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Research Review By Dr. Michael Haneline©

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Date Posted:

August 2017

Study Title:

Clinical classification in low back pain: best-evidence diagnostic rules based on systematic reviews

Authors:

Petersen T, Laslett M & Juhl C

Author's Affiliations:

Back Center Copenhagen, Denmark; PhysioSouth Ltd, Christchurch, New Zealand; Southern Musculoskeletal Seminars, Christchurch, New Zealand; Research Unit for Musculoskeletal Function and Physiotherapy, Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark; Department of Rehabilitation, University Hospital of Copenhagen, Denmark.

Publication Information:

BMC Musculoskeletal Disorders 2017; 18:188. DOI 10.1186/s12891-017-1549-6

Background Information:

Researchers for quite some time have suggested that the ability to identify subgroups of patients with low back pain (LBP) based on diagnostic, prognostic and treatment characteristics would be useful. Until now, psychosocial factors have been the main consideration vis-à-vis the biopsychosocial model, and numerous studies have explored how these factors can interfere with recovery. As a result, a body of evidence supports the predictive value of a set of psychosocial factors which point to poorer outcome in LBP patients.

On the other hand, a structural/pathoanatomical focus is common among clinicians in the process of diagnostic interpretation, though it is also an important aspect of the biopsychosocial model (1). Research has not shown that treatments targeting psychosocial factors are particularly beneficial, however, and there is little evidence that psychosocial treatments are more effective than other types of treatment.

The authors of this study suggest it is time to place research emphasis on the “bio” aspect of the biopsychosocial model, because the ability to choose the most effective treatment for a given patient may not be possible without a better understanding of the biological component. They were interested in identifying signs and symptoms that had the potential to diagnose common sources of LBP, for instance: intervertebral discs, sacroiliac joints, facet joints, bones, nerve roots, muscles, etc.

The term Clinical Diagnostic (or, Decision) Rule (CDR) was used, which can be defined as “a clinical tool that quantifies the individual contributions that various components of the history, physical examination, and basic laboratory results make toward the diagnosis, prognosis, or likely response to treatment in a patient. Clinical decision rules attempt to formally test, simplify, and increase the accuracy of clinicians’ diagnostic and prognostic assessments” (2).

The purpose of this study was to develop multi-faceted CDRs for the lumbar spine using diagnostic accuracy scores from a variety of tests for use by primary care clinicians as well as researchers. The individual clinical examination findings would be clustered to form CDRs based on well-defined criteria.

Pertinent Results:

The diagnostic value of findings for categories representing ten anatomical sites and/or conditions were presented – they are listed below.

Intervertebral Disc:
The included evidence was considered sufficient to constitute a clinical decision rule (CDR); therefore, the use of centralization of symptoms (change of pain in the furthermost whole-body region) during physical examination was recommended. High positive likelihood ratios (LRs) were found in 2 studies, indicating that a positive test would be useful for ruling in the diagnosis.

Facet Joint:
Although findings from 10 studies were used to make the decision, the evidence was judged insufficient to constitute a CDR.

Sacroiliac Joint:
The evidence from 7 studies led to the conclusion that there is sufficient evidence to constitute a CDR; in particular, the Laslett rule was recommended. The Laslett rule is comprised of at least 3 positive out of 5 of the following physical examination findings:
  1. distraction,
  2. compression,
  3. thigh thrust,
  4. Gaenslen’s test, and
  5. sacral thrust.
The authors recommended adding ‘no centralization’ from the “Laslett composite” to the CDR, as well as the physical examination finding of dominant pain in the posterior superior iliac spine (PSIS) area.

Disc Herniation with Nerve Root Involvement:
The evidence is sufficient to constitute a CDR, but the authors recommend the use of the straight leg raise (SLR) test in combination with the Hancock rule comprising at least 3 positive out of 4 of the following findings:
  1. dermatomal pain location in concordance with a nerve root,
  2. corresponding sensory deficit,
  3. diminished reflex, and
  4. motor weakness.
Spinal Stenosis:
The evidence is sufficient to establish a CDR with a recommendation to use the Cook rule, comprising at least 3 positive out of 5 of the following findings from the patient history:
  1. age more than 48 years,
  2. bilateral symptoms,
  3. leg pain more than back pain,
  4. pain during walking/standing, and
  5. pain relief upon sitting.
Spondylolisthesis:
The evidence is sufficient to constitute a CDR, with a recommendation to use a combination of two positive physical examination findings:
  1. intervertebral slip by inspection or palpation and
  2. segmental hypermobility by use of manual passive physiological intervertebral motion test.
The use of the passive lumbar extension test was also recommended as a supplement for the identification of degenerative spondylolisthesis in the elderly.

Fracture:
The evidence is insufficient to constitute a CDR. There is a potential benefit of the Henschke rule, however, which consists of 1 negative out of 3 of the following findings from patient history:
  1. age > 70 years,
  2. prolonged use of corticosteroids, and
  3. significant trauma.
Nonetheless, the Henschke rule is based on a single study and has not yet been validated in other studies.

Myofascial Pain:
No acceptable evidence was located regarding diagnostic value because available studies in the field have lacked an adequate diagnostic reference standard. Furthermore, there is substantial variability of criteria used to diagnose a Myofascial Pain Syndrome (MPS), none of which have been validated.

The authors suggest a composite of three minimum criteria that support a diagnosis of MPS:
  1. presence of a palpable taut band within a skeletal muscle,
  2. presence of a hypersensitive spot within the taut band, with or without reproduction of a distinct referred pain sensation with stimulation of the spot,
  3. patient recognition of the elicited pain.
When no reference standard exists with which to validate a given test, at least intra- and inter-observer reliability should be acceptable. However, no data currently exists that supports the ability of different examiners to agree on the exact location of a Trigger Point within a specific muscle.

Peripheral Nerve:
There is no available evidence regarding diagnostic value because of the lack of an acceptable diagnostic reference standard. The authors suggested several criteria that could be used in future diagnostic studies: Patient recognition of usual lumbar or leg pain with at least two stages of sensitizing maneuvers, such as knee extension, ankle dorsiflexion, or neck flexion during straight leg raise or the slump test. These criteria were suggested even though there is substantial variability of criteria used to diagnose increased peripheral neural mechanosensitivity (3). On the other hand, three studies of the inter-tester reliability of patient recognition of lumbar or leg pain with at least two stages of sensitizing maneuvers have been performed. Kappa values were high in each of these studies, pointing to substantial agreement between examiners.

Central Sensitization:
The evidence is insufficient to generate a diagnostic rule to identify patients with a condition characterized by “increased responsiveness of nociceptive neurons in the central nervous system to their normal or subthreshold afferent input”. A systematic literature search was not even conducted regarding central sensitization (CS) because related studies have been hampered by the lack of an adequate diagnostic reference standard.

Given the lack of a diagnostic rule, the authors suggest using the consensus-based Nijs rule to support the diagnosis of CS. The first step in Nijs rule is to exclude a neuropathic pain source, followed by step 2 which is to make sure that several of the criteria listed below are met. Criterion 1 must be satisfied, in combination with either criterion 2 or 3:
  • Criterion 1: Pain experience disproportionate to the nature and extent of injury or pathology (i.e. not sufficient evidence of injury), or objective dysfunctions capable of generating nociceptive input consistent with the patient’s severity of pain and disability.
  • Criterion 2: At least one of the following patterns present:
    1. Bilateral pain/mirror pain (i.e. symmetrical pain pattern)
    2. Pain varying in (anatomical) location/travelling pain to anatomical locations unrelated to the presumed source of nociception (ex. hemilateral pain), large pain areas with non-segmental (i.e. neuroanatomically illogical) distribution
    3. Widespread pain (defined as pain located axially, on the left and right side of the body and both above and below the waist)
    4. Allodynia/hyperalgesia outside the segmental area of presumed nociception. These findings are based on testing of light touch as well as testing by pin prick or pressure (hyperalgesia).
  • Criterion 3: Hypersensitivity of senses unrelated to the muscular system. These findings are based on a score of at least 40 on the Central Sensitization Inventory. (4)

Clinical Application & Conclusions:

Below is a list of CDRs that the authors considered to be promising, though their accuracy in a primary care setting has not yet been confirmed.

Intervertebral Disc:
  • Centralization of symptoms
Sacroiliac Joint:
  • No centralization of symptoms
  • Dominant pain in SIJ, but not the ischial tuberosity area
  • 3 positive out of 5 physical examination findings: distraction, compression, thigh thrust, Gaenslen's test, sacral thrust
Disc Herniation with Nerve Root Involvement:
  • Straight leg raise test positive for referred leg pain
  • 3 positive out of 4 history or physical examination findings: dermatomal pain location in concordance with a nerve root, and corresponding sensory deficits, reflex and motor weakness
  • Supplementary physical examination finding: Crossed straight leg raise test positive
Spinal Stenosis:
  • 3 positive out of history findings: age more than 48 years, bilateral symptoms, leg pain more than back pain, pain during walking\standing, or pain relief upon sitting
  • Supplementary physical examination finding: improved walking tolerance with the spine in flexion or relief by forward bending
Spondylolisthesis:
  • Intervertebral slip by inspection or palpation
  • Segmental hypermobility by use of manual passive physiological inter-vertebral motion test
  • Supplementary physical examination finding in the elderly: Passive leg extension test positive

Study Methods:

This was a review paper that was based on the Preferred Reporting Items for Systematic reviews and Meta-analyses statement (also referred to as PRISMA). Both systematic reviews and original studies were included. Searches were conducted of the PubMed, Embase, and CINAHL databases; also, reference lists from included papers were reviewed for additional studies.

Titles and abstracts were inspected to find studies that compared the results of clinical examination findings of LBP patients with those of diagnostic reference standards and those that appeared to meet the inclusion criteria were selected for full text review.

To be included in the review, the following criteria had to be met:
  • Participants had LBP with or without leg pain.
  • Use of an appropriate reference standard.
  • Evaluation of at least one clinical finding available to primary care clinicians.
  • Presentation of data enabling calculation of sensitivity and specificity.
The full text of original studies was independently scored by 2 authors for quality and risk of bias using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) instrument. Disagreements were resolved by discussion.

To be included this review’s final recommendations, the diagnostic values in more than two thirds of relevant studies had to agree. Recommendations were downgraded from strong to weak when there was serious risk of bias.

The diagnostic accuracy measures had to be clinically useful, which was defined as having a positive likelihood ratio (LR) above 2.0. This means that the results of having a positive test would at least double the ratio of having the target disorder compared to not having the disorder. Furthermore, a clinical finding that would be used to rule out the disorder had to be a negative LR below 0.5, which means a negative test reduces the odds of having the disorder by at least half compared to not having the disorder.

Study Strengths / Weaknesses

There are currently no ‘gold’ standard tests for the patho-anatomical disorders that were covered in this review. However, reference standards are available that are considered appropriate and suitable for most patients. These reference standards are also acceptable comparators for use in diagnostic accuracy studies.

The literature search was not updated to year 2015 in all diagnostic categories because of limited resources.

Most patients in the included studies were preselected, usually having been referred to specialist centers for diagnostic evaluation; thus, they would be more likely to have the target disorder. The tests would possibly perform differently in the typical primary care setting.

The data were not pooled because of the high degree of variability across studies. Said variability was due to substantial differences between studies regarding patient characteristics, prevalence of the target disorders, the reference standard that was used, and the way index tests were performed. In addition, the definition of a positive reference standard was not typically given and probably differed among studies.

Additional References:

  1. Ford J, Hahne A. Pathoanatomy and classification of low back disorders. Man Ther. 2013; 18: 165–8.
  2. McGinn TG, Guyatt GH, Wyer PC, Naylor CD, Stiell IG, Richardson WS. Users’ guides to the medical literature: XXII: how to use articles about clinical decision rules. Evidence-Based Medicine Working Group. JAMA. 2000; 284(1): 79–84.
  3. Dixon JK, Keating JL. Variability in straight leg raise measurements. Physiother. 2000; 86(7): 361–70.
  4. Neblett R, Cohen H, Choi Y, Hartzell MM, Williams M, Mayer TG, et al. The Central Sensitization Inventory (CSI): establishing clinically significant values for identifying central sensitivity syndromes in an outpatient chronic pain sample. J Pain. 2013; 14(5): 438–45.

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