Influence of Verification Bias on the Assessment of MRI in the Diagnosis of Meniscal Tear

OBJECTIVE. Previous studies of the sensitivity and specificity of MRI in the diagnosis of meniscal tear have not included correction for verification bias. The purpose of this study was to investigate the extent to which verification bias affected assessment of the utility of MRI in the diagnosis of meniscal tear. MATERIALS AND METHODS. The patients included in the study were outpatients who from April 2006 through July 2008 consecutively visited a single institution for MRI of the meniscus for evaluation of knee pain. For patients who underwent arthroscopy in addition to MRI, the sensitivity and specificity of MRI were calculated. Global sensitivity analysis of data on patients who did not undergo arthroscopy was performed to estimate the influence of verification bias. Global sensitivity analysis is a method for graphically determining whether a particular pair of sensitivity and specificity estimates is compatible with observed data. RESULTS. Eighty-two patients (23%) underwent arthroscopic verification. The sensitivity and specificity of MRI were 85% and 31%. When the possibility of meniscal tears in patients who did not undergo arthroscopy was subjected to global sensitivity analysis, the sensitivity of MRI ranged from 29% to 95% and the specificity ranged from 3% to 92%. All combinations of sensitivity and specificity produced a butterfly-shaped curve, but the base case was not inside the curve. CONCLUSION. Verification bias greatly affected assessment of the utility of MRI in the diagnosis of meniscal tear. Sensitivity and specificity from previous studies may be incompatible with our data owing to verification bias.