region (state was used instead of geographic region to impute ethnicity), and primary diagnosis codes.

Data management and statistical analyses

This study focused on patient visits for LBP. These were initially identified using the "reason for visit" (RFV) item of the NAMCS patient record form. Specifically, patient visits were included only if back symptoms (RFV classification code number, 1905) or low back symptoms (RFV classification code number, 1910) were reported as one of the three most important reasons for the visit in the patient's own words. Subsequently, any patient visits attributed to a lump, mass, or tumor of the back or low back were excluded. Exploratory analyses of the data stratified according to RFV classification code numbers (1905 vs. 1910) and importance of symptoms (primary reason for visit vs. secondary or tertiary reason for visit) revealed few substantive differences between groups. Consequently, to maximize statistical power, all epidemiological analyses combined RFV classification code numbers 1905 and 1910 to represent prevalent cases of LBP (i.e., back symptoms, other than those attributed to a lump, mass, or tumor, were the primary, secondary, or tertiary reason for the patient visit). However, only those patient visits in which LBP was the primary reason for seeking medical care ("primary LBP patient visits") were included in the medical management analyses to minimize potential confounding by other secondary or tertiary reasons for the patient visit. Patient visits attributed to neck symptoms (RFV classification code number, 1900) exclusive of LBP were not included in the study. National population estimates derived from the NAMCS may be unreliable if they are based on fewer than 30 unweighted patient visits or if the relative standard error (standard error divided by the national population estimate) is greater than 0.30 1415.

Patient sociodemographic characteristics included age, sex, race, ethnicity, geographic region, and MSA status of residence. Patient visit context characteristics included episode of care, chronicity of symptoms, and whether the visit was related to an injury, poisoning, or adverse effect (IPA). Physician provider characteristics included primary care physician status, type of physician provider (Doctor of Medicine or Doctor of Osteopathy), physician specialty, and whether multiple physicians shared responsibility for medical care of the patient. The elements of LBP medical management included any diagnostic tests, patient counseling, drugs, physiotherapy, or surgical procedures that were ordered, scheduled, or performed during the patient visit. Drugs were broadly defined as any medications or injections, including immunizations, allergy shots, anesthetics, or dietary supplements, that were ordered, supplied, administered, or continued during the visit, regardless of prescription or over-the-counter status. Up to eight drugs may have been listed on the NAMCS patient record form during a patient visit. For each drug listed, up to three therapeutic class codes were assigned based on the standard classifications used in the National Drug Code (NDC) Directory 18. The drugs portion of this study focused exclusively on three common drugs for relief of pain (NDC code, 1700): (1) non-narcotic analgesics (NDC code, 1722); (2) narcotic analgesics (NDC code, 1721); and (3) nonsteroidal anti-inflammatory drugs (NSAIDs) (NDC code, 1727), including antiarthritics (NDC code, 1724). To maintain consistency with the NDC codes used in the NAMCS patient record form, the term "narcotic analgesic" will be used herein rather than "opioid." Physiotherapy consisted of treatments using heat, light, sound, physical pressure, or movement, including manipulative therapy.

To study the epidemiology of LBP, national population estimates of patient visits were derived and stratified according to patient sociodemographic, patient visit context, and physician provider characteristics. Multiple logistic regression was used to compute adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for factors associated with LBP patient visits compared with patient visits for all other reasons. Similar analyses were repeated according to chronicity of LBP: (1) initial visits for acute LBP and (2) follow-up visits for chronic LBP. To study the LBP medical management, national population estimates of the use of diagnostic tests, patient counseling, drugs, physiotherapy, and surgical procedures were derived for patient visits in which LBP was the primary reason for seeking medical care. Simple logistic regression was initially performed to compute crude ORs and 95% CIs for the elements of chronic LBP medical management compared with acute LBP medical management. Multiple logistic regression was subsequently used to compute adjusted ORs and 95% CIs for the most commonly used elements of LBP medical management. All hypotheses were tested at the .05 level of statistical significance.

The electronic files containing the 2003 and 2004 NAMCS data were acquired from the National Center for Health Statistics. The files were merged and analyzed using SPSS Version 14.0 for Windows (SPSS Inc., Chicago, IL). Because the multistage probability design of the NAMCS includes clustering, stratification, and the assignment of unequal probabilities of selection to sample units, all analyses were performed with the SPSS complex samples module to accurately compute estimates of population parameters and their standard errors 19. A check of these statistical procedures, which involved the entire 2003 and 2004 NAMCS databases, verified that the computed marginal totals for national population estimates were identical to those published by the National Center for Health Statistics 1415.

Results

National population estimates of patient visits for low back pain

There were an estimated 31 million (3%) patient visits annually attributed to LBP in the United States. For the 2003–2004 period, 1539 patient record forms representing 61.7 million (SE, 4.0 million) LBP patient visits and 1042 patient record forms representing 42.4 million (SE, 3.1 million) primary LBP patient visits were included in the analyses reported herein (Figure 1). The physician specialties most commonly seen during LBP patient visits were family (general) medicine, 25.2 million (SE, 2.3 million); internal medicine, 14.4 million (SE, 3.0 million); and orthopedics, 5.6 million (SE, 0.9 million). In orthopedics, one of every 16 patient visits involved LBP (one of every 11 working-age patients seen for reasons other than preventive or surgery-related care). In family (general) medicine, one of every 17 patient visits involved LBP (one of every 13 working-age patients seen for reasons other than preventive or surgery-related care). Patient visits for LBP were attributed to the following factors: (1) back pain, ache, soreness, or discomfort, 94%; (2) other back symptoms, including cramps, contractures, spasms, limitation of movement or stiffness, or weakness, 2%; and (3) other unspecified back symptoms, 4%. Prior to combining LBP patient visits, they were originally designated as RFV classification code number 1905 in 39.0 million (SE, 2.7 million) patient visits and as RFV classification code number 1910 in 22.8 million (SE, 2.0 million) patient visits. A total of 42.4 million (SE, 3.1 million) patient visits (69%) involved LBP as the primary reason for seeking medical care.

Figure 1

National population estimates of patient visits for low back pain in the United States, 2003–2004

National population estimates of patient visits for low back pain in the United States, 2003–2004. LBP indicates low back pain; NPE, national population estimate; SE, standard error. National population estimates are for both years combined and were computed by applying patient visits weights to the numbers reported in the National Ambulatory Medical Care Survey. Patient visits involving back symptoms attributed to a lump, mass, or tumor are not included as LBP visits. Patient visits other than initial visits for acute problems or follow-up visits for chronic problems are not represented under the "all LBP visits" and "primary LBP visits" headings.

There were few differences in patient visit characteristics according to the importance of LBP (primary reason for seeking medical care vs. secondary or tertiary reasons for seeking medical care) or RFV classification code number (1905 vs. 1910) (Table 1). Neurologists were less likely than other physician specialties to provide care for primary LBP (P = .05). Hispanics were more likely than non-Hispanics (P = .02) and osteopathic physicians were more likely than allopathic physicians (P = .04) to involve RFV classification code number 1910 rather than 1905.

Table 1

Patient Visits for Low Back Pain According to Importance and Classification of Reason for Visit, 2003–2004 (N = 1,539)*

Importance of Reason for Visit

Reason for Visit Classification Code†

Primary

Secondary or Tertiary

1905

1910

Characteristic

NPE

Patient age, y

<25

2,828

420

1,595

316

3,257

430

1,167

274

25–44

340

14,052

1,194

133

5,308

553

289

11,598

1,091

184

7,763

666

45–64

392

16,122

1,796

206

7,476

934

364

14,192

1,279

234

9,406

1,432

≥ 65

237

9,424

1,118

126

4,910

620

249

9,918

1,209

114

4,417

655

Patient sex

Female

589

24,275

1,941

319

12,377

875

582

23,178

1,852

326

13,474

1,074

Male

453

18,152

1,716

188

6,913

749

401

15,786

1,312

240

9,279

1,277

Patient race

White

936

37,791

2,951

439

16,567

1,140

870

33,905

2,480

505

20,453

1,815

Non-White

106

4,635

637

2,724

604

113

5,059

924

2,300

366

Patient ethnicity

Non-Hispanic

943

38,746

3,055

458

17,455

1,155

903

36,011

2,604

498

20,189

1,821

Hispanic

3,681

509

1,836

378

2,953

484

2,563

395

Geographic region

Northeast

292

13,189

2,211

149

5,376

760

253

10,157

1,582

188

8,408

1,689

Midwest

222

8,102

1,146

107

3,602

400

216

7,966

1,170

113

3,739

447

South

313

11,984

1,319

146

5,964

607

315

12,592

1,411

144

5,356

558

West

215

9,152

1,313

105

4,348

580

199

8,249

1,090

121

5,250

683

MSA status

MSA

861

36,579

3,208

432

17,125

1,344

815

33,342

2,882

478

20,362

2,034

Non-MSA

181

5,848

1,653

2,166

599

168

5,623

1,497

2,391

652

Episode of care

Initial

351

14,286

1,126

158

6,210

614

322

13,279

1,093

187

7,217

743

Follow-up

617

24,754

2,483

304

10,893

1,011

586

22,309

1,962

335

13,338

1,699

Other or missing

3,387

545

2,188

373

3,376

543

2,198

371

Chronicity of symptoms

Acute

402

16,819

1,260

169

6,632

685

360

14,820

1,292

211

8,631

712

Chronic, routine

398

16,797

2,342

211

7,096

845

380

14,874

1,685

229

9,019

1,603

Chronic, flare-up

176

6,494

779

2,990

404

171

6,280

724

3,203

513

Other or missing‡

2,317

402

2,573

471

2,990

388

1,900

340

IPA etiology

722

28,796

2,161

341

13,215

1,006

698

27,443

2,195

365

14,568

1,201

Yes

320

13,631

1,449

166

6,075

716

285

11,522

1,040

201

8,185

1,100

PCP status

Non-PCP or unknown

589

18,744

2,306

314

9,241

918

532

16,465

1,940

371

11,519

1,564

PCP

453

23,683

1,845

193

10,049

958

451

22,499

1,823

195

11,233

934

Type of physician

Doctor of Medicine

782

31,845

2,192

407

15,399

1,080

762

30,832

2,257

427

16,412

1,132

Doctor of Osteopathy

260

10,582

2,130

100

3,892

600

221

8,132

1,434

139

6,341

1,631

Physician specialty

Family (general) medicine

404

18,523

1,737

145

6,687

692

382

17,484

1,879

167

7,725

1,011

Internal medicine

107

9,702

2,264

4,703

1,008

8,199

1,257

6,206§

2,234

Neurology

141

1,244

218

1,011

213

132

1,138

181

105

1,116

322

Orthopedics

151

3,618

546

2,020

489

121

3,025

478

2,613

505

All other specialties

239

9,340

1,278

146

4,869

586

252

9,118

1,160

133

5,092

697

Shared physician care

No or unknown

715

31,694

2,633

336

13,417

1,007

690

28,951

2,184

361

16,160

1,692

Yes

327

10,733

1,017

171

5,873

672

293

10,013

963

205

6,593

703

Total

1,042

42,427

3,108

100

507

19,290

1,201

100

983

38,964

2,655

100

566

22,753

1,957

100

Abbreviations: IPA, injury, poisoning, or adverse effect of medical treatment; MSA, metropolitan statistical area; NPE, national population estimate for the two-year interval; PCP, primary care physician, SE, standard error of the national population estimate.

*Table entries for NPE and SE are in thousands; percentages are based on NPE.

†1905 represents back pain and 1910 represents low back pain.

‡Other options included pre- or post-surgery visits, prenatal care, and health maintenance visits.

§NPE may be unreliable because SE>30% of NPE.

The epidemiology of ambulatory medical care visits for low back pain

Patient visits for LBP predominantly involved persons aged 25 to 64 years (69%) and females (59%) (Table 2). A majority of patient visits were for follow-up care. Patient visits were about evenly divided between acute and routine chronic LBP, and about one-third of visits were attributed to an IPA. Among the estimated 8.4 million patient visits in which an IPA was specified, 7.4 million (88%) involved injuries (primarily overuse syndromes, motor vehicle accidents, or falls) and 0.9 million (11%) involved adverse effects of surgical procedures, drugs, or environmental agents. Thus, IPAs served as a useful surrogate for injuries. Only slightly more than half (55%) of the patient visits were provided by primary care physicians.

Table 2

Patient Visits According to Presence or Absence of Low Back Pain, 2003–2004 (N = 50,558)*

LBP Status

LBP Present

LBP Absent

LBP Visits

Primary LBP Visits†

Characteristic

NPE

OR‡

95% CI

OR‡

95% CI

Patient age, y

<25

115

4,423

572

10,764

431,753

24,165

0.30

0.22 0.41

0.26

0.18 – 0.38

25–44

473

19,360

1,410

10,212

378,110

19,956

1.00

...

1.00

...

45–64

598

23,599

2,409

14,426

497,737

25,996

0.84

0.71 – 1.00

0.78

0.65 – 0.95

≥ 65

363

14,335

1,443

13,607

447,079

23,110

0.60

0.47 – 0.75

0.54

0.41 – 0.70

Patient sex

Female

908

36,652

2,539

27,581

1,035,915

46,027

1.00

...

1.00

...

Male

641

25,065

2,042

21,428

718,765

32,578

0.93

0.81 – 1.06

1.01

0.85 – 1.20

Patient race

White

1,375

54,358

3,825

42,716

1,497,330

71,034

1.00

...

1.00

...

Non-White

174

7,359

1,015

6,293

257,349

16,925

0.88

0.68 – 1.14

0.80

0.61 – 1.06

Patient ethnicity

Non-Hispanic

1,401

56,201

3,846

44,432

1,565,163

68,318

1.00

...

1.00

...

Hispanic

148

5,516

676

4,577

189,516

22,488

1.02

0.81 – 1.29

1.01

0.76 – 1.34

Geographic region

Northeast

441

18,566

2,856

10,111

340,535

31,296

1.00

...

1.00

...

Midwest

329

11,704

1,608

11,056

367,864

38,458

0.56

0.40 – 0.77

0.53

0.37 – 0.75

South

459

17,948

1,584

17,262

674,752

49,514

0.56

0.40 – 0.77

0.52

0.36 – 0.75

West

320

13,499

1,630

10,580

371,528

29,742

0.75

0.52 – 1.07

0.71

0.48 – 1.06

MSA status

MSA

1,293

53,704

4,318

42,768

1,534,434

99,888

1.00

...

1.00

...

Non-MSA

256

8,013

2,093

6,241

220,245

51,084

1.00

0.78 – 1.28

1.06

0.79 – 1.43

Episode of care

Initial

509

20,495

1,431

14,004

526,779

23,102

1.00

...

1.00

...

Follow-up

921

35,647

3,256

26,324

829,669

41,893

0.98

0.83 – 1.16

1.02

0.83 – 1.26

Other or missing

119

5,575

706

8,681

398,231

23,040

0.80

0.56 – 1.14

0.88

0.57 – 1.36

Chronicity of symptoms

Acute

571

23,451

1,602

15,741

615,627

25,898

1.00

...

1.00

...

Chronic, routine

609

23,893

2,932

17,885

561,484

30,854

1.37

1.08 – 1.74

1.36

1.03 – 1.79

Chronic, flare-up

255

9,483

985

4,493

139,324

9,200

2.09

1.65 – 2.65

2.03

1.58 – 2.63

Other or missing§

114

4,890

618

10,890

438,244

24,905

0.52

0.35 – 0.77

0.33

0.20 – 0.56

IPA etiology

1,063

42,011

2,824

43,823

1,569,266

68,357

1.00

...

1.00

...

Yes

486

19,707

1,785

5,186

185,413

10,269

3.38

2.75 – 4.14

3.33

2.64 – 4.21

PCP status

Non-PCP or unknown

903

27,985

2,959

33,809

925,652

54,734

1.00

...

1.00

...

PCP

646

33,732

2,345

15,200

829,027

38,795

0.84

0.61 – 1.16

0.82

0.55 – 1.21

Type of physician

Doctor of Medicine

1,189

47,244

2,859

45,316

1,636,480

72,120

1.00

...

1.00

...

Doctor of Osteopathy

360

14,474

2,718

3,693

118,199

12,647

2.61

1.75 – 3.92

2.68

1.77 – 4.06

Physician specialty

Family (general) medicine

549

25,210

2,259

8,240

405,563

26,625

3.28

2.26 – 4.77

3.59

2.26 – 5.72

Internal medicine

161

14,405

3,074

3,044

273,218

23,834

3.34

2.11 – 5.27

3.38

1.95 – 5.85

Neurology

237

2,255

405

3,202

25,403

2,685

3.97

2.69 – 5.85

3.25

2.07 – 5.08

Orthopedics

217

5,638

896

2,521

82,010

9,469

2.27

1.48 – 3.49

2.19

1.35 – 3.53

All other specialties

385

14,209

1,688

32,002

968,485

49,844

1.00

...

1.00

...

Shared physician care

No or unknown

1,051

45,111

3,282

35,679

1,339,868

60,278

1.00

...

1.00

...

Yes

498

16,606

1,413

13,330

414,812

22,483

1.17

0.99 – 1.39

1.09

0.88 – 1.35

Total

1,549

61,717

3,988

100

49,009

1,754,679

76,123

100

...

Abbreviations: CI, confidence interval; IPA, injury, poisoning, or adverse effect of medical treatment; LBP, low back pain; MSA, metropolitan statistical area; NPE, national population estimate for the two-year interval; OR, odds ratio; PCP, primary care physician, SE, standard error of the national population estimate.

*Table entries for NPE and SE are in thousands; percentages are based on NPE.

†Includes only patient visits in which LBP was the primary reason for seeking medical care (n = 1042).

‡Adjusted for all variables shown.

§Other options included pre- or post-surgery visits, prenatal care, and health maintenance visits.

When compared with the 1.8 billion (SE, 7.6 million) patient visits for reasons other than back symptoms, LBP visits were associated with several factors (Table 2). Low back pain was less likely the reason for a patient visit in all younger and older age categories compared with the referent category (25–44 years) (P < .001). There was a geographic variation in patient visits attributed to LBP (P = .001), with fewer visits in the Midwest and South than in the Northeast. Patient visits for LBP were more likely to reflect chronicity of symptoms, either routine ongoing problems or flare-ups, than were patient visits for other reasons (P < .001). However, injuries, as reflected by the surrogate IPA item, were important predictors of LBP patient visits (P < .001). The type of physician provider (P < .001) and physician specialty (P < .001) were associated with LBP patient visits, with osteopathic physicians, family (general) medicine physicians, internal medicine physicians, neurologists, and orthopedic surgeons being more likely to provide medical care during such visits. Similar findings were observed when the analyses involved only primary LBP patient visits rather than all LBP patient visits.

A total of 15.8 million (SE, 1.0 million) LBP patient visits were initial visits for an acute problem (less than three months since onset) and 27.4 million (SE, 2.8 million) LBP patient visits were follow-up visits for chronic LBP (Table 3). Age <25 years (P < .001), injury (P < .001), and being seen by a primary care physician (P = .01) were inversely associated with LBP chronicity, whereas being seen by an osteopathic physician (P < .001) and shared physician care (P = .003) were directly associated with LBP chronicity. Again, similar findings were observed when the analyses involved only primary LBP patient visits rather than all LBP patient visits.

Table 3

Patient Visits for Low Back Pain According to Chronicity, 2003–2004 (n = 1,062)*

Chronicity

Acute Problem

(Initial Visit)

Chronic Problem

(Follow-Up Visit)

Chronic Problem Visits

Primary Chronic Problem Visits†

Characteristic

NPE

OR‡

95% CI

OR‡

95% CI

Patient age, y

<25

2,012

287

836§

197

0.27

0.13-0.55

0.20

0.09-0.45

25–44

112

5,351

565

195

7,920

907

1.00

...

1.00

...

45–64

123

5,157

597

287

11,025

1,867

1.27

0.84-1.93

1.24

0.81-1.91

≥ 65

3,237

542

190

7,585

1,110

1.42

0.84-2.40

1.29

0.66-2.50

Patient sex

Female

218

9,242

757

400

15,815

1,684

1.00

...

1.00

...

Male

146

6,515

775

298

11,551

1,463

1.17

0.79-1.73

1.22

0.81-1.85

Patient race

White

329

13,955

966

619

24,498

2,821

1.00

...

1.00

...

Non-White

1,802

404

2,867

554

1.03

0.60-1.76

0.85

0.45-1.60

Patient ethnicity

Non-Hispanic

326

14,164

984

642

25,299

2,718

1.00

...

1.00

...

Hispanic

1,593

334

2,066

386

0.74

0.42-1.32

0.86

0.41-1.77

Geographic region

Northeast

3,494

363

211

9,671

2,386

1.00

...

1.00

...

Midwest

3,189

495

133

3,918

452

0.65

0.40-1.08

0.66

0.33-1.32

South

131

5,775

670

201

7,569

848

0.86

0.52-1.40

0.90

0.51-1.61

West

3,299

460

153

6,207

1,214

1.23

0.62-2.46

1.03

0.45-2.38

MSA status

MSA

307

13,706

1,113

588

24,113

2,917

1.00

...

1.00

...

Non-MSA

2,050

572

110

3,252

973

1.16

0.67-1.99

1.05

0.58-1.92

IPA etiology

224

9,611

860

518

20,345

1,874

1.00

...

1.00

...

Yes

140

6,146

586

180

7,020

1,350

0.46

0.31-0.67

0.49

0.32-0.75

PCP status

Non-PCP or unknown

170

4,733

518

437

13,841

2,151

1.00

...

1.00

...

PCP

194

11,024

963

261

13,524

1,366

0.45

0.26-0.79

0.48

0.25-0.90

Type of physician

Doctor of Medicine

299

13,656

932

497

18,256

1,623

1.00

...

1.00

Doctor of Osteopathy

2,101

285

201

9,109

2,402

4.39

2.47-7.80

4.08

2.26-7.36

Physician specialty

Family (general) medicine

163

7,990

768

227

10,248

1,341

0.58

0.31-1.07

0.64

0.31-1.32

Internal medicine

3,611

560

7162§

2,603

0.97

0.48-1.95

0.98

0.40-2.39

Neurology

287

129

1,283

262

1.41

0.67-2.94

0.91

0.34-2.45

Orthopedics

1,064

166

2,279

407

0.89

0.48-1.65

1.17

0.50-2.73

All other specialties

2,804

372

181

6,394

1,096

1.00

...

1.00

...

Shared physician care

No or unknown

283

13,096

1,008

448

19,240

2,565

1.00

...

1.00

...

Yes

2,661

401

250

8,125

960

2.11

1.30-3.44

2.15

1.18-3.93

Total

364

15,757

1,018

100

698

27,365

2,844

100

...

Abbreviations: CI, confidence interval; IPA, injury, poisoning, or adverse effect of medical treatment; MSA, metropolitan statistical area; NPE, national population estimate for the two-year interval; OR, odds ratio; PCP, primary care physician, SE, standard error of the national population estimate.

*Table entries for NPE and SE are in thousands; percentages are based on NPE.

†Includes only patient visits in which low back pain was the primary reason for seeking medical care (n = 710).

‡Adjusted for all variables shown.

§NPE may be unreliable because n<30 or SE>30% of NPE.

The medical management of primary low back pain during ambulatory medical care visits

Overall, a majority of primary LBP patient visits included diagnostic tests (89%), patient counseling (53%), and orders for drugs (72%) (Figures 2, 3, 4, respectively). Compared with patient visits in which LBP was absent, primary LBP patient visits were more likely to involve patient counseling (OR, 1.54; 95% CI, 1.17–2.04) and physiotherapy (OR, 7.89; 95% CI, 6.01–10.35); however, they were less likely to involve surgical procedures (OR, 0.56; 95% CI, 0.38–0.83). There were no significant differences in the frequency of diagnostic tests performed or drugs ordered. The most common elements of LBP medical management included radiographs (13%), exercise counseling (20%), NSAIDs (34%), narcotic analgesics (25%), and physiotherapy (20%). There were 14.2 million (SE, 1.2 million) and 10.5 million (SE, 1.1 million) orders, respectively, for NSAIDs and narcotic analgesics during these primary LBP patient visits (Table 4). Except for the variables "exercise counseling," "any patient counseling," "narcotic analgesics," "NSAIDs," and "any drug ordered," the elements of primary LBP medical management were not reported in sufficiently high numbers of patient visits to provide statistically valid and reliable comparisons of initial visits for acute LBP and follow-up visits for chronic LBP. Drugs generally (P = .002), and NSAIDs specifically (P < .001), were ordered less often during follow-up visits for chronic LBP than during initial visits for acute LBP. Similarly, diagnostic tests were generally performed less often during follow-up visits for chronic LBP than during initial visits for acute LBP (P = .003). However, surgical procedures were ordered more often during follow-up visits for chronic LBP than during initial visits for acute LBP (P < .001).

Figure 2

Diagnostic tests in the medical management of primary low back pain in the United States, 2003–2004

Diagnostic tests in the medical management of primary low back pain in the United States, 2003–2004. Other imaging tests are exclusive of mammograms.

Figure 3

Patient counseling in the medical management of primary low back pain in the United States, 2003–2004

Patient counseling in the medical management of primary low back pain in the United States, 2003–2004. Mental health counseling also includes stress management and psychotherapy.

Figure 4

Drugs ordered in the medical management of primary low back pain in the United States, 2003–2004

Drugs ordered in the medical management of primary low back pain in the United States, 2003–2004. NSAID indicates nonsteroidal anti-inflammatory drug.

Table 4

Medical Management during Patient Visits in which Low Back Pain was the Primary Reason for Seeking Care, 2003–2004 (n = 1,042)*

Chronicity

LBP Visits

Acute Problem

(Initial Visit)

Chronic Problem

(Follow-Up Visit)

Chronic Problem Visits

Medical Management

NPE

95% CI

Diagnostic tests

Complete blood count

2,663

416

525

197

1,165

265

1.32

0.52-3.37

Urinalysis

3,243

456

1,754

359

613

161

0.18

0.09-0.37

Radiograph

142

5,602

634

2,385

406

830

195

0.17

0.09-0.32

Other imaging test†

2,434

345

632

146

904

191

0.83

0.44-1.58

Any diagnostic test

926

37,683

2,608

244

10,807

809

396

15,734

1,419

0.14

0.04-0.49

Patient counseling

Diet or nutrition

3,335

602

734

196

1,688

488

1.38

0.58-3.32

Weight reduction

2,232

529

504

183

1,143

384

1.35

0.52-3.49

Exercise

204

8,320

1,070

2,196

391

3,979

771

1.08

0.63-1.85

Mental health counseling‡

1,859

639

240

124

1,176

525

3.00

0.94-9.61

Any patient counseling

513

22,397

2,510

119

5,408

563

224

10,138

1,956

1.21

0.70-2.11

Drugs

Non-narcotic analgesics

2,492

431

669

201

1,351

301

1.20

0.51-2.82

Narcotic analgesics

261

10,503

1,128

2,385

444

141

5,355

758

1.44

0.76-2.72

NSAIDs (including antiarthritics)

333

14,237

1,180

113

5,497

596

128

5,288

667

0.40

0.25-0.64

Any drug

729

30,523

2,012

204

9,746

798

316

12,703

1,233

0.29

0.13-0.62

Physiotherapy§

179

8,596

2,135

1,408

325

4,866

1,887

2.38

0.93-6.07

Surgical procedure

1,932

407

1,042

304

12.62

3.18-50.07

Total

1,042

42,427

3,108

100

253

11,111

798

100

457

18,948

2,154

100

...

Abbreviations: CI, confidence interval; LBP, low back pain; NPE, national population estimate for the two-year interval; NSAID, nonsteroidal anti-inflammatory drug; OR, odds ratio; SE, standard error of the national population estimate.

*Table entries for NPE and SE are in thousands; percentages are based on NPE. NPEs may not be reliable for variables other than any diagnostic test, any patient counseling, any drug, exercise counseling, NSAIDs, and narcotic analgesics because n<30 and/or SE>30% of NPE.

†Excluding mammograms.

‡Including mental health counseling, stress management, or psychotherapy.

§Including spinal manipulation.

Several other factors emerged in association with the common elements of primary LBP medical management after controlling for potential confounders (Table 5). Patient counseling was less often provided for non-Whites (P = .04) and in geographic regions outside the Northeast (P = .01), although it was provided more often when injuries were reported (P < .001). Specifically, with regard to exercise counseling, there remained a geographic variation (P = .003) and propensity for use following injury (P < .001). However, exercise counseling was less often provided in non-MSAs (P = .04) and by various physician specialties (P < .001), including family (general) medicine physicians and internal medicine physicians.

Table 5

Factors Associated with Medical Management during Patient Visits in which Low Back Pain was the Primary Reason for Seeking Care, 2003–2004 (n = 710)*

Medical Management

Exercise Counseling

Any Patient Counseling

Narcotic Analgesic

NSAID

Any Drug

Characteristic

OR†

95% CI

OR†

95% CI

OR†

95% CI

OR†

95% CI

OR†

95% CI

Patient age, y

<25

0.53

0.15 – 1.90

0.64

0.27 – 1.53

0.35

0.11 – 1.11

0.93

0.44·1.94

0.19

0.08 – 0.50

25–44

1.00

...

1.00

...

1.00

...

1.00

...

1.00

...

45–64

1.20

0.66 – 2.19

1.08

0.66 – 1.75

0.80

0.47 – 1.36

0.64

0.39·1.06

0.63

0.36 – 1.09

≥65

0.93

0.47 – 1.83

0.67

0.38 – 1.19

0.42

0.21 – 0.84

0.73

0.44·1.20

0.77

0.38 – 1.56

Patient sex

Female

1.00

...

1.00

...

1.00

...

1.00

...

1.00

...

Male

0.85

0.52 – 1.38

0.91

0.62 – 1.36

0.90

0.59 – 1.39

0.99

0.68·1.45

0.76

0.50 – 1.14

Patient race

White

1.00

...

1.00

...

1.00

...

1.00

...

1.00

...

Non-White

0.66

0.23 – 1.89

0.49

0.25 – 0.96

0.91

0.42 – 2.01

1.30

0.60·2.84

3.54

1.40 – 8.97

Patient ethnicity

Non-Hispanic

1.00

...

1.00

...

1.00

...

1.00

...

1.00

...

Hispanic

1.45

0.77 – 2.77

1.45

0.77 – 2.77

0.30

0.11 – 0.76

1.12

0.53·2.36

1.78

0.73 – 4.36

Geographic region

Northeast

1.00

...

1.00

...

1.00

...

1.00

...

1.00

...

Midwest

0.33

0.14 – 0.78

0.29

0.14 – 0.60

1.18

0.43 – 3.24

2.05

0.93 – 4.49

2.00

0.67 – 5.97

South

0.27

0.13 – 0.56

0.36

0.17 – 0.74

1.16

0.50 – 2.72

1.81

0.84 – 3.90

2.23

0.98 – 5.08

West

0.59

0.26 – 1.34

0.45

0.22 – 0.93

1.56

0.63 – 3.84

1.45

0.67 – 3.14

1.85

0.75 – 4.56

MSA status

MSA

1.00

...

1.00

...

1.00

...

1.00

...

1.00

...

Non-MSA

0.45

0.21 – 0.96

0.77

0.38 – 1.53

1.96

1.06 – 3.63

0.90

0.40 – 2.07

2.90

0.64 – 13.08

Chronicity

Acute (initial visit)

1.00

...

1.00

...

1.00

...

1.00

...

1.00

...

Chronic (follow-up visit)

0.87

0.48 – 1.59

1.16

0.72 – 1.87

1.54

0.87 – 2.75

0.56

0.37 – 0.86

0.35

0.19 – 0.64

IPA etiology

1.00

...

1.00

...

1.00

...

1.00

...

1.00

...

Yes

2.34

1.49 – 3.68

2.38

1.50 – 3.77

0.74

0.44 – 1.27

1.19

0.83 – 1.73

0.62

0.36 – 1.08

PCP status

Non-PCP or unknown

1.00

...

1.00

...

1.00

...

1.00

...

1.00

...

PCP

1.59

0.67 – 3.76

1.10

0.56 – 2.17

1.38

0.72 – 2.67

1.62

1.05 – 2.49

1.98

1.19 – 3.28

Type of physician

Doctor of Medicine

1.00

...

1.00

...

1.00

...

1.00

...

1.00

...

Doctor of Osteopathy

1.53

0.80 – 2.92

1.02

0.46 – 2.26

0.70

0.31 – 1.58

0.43

0.24 – 0.76

0.44

0.18 – 1.11

Physician specialty

Family (general) medicine

0.30

0.12 – 0.74

0.71

0.32 – 1.59

0.99

0.46 – 2.12

1.52

0.79 – 2.92

2.38

1.06 – 5.35

Internal medicine

0.15

0.05 – 0.40

0.42

0.13 – 1.32

0.63

0.25 – 1.62

0.68

0.28 – 1.69

0.73

0.28 – 1.87

Neurology

0.24

0.06 – 0.94

0.50

0.18 – 1.39

0.88

0.38 – 2.05

0.94

0.43 – 2.04

0.86

0.38 – 1.98

Orthopedics

1.55

0.59 – 4.05

1.01

0.40 – 2.55

0.81

0.33 – 2.00

0.97

0.39 – 2.40

0.45

0.16 – 1.31

All other specialties

1.00

...

1.00

...

1.00

...

1.00

...

1.00

...

Shared physician care

No or unknown

1.00

...

1.00

...

1.00

...

1.00

...

1.00

...

Yes

1.13

0.62 – 2.08

1.08

0.62 – 1.87

1.61

0.95 – 2.76

1.28

0.70 – 2.36

1.02

0.60 – 1.75

Abbreviations: CI, confidence interval; IPA, injury, poisoning, or adverse effect of medical treatment; MSA, metropolitan statistical area; NSAID, nonsteroidal anti-inflammatory drug; OR, odds ratio; PCP, primary care physician.

*Only initial visits for acute problems or follow-up visits for chronic problems were included.

†Adjusted for all variables shown.

There was an association between age and drugs ordered (P = .01) during primary LBP patient visits (Table 5). Drugs were ordered less often in the young (<25 years) than in the referent age category (25–44 years). Drugs were ordered more often among non-Whites (P = .01) and by primary care physicians (P = .01), particularly family (general) medicine physicians. Similarly, primary care physicians were more likely to order NSAIDs (P = .03), although osteopathic physicians were less likely to order NSAIDs than allopathic physicians (P = .004). There was an association between age and narcotic analgesic use (P = .05), with less use in older patients (>65 years) compared with the referent age category (25–44 years). Narcotic analgesics were prescribed less often in Hispanics (P = .01) and more often in non-MSAs (P = .03).

Conclusion

This study helps shed more light on LBP that motivates patients to seek medical care. More than 40% of LBP patient visits were provided by family (general) medicine physicians, comprising one of every 17 patient visits for this specialty. However, orthopedic surgeons provided a slightly greater percentage of LBP visits as part of their specialty case mix (1 of every 16 patient visits). Further, a substantial percentage of LBP patient visits (45%) were provided by non-primary care physicians. During 2003–2004 there were more than twice as many patient visits annually for LBP than reported in the 1990 NAMCS; however, the percentage of patient visits attributed to LBP (3%) and the percentage of LBP patient visits provided by primary care physicians (55%) remained remarkably similar to what was reported in the 1980s and early 1990s 20. Non-primary care services generally are considered inappropriate for patients with non-specific LBP 10. Thus, this study suggests that the recommended shift to primary care physicians for medical management of non-specific LBP has not occurred over the past two decades.

Injuries were the strongest risk factor associated with LBP patient visits (OR, 3.38; 95%, 2.75–4.14). There were also characteristic patterns of LBP patient visits according to age and geographic region. Patients other than those 25–44 years of age were less likely to seek medical care for LBP. Unavailable, and therefore uncontrolled, variables that could potentially explain the observed age distribution of LBP patient visits include occupational risk factors such as manual handling of materials, bending and twisting, whole-body vibration, and lifting for more than three-fourths of the work day 21. Patient visits for LBP were less likely to occur in the Midwest and South than in the Northeast (OR, 0.56; 95% CI, 0.40–0.77 for each contrast). It is unclear if these geographic findings reflect the epidemiology of LBP in the United States or if they are confounded by other uncontrolled variables. While relatively little is known about risk factors in the transition from acute to chronic LBP, this study suggests that injuries are not associated with progression of LBP.

Osteopathic physicians were more likely than allopathic physicians to provide medical care during LBP patient visits (OR, 2.61; 95% CI, 1.75–3.92). The physician specialties most likely to provide LBP patient visits were family (general) medicine, internal medicine, neurology, and orthopedic surgery. These findings are consistent with previous studies 1022. There was an even stronger association between osteopathic physicians and chronic LBP patient visits (OR, 4.39; 95% CI, 2.47–7.80). However, physician specialists in family (general) medicine, internal medicine, and neurology were not more likely than other physician specialists to provide chronic LBP patient visits. These findings, coupled with the greater use of shared physician care in chronic LBP (OR, 2.11; 95% CI, 1.30–3.44), suggest that osteopathic physicians are often used to complement the conventional medical management of chronic LBP by providing spinal manipulation.

At least eleven national clinical guidelines for LBP medical management in the primary care setting were published between 1994 and 2000 23. An updated review of national clinical guidelines summarized recommendations according to LBP chronicity 24. For acute LBP, radiographs were not considered useful for diagnosis of non-specific LBP. Recommended treatments included advising patients to remain active (although back-specific exercises were not considered effective), and ordering paracetamol or NSAIDs (muscle relaxants or narcotic analgesics may be considered as well). In contrast to acute LBP, few guidelines existed for the medical management of chronic LBP. Recently, however, European guidelines have been established for the management of chronic non-specific LBP 25. These guidelines do not recommend radiographs or other diagnostic imaging tests unless a specific cause is strongly suspected. They recommend brief educational interventions (specifically including supervised exercise therapy), cognitive behavioral therapy, and short-term use of NSAIDs or weak narcotic analgesics for pain relief. They generally do not recommend physical therapies (although spinal manipulation may be considered) or surgery (unless all other recommended conservative treatments have been tried and failed over a period of at least two years).

This study suggests that cognitive behavioral therapy (as proxied by mental health counseling) may be under-utilized in the medical management of chronic LBP (6% of patient visits), which is often characterized by depression and somatization 26. Nonsteroidal anti-inflammatory drugs were the most commonly used drugs for acute LBP (49% of patient visits); however, they were less likely to be used for chronic LBP (28% of patient visits). Non-narcotic analgesics were infrequently used for either acute or chronic LBP (6% of patient visits overall). The reported percentage of chronic back patients prescribed narcotic analgesics varies widely, from 3% to 66%, based on the treatment setting 27. The present study found the relevant percentage to be 28%. Almost two million surgical procedures (about one million annually) were ordered, scheduled, or performed during primary LBP patient visits. Not surprisingly, surgical procedures were more frequently associated with chronic LBP patient visits compared with acute LBP patient visits (OR, 12.62; 95% CI, 3.18–50.07). Together, the findings of this study reinforce the caricature of LBP medical care in the United States as being overspecialized, overinvasive, and overexpensive 10.

The medical management of LBP varies substantially between practitioners and countries 2428. Differences were observed in this study with regard to type of physician provider, physician specialty, and geographic region. Osteopathic physicians were less likely than allopathic physicians to order NSAIDs for LBP (OR, 0.43; 95% CI, 0.24–0.76). This is consistent with the theory that osteopathic physicians are less likely to prescribe drugs for LBP because they may use spinal manipulation as an alternative to drugs 29. Previous studies including an analysis of older NAMCS data 20 and a randomized controlled trial 30 have provided evidence to help support this theory. Family (general) medicine physicians were less likely to provide exercise counseling, but were more likely to order drugs for LBP. Time constraints during patient visits, particularly in a managed care environment, represent a possible explanation for the latter findings 31. Patient counseling was less often provided outside the Northeast in this study. A strong predictor of patient counseling, including exercise counseling, was having had an injury as the reason for seeking medical care for LBP (OR, 2.38; 95% CI, 1.50–3.77).

Although this study involved a large, nationally representative sample of patient visits for ambulatory medical care in the United States, there are several limitations of this study that should be noted. The study involved the epidemiology and medical management of LBP that was of a magnitude sufficient to prompt patients to visit physician offices for ambulatory medical care. Further, the study was limited by the NAMCS patient record form to patient visits in which LBP was among the three most important reasons for seeking medical care. Thus, this may more properly be considered a study of the epidemiology and medical management of clinically significant LBP in the ambulatory medical care environment. Although the measurement of incidence or prevalence rates was not an objective of the study, all patient visits in which LBP was recorded as a reason for seeking medical care were included in the epidemiological analyses to capture the maximal number of incident or prevalent LBP cases and thereby to provide more precise statistical estimates. Nevertheless, similar results were observed in the epidemiological analyses when only primary LBP patient visits were included (Table 1). The medical management analyses, however, were limited to only primary LBP patient visits to avoid potential confounding by other more important reasons for seeking medical care.

Simplifying assumptions were made in certain analyses because of limitations inherent in the NAMCS patient record form. Patient visits attributed to back (RFV code 1905) and low back (RFV code 1910) symptoms were combined because there were no substantive differences in the characteristics associated with these reported reasons for seeking medical care (Table 1). All patient visits attributed to back symptoms were assumed to involve back pain, although 4% of such visits involved unspecified back symptoms and another 2% involved such other back symptoms as cramps, contractures, spasms, limitation of movement or stiffness, or weakness. Similarly, with regard to etiology, all of the 19.7 million patient visits in which an IPA was reported (using a dichotomous patient record form item) were assumed to involve an injury, although in the subset of 8.4 million patient visits in which the specific IPA was described, up to 11% may have involved iatrogenic, environmental, or other etiologies. The elements of LBP medical management were assessed with survey items that asked whether the relevant element was "ordered, scheduled, or performed." However, it was impossible to confirm whether the reported elements actually occurred within the relevant patient visit or were eventually performed by the reporting physician.

Several analyses yielded imprecise results because they were based on less than 30 NAMCS patient visits or because the SE was greater than 30% of the NPE. Most often this occurred with less common characteristics (internal medicine physicians) or elements of LBP medical management (weight reduction and mental health counseling, physiotherapy, and surgical procedures), or in stratified (subgroup) analyses. Thus, racial minority groups were combined in a "non-White" group to partially overcome this limitation. Hospital admission could not be studied as an element of LBP medical management because of the limited number of observations.

In conclusion, this study found that the percentage of LBP visits provided by primary care physicians in the United States remains suboptimal. Medical management of LBP, particularly chronic LBP, appears to over-utilize surgery relative to more conservative measures such as patient counseling, non-narcotic analgesics, and other drug therapies. Osteopathic physicians are more likely to provide LBP care, and less likely to use NSAIDs during such visits, than their allopathic counterparts. In general, LBP medical management does not appear to be in accord with evidence-based guidelines.

Competing interests

JCL is Editor-in-Chief of Osteopathic Medicine and Primary Care. He was not involved in the review of the manuscript or in the editorial decision with regard to its suitability for publication.

Acknowledgements

This study was supported in part by grants from the National Institutes of Health – National Center for Complementary and Alternative Medicine (grant number K24AT002422) and the Osteopathic Heritage Foundation. Neither the National Institutes of Health nor the Osteopathic Heritage Foundation participated in the design and conduct of the study; collection, management, analysis, and interpretation of the data; or in the participation, review, or approval of the manuscript. The author reports no financial conflicts of interest.

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