Beyond the good prognosis. Examination of an inception cohort of patients with chronic low back pain

STUDY DESIGN: A 22-month prospective cohort study. OBJECTIVES: To describe the course of an inception cohort of patients with chronic low back pain. SUMMARY OF BACKGROUND DATA: Chronic low back pain is a debilitating condition with great medical and social cost. METHODS: A cohort of 1246 patients with acute low back pain who sought treatment from 208 North Carolina providers was observed. Patients who developed chronic low back pain were identified. Entry criteria were back pain of less than 10 weeks' duration, no previous care for this episode of low back pain, no previous spine surgery, not pregnant, no nonskin malignancy, and access to a telephone. The providers were of four types: primary care medical doctors, doctors of Chiropractic, orthopedic surgeons, and health maintenance organization-based primary care providers. Patients were contacted by telephone shortly after enrollment and at 2, 4, 8, 12, and 24 weeks, with a final interview at 22 months. Patient functional status, care-seeking, and satisfaction were evaluated. RESULTS: Ninety-six patients had chronic, continuous symptoms for 3 months, forming the inception cohort of chronic low back pain. A valid, reliable measure of back-specific functional disability also was used. Predictors of the development of chronicity were poor baseline functional status and sciatica. A more powerful predictor of chronicity was poor functional status at 4 weeks. Two thirds of patients with chronic low back pain at 3 months had functionally disabling symptoms at 22 months, and a majority of these were employed. Satisfaction with care was low. Forty-six patients (2.6% of the entire cohort) underwent surgery, with no statistically significant difference in surgical rates among initial provider strata. Patients who underwent surgery after 3 months had a Roland disability score at 22 months of 10 (7.7, 12.3). Forty-one percent of patients with chronic low back pain see an orthopedic or neurologic surgeon. Chronic low back pain occurs in 7.7% of patients who seek care for acute low back pain, with unremitting pain for 22 months in 4.7%. CONCLUSION: Once established, chronic low back pain is persistent. Most patients with chronic low back pain seek little care, and a majority are employed. Future research should emphasize maintenance of employment and function.     

Prognosis of chronic low back pain: design of an inception cohort study

Background

Although clinical guidelines generally portray chronic low back pain as a condition with a poor prognosis this portrayal is based on studies of potentially unrepresentative survival cohorts. The aim of this study is to describe the prognosis of an inception cohort of people with chronic low back pain presenting for primary care.

Methods/Design

The study will be an inception cohort study with one year follow-up. Participants are drawn from a cohort of consecutive patients presenting with acute low back pain (less than 2 weeks duration) to primary care clinics in Sydney, Australia. Those patients who continue to experience pain at three months, and are therefore classified as having chronic back pain, are invited to participate in the current study. The cohort will be followed up by telephone at baseline, 9 months and 12 months after being diagnosed with chronic low back pain. Recovery from low back pain will be measured by sampling three different outcomes: pain intensity, interference with function due to pain, and work status. Life tables will be generated to determine the one year prognosis of chronic low back pain. Prognostic factors will be assessed using Cox regression.

Discussion

This study will determine the prognosis of chronic non-specific low back pain in a representative cohort of patients sourced from primary care. The results of this study will improve understanding of chronic low back pain, allowing clinicians to provide more accurate prognostic information to their patients.     

Where do people acquire their beliefs about low back pain?

Back pain is a ubiquitous health issue across the globe. Beliefs of patients and health care providers play an important role in the development of chronic back pain and associated disability, as well as subsequent recovery. Recent published literature highlight that beliefs about back pain among the community and health care practitioners are inconsistent with current evidence. Presence of back pain myths negatively impacts individual's back-related behavior in general and may be amplified by the consulting health care provider. Our narrative of the sources of back pain is based on the current literature and reveals our position as practicing physiotherapists who are dealing with back pain patients.     

An updated overview of clinical guidelines for the management of non-specific low back pain in primary care

The aim of this study was to present and compare the content of (inter)national clinical guidelines for the management of low back pain. To rationalise the management of low back pain, evidence-based clinical guidelines have been issued in many countries. Given that the available scientific evidence is the same, irrespective of the country, one would expect these guidelines to include more or less similar recommendations regarding diagnosis and treatment. We updated a previous review that included clinical guidelines published up to and including the year 2000. Guidelines were included that met the following criteria: the target group consisted mainly of primary health care professionals, and the guideline was published in English, German, Finnish, Spanish, Norwegian, or Dutch. Only one guideline per country was included: the one most recently published. This updated review includes national clinical guidelines from 13 countries and 2 international clinical guidelines from Europe published from 2000 until 2008. The content of the guidelines appeared to be quite similar regarding the diagnostic classification (diagnostic triage) and the use of diagnostic and therapeutic interventions. Consistent features for acute low back pain were the early and gradual activation of patients, the discouragement of prescribed bed rest and the recognition of psychosocial factors as risk factors for chronicity. For chronic low back pain, consistent features included supervised exercises, cognitive behavioural therapy and multidisciplinary treatment. However, there are some discrepancies for recommendations regarding spinal manipulation and drug treatment for acute and chronic low back pain. The comparison of international clinical guidelines for the management of low back pain showed that diagnostic and therapeutic recommendations are generally similar. There are also some differences which may be due to a lack of strong evidence regarding these topics or due to differences in local health care systems. The implementation of these clinical guidelines remains a challenge for clinical practice and research.     

Bridging the gap between science and practice in managing low back pain. A comprehensive spine care system in a health maintenance organization setting

STUDY DESIGN: A case study of spine care system changes in a multispecialty group practice health maintenance organization setting. OBJECTIVES: To reduce unnecessary use of imaging and specialty referrals for low back pain in the primary care setting and to reduce spine surgery rates. SUMMARY OF BACKGROUND DATA: Results of previous research indicate that diagnostic and therapeutic procedures for low back pain are frequently used even though there is no scientific evidence of their efficacy. This indicates that low back pain care can be made more efficient by reducing the use of unproven diagnostic and therapeutic interventions for low back pain. METHODS: Rates of diagnostic imaging and specialty referral rates for low back pain were monitored for 9 months before and 9 months after primary care physician education regarding appropriate low back pain evaluation and management. Spine surgery rates were also monitored before and after implementation of a nonsurgical spine clinic. RESULTS: Large reductions in rates of imaging and specialty referrals for low back pain were achieved after primary care physician education. After spine clinic implementation, visits to spine surgeons dropped by approximately 50%, and spine surgery rates per thousand health plan members were reduced by 35%. CONCLUSIONS: Primary care physician education regarding low back pain management can reduce use of imaging and specialty referrals without reductions in patient satisfaction, and implementation of a nonsurgical spine clinic for complex or chronic spine patients can significantly reduce spine surgery consultations and spine surgery rates.     

Differential diagnosis of spondylolysis in a patient with chronic low back pain

STUDY DESIGN: Resident's case problem. BACKGROUND: A 26-year-old male sought physical therapy services via direct access secondary to a flare-up of a chronic low back pain condition. The patient complained of recent onset of lumbosacral joint pain, including (1) constant right-sided deep-bruise sensation, (2) intermittent right-sided sharp stabbing pain, and (3) constant bilateral aching. The patient's past medical history included a hyperextension low back injury while playing football at age 17. Physical examination revealed (1) deep pain with palpation over the right lumbosacral joint region, (2) sharp right lumbosacral joint pain with 1 repetition of active trunk backward bending, and (3) a marked increase in pain and joint hypomobility with right unilateral joint assessment at the L4 and L5 spinal levels. DIAGNOSIS: The examining therapist referred the patient for radiographic evaluation due to strong suspicions of a pars interarticularis bony defect. Lumbar plain films, oblique views, revealed an L5 bilateral pars defect, leading to a diagnosis of a longstanding bilateral L5 spondylolysis. DISCUSSION: Patients with low back pain often seek physical therapy services. Identification of pathology requiring examination by other health care providers, leading to patient referral to other health care practitioners, is a potential important outcome of the therapist's examination. This resident's case problem illustrates the importance of a systematic examination scheme, including a thorough medical screening component that led to a patient referral for radiographic evaluation. The resultant diagnosis, although not representing serious pathology, did impact the therapist's patient plan of care.     

Comfortably numb? Exploring satisfaction with chronic back pain visits

Background contextChronic back pain is a condition characterized by high rates of disability, health-care service use, and costs.PurposeThe purpose of this study was to identify factors associated with patients' satisfaction with their last health-care provider visit for chronic low back pain (LBP).Study design/settingA cross-sectional, state-level, telephone survey was administered to patients with chronic LBP.Patient sampleThe sample consisted of 624 individuals with chronic LBP who reported seeing a health-care provider in the previous year.Outcome measuresDependent variables included satisfaction with last visit for LBP and intent to seek care from additional providers. Independent variables included the Roland-Morris Disability Questionnaire, 3-month pain ratings using a 0 to 10 Likert scale, the Medical Outcomes Survey Short Form 12, and self-reported health service utilization (provider type, number of visits to health-care providers, medication use during the previous month, and treatments and diagnostic tests during the previous year).MethodsBivariate and multivariate analyses were used to explore how demographic, insurance-related, and health-related characteristics were associated with patient satisfaction.ResultsParticipants who were not satisfied with one or more aspects of their last clinic visit were younger (51.0 vs. 54.21 years), reported higher 3-month pain ratings (7.23 vs. 6.53), and were more commonly Hispanic (53.2% vs. 46.8% for other ethnicities) and uninsured (43.1% vs. 29.3% for other insurance groups). Those who intended to seek care from additional providers were younger (50.05 vs. 55.49 years), had higher 3-month pain ratings (7.20 vs. 6.46), had lower Short Form 12 mental health component scores (44.75 vs. 49.55) and physical component scores (30.07 vs. 31.55), and were more commonly black (54.6% vs. 45.4% for other racial groups) and uninsured (56.9% vs. 43.1% for other insurance groups). Narcotic use was associated with satisfaction (odds ratio=2.12, p=.01), whereas lack of insurance was associated with respondents' intent to seek care from additional providers (odds ratio=2.97, p<.01).ConclusionsFactors other than disability were associated with satisfaction with chronic LBP visits. Understanding the role of medication in satisfaction and its implications for the health behaviors of this highly disabled population may be particularly important.     

Cost-effectiveness of general practice care for low back pain: a systematic review

Care from a general practitioner (GP) is one of the most frequently utilised healthcare services for people with low back pain and only a small proportion of those with low back pain who seek care from a GP are referred to other services. The aim of this systematic review was to evaluate the evidence on cost-effectiveness of GP care in non-specific low back pain. We searched clinical and economic electronic databases, and the reference list of relevant systematic reviews and included studies to June 2010. Economic evaluations conducted alongside randomised controlled trials with at least one GP care arm were eligible for inclusion. Two reviewers independently screened search results and extracted data. Eleven studies were included; the majority of which conducted a cost-effectiveness or cost-utility analysis. Most studies investigated the cost-effectiveness of usual GP care. Adding advice, education and exercise, or exercise and behavioural counselling, to usual GP care was more cost-effective than usual GP care alone. Clinical rehabilitation and/or occupational intervention, and acupuncture were more cost-effective than usual GP care. One study investigated the cost-effectiveness of guideline-based GP care, and found that adding exercise and/or spinal manipulation was more cost-effective than guideline-based GP care alone. In conclusion, GP care alone did not appear to be the most cost-effective treatment option for low back pain. GPs can improve the cost-effectiveness of their treatment by referring their patients for additional services, such as advice and exercise, or by providing the services themselves.     

The pain epidemiology

Acute pain is the most common symptom for which patients seek medical care. Chronic pain is severe and frequent health care problem in terms of patient suffering and economic implications for the society. More than half of chronic pain related to musculoskeletal pain. Epidemiological studies on pain are limited by inconsistencies in definition, identification, and evaluation. The reported prevalence ranges from 8 to 80%. A World Health Organization Study in Primary Care showed persistent pain in 22% of primary care patients and Survey of chronic pain in Europe showed chronic pain in 19%. Because, the large variation in frequency and the inconsistent relationship between persistent pain and disability we need to consider the global concept of chronic pain with implications for management and prognosis. Epidemiological research should have as goal the development effective healthcare interventions through better understanding of pain, impact on the individual and society.     

Intensive group training protocol versus guideline physiotherapy for patients with chronic low back pain: a randomised controlled trial

Intensive group training using principles of graded activity has been proven to be effective in occupational care for workers with chronic low back pain. Objective of the study was to compare the effects of an intensive group training protocol aimed at returning to normal daily activities and guideline physiotherapy for primary care patients with non-specific chronic low back pain. The study was designed as pragmatic randomised controlled trial with a setup of 105 primary care physiotherapists in 49 practices and 114 patients with non-specific low back pain of more than 12 weeks duration participated in the study. In the intensive group training protocol exercise therapy, back school and operant-conditioning behavioural principles are combined. Patients were treated during 10 individual sessions along 20 group sessions. Usual care consisted of physiotherapy according to the Dutch guidelines for Low Back Pain. Main outcome measures were functional disability (Roland Morris disability questionnaire), pain intensity, perceived recovery and sick leave because of low back pain assessed at baseline and after 6, 13, 26 and 52 weeks. Both an intention-to-treat analysis and a per-protocol analysis were performed. Multilevel analysis did not show significant differences between both treatment groups on any outcome measures during the complete follow-up period, with one exception. After 26 weeks the protocol group showed more reduction in pain intensity than the guideline group, but this difference was absent after 52 weeks. We finally conclude that an intensive group training protocol was not more effective than usual physiotherapy for chronic low back pain.     

Multidisciplinary biopsychosocial rehabilitation for subacute low back pain in working-age adults: a systematic review within the framework of the Cochrane Collaboration Back Review Group

STUDY DESIGN: A systematic review of randomized controlled trials was performed. OBJECTIVE: To evaluate the effectiveness of multidisciplinary biopsychosocial rehabilitation for subacute low back pain among working-age adults. SUMMARY OF BACKGROUND DATA: Multidisciplinary biopsychosocial rehabilitation programs are widely applied for patients with chronic low back pain. The multidisciplinary biopsychosocial approach for prolonged low back pain could be considered to prevent chronicity. Work site visits and a close relationship with occupational health care might produce results in terms of patients working ability. METHODS: Reviewed randomized controlled trials as well as controlled trials were identified from electronic bibliographic databases, reference checking, and consultation with experts in the rehabilitation field. Four blinded reviewers selected the trials. Two rehabilitation specialists evaluated the clinical relevance. Two other blinded reviewers extracted the data and assessed the main results along with the methodologic quality of the studies. A qualitative analysis was performed to evaluate the level evidence. RESULTS: Of 1808 references, only 2 relevant studies were included. Both were considered to be methodologically low-quality randomized controlled trials. The clinical relevance of the studies was sufficient. The level of scientific evidence was moderate, showing that multidisciplinary rehabilitation involving work site visit or more comprehensive occupational health care intervention helps patients return to work faster, makes sick leaves less, and alleviates subjective disability. CONCLUSIONS: There is moderate evidence showing that multidisciplinary rehabilitation for subacute low back pain is effective, and that work site visit increases the effectiveness, but because the analyzed studies had some methodologic shortcomings, an obvious need still exists for high-quality trials in this field.     

Recommandations européenes (COST B 13) en matiè de prévention et de prise en charge de la lombalgie non spécifique

Objectives. To produce guidelines based on scientific evidence for the management of low back pain. These guidelines were developed within the framework of the COST Action B13 “Low back pain : guidelines for its management”, issued by the European Commission, Research Directorate-general, Department of Policy, Coordination and Strategy.Methods. Thirty eight experts in the field of low back pain coming from 13 different European countries have contributed to these guidelines. The experts were assigned to three working groups. The group 1 has formulated guidelines for the management of acute low back pain, the group 2 has developed guidelines for the management of chronic low back pain and, finally, the group 3 has proposed guidelines for the prevention in low back pain. The evidence underpinning the guidelines was retrieved through systematic searches of the scientific literature up to the end 2003. Systematic review, randomised controlled trials, and existing guidelines were included. The methodological quality of the selected articles was evaluated using the scoring system developed by the “Cochrane Back Review Group”.Results and conclusion. This paper is a summary in French of the recommendations based on scientific evidence that should be taken into consideration by physicians, health care providers and policy makers when dealing with patients suffering from low back pain. Nevertheless, many aspects of care need to be validated before recommendations can be issued.     

The course of pain drawings during a 10-week treatment period in patients with acute and sub-acute low back pain

Background  

Pain drawings are widely used as an assessment of patients' subjective pain in low back pain patients being considered for surgery. Less work has been done on primary health care patients. Moreover, the possible correlation between pain drawing modalities and other pain assessment methods, such as pain score and functional variables needs to be described. Thus, the objectives were to describe the course of pain drawings during treatment in primary health care for low back pain patients.     

Tai chi and chronic pain

In the last 2 decades, a growing body of research aimed at investigating the health benefits of Tai Chi in various chronic health conditions has been recognized in the literature. This article reviewed the history, the philosophy, and the evidence for the role of Tai Chi in a few selected chronic pain conditions. The ancient health art of Tai Chi contributes to chronic pain management in 3 major areas: adaptive exercise, mind-body interaction, and meditation. Trials examining the health benefit of Tai Chi in chronic pain conditions are mostly low quality. Only 5 pain conditions were reviewed: osteoarthritis, fibromyalgia, rheumatoid arthritis, low back pain, and headache. Of these, Tai Chi seems to be an effective intervention in osteoarthritis, low back pain, and fibromyalgia. The limitations of the Tai Chi study design and suggestions for the direction of future research are also discussed.     

Relative contribution of mental health and exercise-related pain increment to treadmill test intolerance in patients with chronic low back pain.

STUDY DESIGN: A cross-sectional study. OBJECTIVES: To determine the relative contribution of pain increase and mental health to testing performance during a single bout of exercise in patients with chronic low back pain. BACKGROUND: Controversy exists as to which factors principally limit physical performance in patients with chronic low back pain. Some believe psychological factors limit physical performance, whereas others believe activity-related increases in pain intensity limit performance. METHODS: Seventy-five patients with chronic low back pain reported pain intensity before and after undergoing a maximal, symptom-limited modified treadmill test. Walking time (in minutes) and aerobic fitness were measured. The Short Form 36 Health Survey was administered to all patients. RESULTS: Fifty-four percent of the sample stopped testing because of a significant increase in pain intensity (P = 0.0001). Treadmill performance was lower in patients who stopped because of pain than in those who stopped because of fatigue (P = 0.02). The patients who stopped because of pain were also more likely to have low mental health as assessed by the Short Form 36 Health Survey. Low mental health, however, did not have a statistically significant influence on treadmill performance. CONCLUSION: The data indicate that impairment of physical performance during treadmill testing in patients with chronic low back pain is attributable to testing-induced increase in pain intensity rather than to individual low mental health scores.     

Prognosis of acute low back pain: design of a prospective inception cohort study

Background  

Clinical guidelines generally portray acute low back pain as a benign and self-limiting condition. However, evidence about the clinical course of acute low back pain is contradictory and the risk of subsequently developing chronic low back pain remains uncertain. There are few high quality prognosis studies and none that have measured pain, disability and return to work over a 12 month period. This study aims to provide the first estimates of the one year prognosis of acute low back pain (pain of less than 2 weeks duration) in patients consulting primary care practitioners. A secondary aim is to identify factors that are associated with the prognosis of low back pain.     

Communication style and exercise compliance in physiotherapy (CONNECT). A cluster randomized controlled trial to test a theory-based intervention to increase chronic low back pain patients' adherence to physiotherapists' recommendations: study rationale, design, and methods

ABSTRACT: BACKGROUND: Physical activity and exercise therapy are among the accepted clinical rehabilitation guidelines and are recommended self-management strategies for chronic low back pain. However, many back pain sufferers do not adhere to their physiotherapist's recommendations. Poor patient adherence may decrease the effectiveness of advice and home-based rehabilitation exercises. According to self-determination theory, support from health care practitioners can promote patients' autonomous motivation and greater long-term behavioral persistence (e.g., adherence to physiotherapists' recommendations). The aim of this trial is to assess the effect of an intervention designed to increase physiotherapists' autonomy-supportive communication on low back pain patients' adherence to physical activity and exercise therapy recommendations. METHODS: This study will be a single-blinded cluster randomized controlled trial. Outpatient physiotherapy centers (N =12) in Dublin, Ireland (population = 1.25 million) will be randomly assigned using a computer-generated algorithm to either the experimental or control arm. Physiotherapists in the experimental arm (two hospitals and four primary care clinics) will attend eight hours of communication skills training. Training will include handouts, workbooks, video examples, role-play, and discussion designed to teach physiotherapists how to communicate in a manner that promotes autonomous patient motivation. Physiotherapists in the waitlist control arm (two hospitals and four primary care clinics) will not receive this training. Participants (N = 292) with chronic low back pain will complete assessments at baseline, as well as 1 week, 4 weeks, 12 weeks, and 24 weeks after their first physiotherapy appointment. Primary outcomes will include adherence to physiotherapy recommendations, as well as low back pain, function, and well-being. Participants will be blinded to treatment allocation, as they will not be told if their physiotherapist has received the communication skills training. Outcome assessors will also be blinded.We will use linear mixed modeling to test between arm differences both in the mean levels and the rates of change of the outcome variables. We will employ structural equation modeling to examine the process of change, including hypothesized mediation effects. DISCUSSION: This trial will be the first to test the effect of a self-determination theory-based communication skills training program for physiotherapists on their low back pain patients' adherence to rehabilitation recommendations. Trial Registration Current Controlled Trials ISRCTN63723433.     

Chronic low back pain in individuals with chronic neck pain of traumatic and non-traumatic origin: a population-based study

BACKGROUND: It is unclear whether the prevalence of chronic low back pain is higher in chronic whiplash patients than in the general population. In a population-based study, we evaluated the prevalence of chronic low back pain in individuals with chronic neck pain of traumatic and non-traumatic origin, with special emphasis on whiplash injury. SUBJECTS AND METHODS: Additional questions concerning the patient's experience of neck and low back pain were added to the questionnaire of the MONICA health survey. 4,415 subjects aged 25-64 years were randomly selected from a geographically well-defined area in northern Sweden. RESULTS: The prevalences of chronic low back pain and chronic neck pain were 16% and 17%, respectively. 51% of subjects had both back and neck pain. Of the patients with neck pain, one quarter had a history of neck injury, which was related to whiplash injury in almost one-half of the cases. The prevalence of chronic low back pain in individuals with chronic non-traumatic neck pain was 53%, and it was 48% in those with chronic neck pain and a history of neck trauma. There was no difference in the prevalence of chronic low back pain between whiplash injury and other types of neck trauma. Confounding factors such as sex, age, marital status, BMI, smoking status and level of education were not significantly different between traumatic and non-traumatic groups. INTERPRETATION: Independently of traumatic or non-traumatic origin of the symptoms, the prevalence of chronic low back pain is 3 times higher in individuals with chronic neck pain than in the general population. Causes other than a history of neck trauma, such as chronic muskuloskeletal pain syndromes, may be important in evaluation of these cases.     

Exercise therapy for low back pain: a systematic review within the framework of the cochrane collaboration back review group

STUDY DESIGN: A systematic review of randomized controlled trials was performed. SUMMARY OF BACKGROUND DATA: Exercise therapy is a widely used treatment for low back pain. OBJECTIVES: To evaluate the effectiveness of exercise therapy for low back pain with regard to pain intensity, functional status, overall improvement, and return to work. METHODS: The Cochrane Controlled Trials Register, Medline, Embase, PsycLIT, and reference lists of articles were searched. Randomized trials testing all types of exercise therapy for subjects with nonspecific low back pain with or without radiation into the legs were included. Two reviewers independently extracted data and assessed trial quality. Because trials were considered heterogeneous with regard to study populations, interventions, and outcomes, it was decided not to perform a meta-analysis, but to summarize the results using a rating system of four levels of evidence: strong, moderate, limited, or none. RESULTS: In this review, 39 trials were identified. There is strong evidence that exercise therapy is not more effective for acute low back pain than inactive or other active treatments with which it has been compared. There is conflicting evidence on the effectiveness of exercise therapy compared with inactive treatments for chronic low back pain. Exercise therapy was more effective than usual care by the general practitioner and just as effective as conventional physiotherapy for chronic low back pain. CONCLUSIONS: The evidence summarized in this systematic review does not indicate that specific exercises are effective for the treatment of acute low back pain. Exercises may be helpful for patients with chronic low back pain to increase return to normal daily activities and work.     

Predictors of efficacy in treatment of chronic low back pain

The investigation of predictors for therapy outcome in patients with chronic low back pain date back to the early 1970s. Numerous well controlled prospective longitudinal studies have confirmed the predominant predictive power of several psychological factors, which are in addition to objective work related, medical and sociodemographic variables. Studies published in the review period have reported markedly improved methodological standards. Further progress is seen with the enhanced search for predictors of working situation in chronic low back pain patients. Finally, there is a shift toward the investigation of predictors for efficacy of primary care in acute and subchronic low back pain patients.