Clinical perspective: how do clinical test results differentiate chronic and subacute low back pain patients from "non-patients"?

Our limited understanding of underlying conditions for back pain is reflected in the common use of pain-duration-based groupings. The aim of this paper was to investigate typical clinical tests used in examining low back pain (LBP) patients in order to discover how tests distinguish between chronic low back pain patients (CLBP) and subacute low back pain patients (SLBP) and if they distinguish these groups from those with no "patient status." CLBP patients in this study were from a university hospital and SLBP patients were from five occupational health care centers. Control subjects were recruited from a university. Determination of the best predictors between CLBP and SLBP patients and between CLBP and SLBP patients and non-patients was made by a forward stepwise logistic model. A total of 157 subjects were included in the study. Of all the clinical tests, several tests in each category had high odds ratio, differentiating CLBP patients from controls. Only a few tests differentiated between CLBP and SLBP patients. The only clinical differences between SLBP patients and controls were in the mobility test and in one test of muscle tightness. The best predictor for CLBP was the lumbar spine flexion test. SLBP patients seemed to differ from the control group in lumbar flexion, in a specific anterior-posterior mobility test, and in tightness of hip flexor muscles. CLBP patients differed from SLBP patients in functional tests, in the presence of sensation in the feet, and in different pain provocation tests. Whether these tests are sufficiently sensitive to classify a more specific diagnostic or clinical subgroup remains untested, and further studies with clinical tests to differentiate among pathological conditions are necessary.