A Cochrane review included 19 studies with a total of 8 224 subjects; 16 cohort studies (median n=126, range 71 to 2504) and 3 case control studies (38 to100 cases). Only one study was carried out in a primary care population. The reference standards used were: surgical findings in 9 studies, CT or MRI in 6 studies, and surgery and clinical follow-up depending on the severity of symptoms in 1 study. Two of the 3 case-control designs used surgery to confirm disc herniation in cases, and imaging techniques to exclude nerve root compression in controls. The third case control study used MRI in all patients, but used different sets of selection criteria to identify patients with bulging or herniated discs and controls with normal MRI findings.
When used in isolation, diagnostic performance of most physical tests (scoliosis, paresis or muscle weakness, muscle wasting, impaired reflexes, sensory deficits) was poor. Some tests (forward flexion, hyper-extension test, and slump test) performed slightly better, but the number of studies was small. In the one primary care study, most tests showed higher specificity and lower sensitivity compared to other settings. Most studies assessed the Straight Leg Raising (SLR) test. In surgical populations, characterized by a high prevalence of disc herniation (58% to 98%), the SLR showed high sensitivity (pooled estimate 0.92, 95% CI 0.87 to 0.95) with widely varying specificity (0.10 to 1.00, pooled estimate 0.28, 95% CI 0.18 to 0.40). Results of studies using imaging showed more heterogeneity and poorer sensitivity. The crossed SLR showed high specificity (pooled estimate 0.90, 95% CI 0.85 to 0.94) with consistently low sensitivity (pooled estimate 0.28, 95% CI 0.22 to 0.35). Combining positive test results increased the specificity of physical tests, but few studies presented data on test combinations.