Impact of <i>ICD-9</i> to <i>ICD-10</i> Coding Transition on Prevalence Trends in Neurology
Ali G. Hamedani, Leah J. Blank, Dylan Thibault, Allison W. Willis
Abstract
OBJECTIVE: ) coding transition on the point prevalence and longitudinal trends of 16 neurologic diagnoses. METHODS: codes for October 1, 2015-December 31, 2017. We compared the prevalence of each diagnosis before vs after the ICD coding transition using logistic regression and used interrupted time series regression to model the longitudinal change in disease prevalence across time. RESULTS: . Six of 16 neurologic diagnoses (37.5%) experienced significant changes in cross-sectional prevalence during the coding transition, most notably for status epilepticus (odds ratio 0.30, 99.7% CI: 0.26-0.34). CONCLUSIONS: coding affects prevalence estimates for status epilepticus and other neurologic disorders, a potential source of bias for future longitudinal neurologic studies. Studies should limit to 1 coding system or use interrupted time series models to adjust for changes in coding patterns until new neurology-specific ICD-9 to ICD-10 conversion maps can be developed.