Administrative database code accuracy did not vary notably with changes in disease prevalence.

OBJECTIVES: Previous mathematical analyses of diagnostic tests based on the categorization of a continuous measure have found that test sensitivity and specificity varies significantly by disease prevalence. This study determined if the accuracy of diagnostic codes varied by disease prevalence.

STUDY DESIGN AND SETTING: We used data from two previous studies in which the true status of renal disease and primary subarachnoid hemorrhage, respectively, had been determined. In multiple stratified random samples from the two previous studies having varying disease prevalence, we measured the accuracy of diagnostic codes for each disease using sensitivity, specificity, and positive and negative predictive value.

RESULTS: Diagnostic code sensitivity and specificity did not change notably within clinically sensible disease prevalence. In contrast, positive and negative predictive values changed significantly with disease prevalence.

CONCLUSION: Disease prevalence had no important influence on the sensitivity and specificity of diagnostic codes in administrative databases.