Study Design
Retrospective review of MRI images.
Objective
Examine the diagnostic accuracy, discriminative ability, and reliability of the Sedimentation Sign in a sample of patients with clinically diagnosed lumbar spinal stenosis (LSS), low back pain (LBP), vascular claudication, and in asymptomatic controls.
Summary of Background Data
The Nerve Root Sedimentation Sign (SedSign) was recently described as a new diagnostic test for LSS; however the degree to which this Sign is sensitive and specific in diagnosis of LSS is unknown.
Methods
All LSS images were from subjects who had clinically diagnosed LSS confirmed on imaging by a spine specialist. The other images were from people with LBP but no LSS, people with severe vascular claudication, and asymptomatic participants. Three blinded raters independently assessed the images.. A positive Sign was defined as the absence of nerve root sedimentation at the level above or below the level of maximum stenosis.
Results
Images from 148 subjects were reviewed (67 LSS, 31 LBP, 4 vascular, and 46 asymptomatic). Intra-rater reliability for the Sign ranged from kappa = 0.87 to 0.97, and inter-rater reliability from 0.62 to 0.69. Sensitivity ranged from 42–66%, and specificity from 49–78%. Sensitivity improved to a range of 60–96% when only images with a smallest cross sectional area of the dural sac <80mm2 were included. The Sign was able to differentiate (p=0.004) between LSS and asymptomatic controls, but not between LSS and LBP, or between LSS and vascular claudication.
Conclusion
The SedSign was shown to have high intra-rater reliability and acceptable inter-rater reliability. The Sign appears most sensitive in defining severe LSS cases, yet may not aid in the differential diagnosis of LSS from LBP or vascular claudication, or add any specific diagnostic information beyond the traditional history, physical examination and imaging studies that are standard in LSS diagnosis.