Validity of the straight-leg raise test for patients with sciatic pain with or without lumbar pain using magnetic resonance imaging results as a reference standard.

Objective: The aim of this retrospective study was to assess validity of the straight-leg raise (SLR) test using magnetic resonance imaging (MRI) results as a reference standard in a group of patients with L4-L5 and L5-S1 lumbar-herniated disks and sciatic pain. The relationship between diagnostic accuracy of this test, age classes, and grade of lumbar disk displacement was investigated.
Methods: The charts of 2352 patients with sciatic pain with/without lumbar pain were examined. Results of the SLR were then compared with previous spinal MRI. A 2 × 2 contingency table was created, and analysis of sensitivity, specificity, positive and negative predictive values, diagnostic odds ratio, likelihood ratio (LR), and receiver operating characteristic (ROC) curve was carried out. Homogeneous age classes were created to compare them statistically.
Results: Magnetic resonance imaging findings showed lumbar disk herniation (LDH) in 1305 patients. Of these subjects, 741 were positive on SLR testing. Sensitivity was 0.36, whereas specificity was 0.74. Positive and negative predictive values were 0.69 and 0.52, respectively. Positive LR was 1.38, and negative LR was 0.87. Diagnostic odds ratio was 1.59, and ROC analysis showed an area under the curve (AUC) of 0.596. The AUC decreased from 0.730 in the 16- to 25-year subgroup to 0.515 in the 76- to 85-year subgroup. Similar results were obtained in subjects with LDH and nerve root compression.
Conclusions: Our results indicate low accuracy of the SLR in diagnosis of LDH if compared with MRI results. The discriminative power of the SLR seemed to decrease as age increased; thus, positive and negative results may be less conclusive in older patients.
(Copyright © 2011 National University of Health Sciences. Published by Mosby, Inc. All rights reserved.)