The test of Lasegue - Systematic review of the accuracy in diagnosing herniated discs

Study Design. A systematic review of the literature including statistical m eta-analysis. Objectives, To evaluate published methods of the test of Lasegue or straigh t leg raising test and the cross straight leg raising test by using a recen tly developed criteria list and to summarize and explore reasons for variat ion in diagnostic accuracy. Summary of Background Data. Little evidence exists on the diagnostic accura cy of the widely used straight leg raising test and the cross straight leg raising test in diagnosing herniated discs in patients with low back pain. Methods. MEDLINE and EMBASE searches up to 1997 showed 17 diagnostic public ations evaluating the straight leg raising test with surgery as reference s tandard. Quality of methods was assessed with a specific checklist. Eleven studies were selected for statistical pooling. Sources of variation and het erogeneity were studied by meta-regression of the diagnostic odds ratio. Results. AII studies were surgical case-series at nonprimary care level. Ve rification-bias was obvious in one study. Pooled sensitivity for straight l eg raising test was 0.91 (95% CI 0.82-0.94), pooled specificity 0.26 (95% C I 0.16-0.38). Pooled diagnostic odds ratio was 3.74 (95% CI 1.2-11.4), Disc riminative power was lower in recent studies, in studies with only inclusio n of primary hernias, and with blind assessment of both the index-test (str aight leg raising test) and the reference (surgery). For the cross straight leg raising test pooled sensitivity was 0.29 (95% CI 0.24-0.34), pooled sp ecificity was 0.88 (95% Cl 0.86-0.90), and the pooled diagnostic odds ratio 4.39 (95% Cl[ 0.74-25.9). Conclusions. The diagnostic accuracy of the straight leg raising test is li mited by its low specificity. Discriminative power decreased with a more va lid design, a more homogenous case-mix, and year of publication. Although t he studies may reflect everyday clinical practice, they do not enable a val id evaluation of the diagnostic accuracy of both tests. Diagnostic research should evaluate the validity of the complete diagnostic process and study the evidence of the added value of the different tests used.