INTERREADER RELIABILITY FOR A NEW CLASSIFICATION OF LUMBAR-DISK DISEASE

Rationale and Objectives. The nomenclature that divides disk herniatio ns into protrusions and extrusions may increase the specificity of mag netic resonance (MR) imaging for clinically important lesions. Our goa l was to determine this terminology's interreader reliability. Methods . Three readers who were unaware of patients' histories independently read MR images of 34 consecutive patients with back pain. Readers clas sified disks at the lowest three lumbar levels as normal, bulging, pro truded, or extruded. Kappa and weighted kappa values were the primary measures of agreement. Results. Weighted kappa values showed fair-to-m oderate agreement. Kappas for the dichotomous decision of extrusion pr esent or absent were more variable, ranging from 0 to .78. Major disag reements (greater than a single category) occurred with 6.2% of all co mparisons and in 10 of 34 volunteers; five involved extrusions. Conclu sion. Overall, readers achieved moderate agreement for this new nomenc lature. However, agreement for the presence or absence of an extrusion was less reliable.