INTEROBSERVER AND INTRAOBSERVER VARIABILITY IN INTERPRETATION OF LUMBAR DISC ABNORMALITIES - A COMPARISON OF 2 NOMENCLATURES

Study Design. A double-blind prospective study was used to measure int erobserver and intraobserver variability when interpreting lumbar spin e magnetic resonance imaging studies of disc abnormalities. Objectives . To evaluate reader consistency when interpreting disc extension beyo nd the interspace, and assess the effect of two distinct nomenclatures on reader consistency. Summary of Background Data. Interobserver and intraobserver variability in interpretation of lumbar disc abnormaliti es is an important consideration in analyzing the technical efficacy o f an imaging modality. However, this has not been well measured (parti cularly for standardized nomenclature). Methods. Magnetic resonance im aging studies of the lumbar spine performed prospectively in 98 asympt omatic volunteers, and an additional 27 selected studies from symptoma tic patients, were read blindly by two experienced neuroradiologists, using two separate nomenclatures. Only the discs were evaluated (625 i nterspaces). Nomenclature I was normal, bulge, herniation. Nomenclatur e II was normal, bulge, protrusion, extrusion. Intraobserver and inter observer variation, were measured with Kappa statistic analysis. Resul ts. Interobserver agreement was 80% for both nomenclatures with a Kapp a statistic of 0.58. Intraobserver agreement was 86% for each reader, with a Kappa statistic of 0.71 and 0.69, respectively. The most common disagreement was for normal versus bulge. The next most common disagr eement (5-6%) was for bulge versus herniation (or protrusion in Nomenc lature II). Herniation was read in 23% of the asymptomatic subjects. U sing Nomenclature II, protrusion was seen in 27% of these subjects. Ex trusion was read in only two asymptomatic subjects.Conclusions. Experi enced readers using standardized nomenclature showed moderate to subst antial agreement when interpreting disc extension beyond the interspac e on magnetic resonance imaging.