Numerous clinical trials have investigated the effectiveness of interventions for low back pain (LBP). Despite the magnitude of research in this area, the evidence remains somewhat inconclusive for many of the more common interventions. One explanation offered for the uncertain nature of the evidence relates to the heterogeneous inclusion criteria used in many of the investigations. Simply speaking, many researchers fail to recognize that all patients with LBP are not the same, thus it is not reasonable to expect that all patients will benefit from identical interventions. Matching patients with interventions for which they are likely to benefit has been advocated as a method to improve the power of investigations.^1,2

      For decades, clinicians have attempted to assign patients to specific interventions based on their clinical presentation. Robin McKenzie, a New Zealand physical therapist, was one of the first to describe a classification approach that linked clinical presentation to interventions utilizing a patient’s directional preference³. In the approach advocated by McKenzie³ patients are requested to perform a series of movements and positions during the course of their examination. A directional preference is identified based on the direction of movement that improves the patient’s pain pattern. Essentially, if patients’ symptoms improve from a particular movement (i.e. flexion, extension, or side glide), they are treated with a series of movements and/or positions in that specific direction (directional preference). Researchers have since demonstrated the efficacy of this approach when patients are provided with interventions that match their directional preference.^4-6

      In one investigation, researchers classified patients according to their directional preference and reported superior outcomes in the group treated in accordance with their directional preference when compared with patients treated with interventions irrespective of their classification.⁶ Other researchers have proposed a broader classification criteria that bases physical therapy interventions on the patient’s clinical signs and symptoms.⁴ This approach is comparable to that of the McKenzie method, as patient outcomes using the classification system are superior to other methods of assigning interventions that do not directly consider the patient’s clinical presentation.^7,8

      Another means of selecting interventions based on a patient’s clinical presentation is through the use of clinical prediction rules (CPRs). CPRs have been developed as both a means of assisting clinicians in the diagnostic process and in the selection of optimum interventions.⁹ CPRs estimate the probability of a specific diagnostic outcome and may predict the prognosis from select interventions. Simply stated, CPRs may guide the clinician in the accurate diagnosis and selection of interventions.

      CPRs have been in existence for a few decades in the area of musculoskeletal medicine. Examples include the: 1) Ottawa ankle rules^10,11 (Table 1) designed to predict the need for ankle radiographs following injury and 2) the CPR for identifying deep vein thrombosis in the lower extremity (Table 2).¹² In addition to improving diagnostic utility, CPRs have been developed to assist clinicians in selecting optimum interventions such as spinal manipulation and stabilization.^13-15

      The purpose of this module is to briefly review the evolutionary history of CPRs, discuss the methodological standards for developing CPRs, review the hierarchy of evidence for applying CPRs in clinical practice, and to describe the spinal manipulation and stabilization CPRs currently in use for the management of patients with LBP.

Development of Clinical Prediction Rules

      The development of a CPR requires a series of three steps (Table 3) that includes derivation, validation, and impact analysis.⁹ Table 4 illustrates a hierarchical classification system used to describe the level of evidence that may be applied to CPRs based on their evolutionary stage of development. The levels of evidence in this classification range from 1 to 4, with Level 1 considered the highest based on the CPR having undergone all three steps of development. An example of a Level 1 CPR is the Ottawa Ankle Rule illustrated in Table 1. To date there are no CPRs for selecting physical therapy interventions that have reached a Level 1 on the evidence hierarchy. 

      Step One: Derivation. Step 1 involves derivation of the CPR using rigorous methodological standards as described in Table 5. Outcomes or predictors of interest are first identified and will typically include items (predictors of interest) from the history, examination, and diagnostic testing. An example of predictors may include symptom location, time passed since onset, or the results of special testing such as the straight leg raise. Researchers then must examine a group of patients and determine which of the predictors of interest are present in the individuals who have responded favorably to the intervention for which the CPRs are being investigated. Statistical analysis is then used to determine which of the predictors (present in the group who responded favorably to the intervention) are most accurate for use in the CPRs.⁹ Technically at this stage, the rules are classified as Level 4 evidence on the hierarchical system illustrated in Table 4, as they have not been validated. At this stage the CPR is not ready to be applied in a clinical setting with confidence; however, clinically important information may still be identified. Clinicians familiar with the CPR may alter practice patterns and in fact pay more attention to variables with good predictive power and place less emphasis on those variables that failed to show predictive power.⁹ At this time if the rule looks promising, investigators may move forward into the validation phase. 

      Step Two: Validation. Once researchers determine that a CPR has been derived from sound methodological standards (Table 5) and the results are not merely due to chance, the next step of validation is indicated. In Step 2, predictors used in the derivation stage must be validated in a different population. A key consideration in the validation process is to make sure the CPR performs well in a variety of settings, among different clinicians, and is not idiosyncratic to a single population. In other words, one may not assume that the results of a study conducted at one clinic by a single examiner would necessarily be valid in another setting or by a different examiner. For example, the patient population at a specific clinical setting that tends to see a sedentary non-athletic population may be more prone to spinal deconditioning, perhaps making them more likely to benefit from a conditioning program. A validation study that has been conducted in different settings among different clinicians would then be classified as a Level 2 CPR on the hierarchical system. A Level 2 CPR may be applied with confidence in various settings. 

      Step Three: Impact Analysis. Once CPRs are validated, an impact analysis must be performed to ascertain whether the rule has changed clinician behavior, improved patient outcomes, or reduced costs. For a CPR to progress to Level 1 of the evidence hierarchy, an impact analysis is necessary. Implementation of CPRs requires clinician time and effort; thus incorporation into clinical practice may be challenging. Part of this challenge may lie in the ability or desire of clinicians to practice outside of their normal daily routine or educational dogma. For example, clinicians may find it necessary to refer to publications or other written documentation to recall specific CPRs, requiring additional time they might not necessarily have during a patient’s visit. Moreover, clinicians may in fact find themselves withholding interventions that they routinely used for years. A CPR that is not incorporated into routine clinical practice with improved outcomes must be questioned, regardless of the accuracy or methodological standards used in the preceding derivation and validation steps.