The validity of a clinical test for the diagnosis of lumbar spinal stenosis

• Spinal stenosis is likely to be more commonly encountered in clinical practice.
• The validity of a simple clinical test was compared to diagnosis by MRI.
• The test had a reasonable sensitivity of 92%, but a poor specificity of 40%.
• The test may be useful to rule out a diagnosis with a negative test result.

BackgroundThe diagnosis and management of acquired lumbar spinal stenosis (ALSS) is an area of growing interest with an increase in its prevalence and detection in the older population.ObjectivesTo investigate the diagnostic accuracy of a modified extension test (MExT) for diagnosing ALSS in subjects aged fifty or over.MethodsSymptomatic response of the bi-component MExT was evaluated and compared against magnetic resonance imaging (MRI) findings in 30 subjects. Estimates of sensitivity, specificity, likelihood ratios (LRs) and post-test probabilities were all calculated, and the capability of the test to discriminate between grade and location of stenosis was also appraised.ResultsMExT sensitivity was high at 92% (95% confidence intervals (CI), 72–99%) leading to a significant negative likelihood ratio at −LR 0.2 (95% CI, 0.03–1.36); conversely, specificity was low at 40% (95% CI, 7–82%) with only a small positive likelihood ratio of +LR 1.53 (95% CI, 0.74–3.16). All correlations between the MExT and concurrent grade, or location of stenosis appeared weak and insignificant.ConclusionsThe MExT was found to demonstrate acceptable criterion validity in relation to ruling-out a diagnosis when a negative result was observed; however, further validation appears warranted.