Parkinson's disease diagnosis codes are insufficiently accurate for electronic health record research and differ by race

Background: There are no evidence-based guidelines for data cleaning of electronic health record (EHR) databases in Parkinson's disease (PD). Previous filtering criteria have primarily used the 9th International Statistical Classification of Diseases and Related Health Problems (ICD) with variable accuracy for true PD cases. Prior studies have not excluded atypical or drug-induced parkinsonism, and little is known about differences in accuracy by race. Objective: To determine if excluding parkinsonism diagnoses improves accuracy of ICD-9 and-10 PD diagnosis codes. Methods: We included & GE;2 instances of an ICD-9 and/or-10 code for PD. We removed any records with at least one code indicating atypical or drug-induced parkinsonism first in all races, and then in Non-Hispanic White and Black patients. We manually reviewed 100 randomly selected charts per group before and after filtering, and performed a test of proportion (null hypothesis 0.5) for confirmed PD. Results: 5633 records had & GE;2 instances of a PD code. 2833 remained after filtering. The rate of true PD cases was low before and after filtering to remove parkinsonism codes (0.55 vs. 0.51, p = 0.84). Accuracy was lowest in Black patients before filtering (0.48, p = 0.69), but filtering had a greater (though modest) impact on accuracy (0.68, p < 0.001). Conclusions: There was inadequate accuracy of PD diagnosis codes in the largest study of ICD-9 and-10 codes. Accuracy was lowest in Black patients but improved the most with removing other parkinsonism codes. This highlights the limitations of using current real-world EHR data in PD research and need for further study.

Automated summary

This study aimed to determine whether excluding diagnoses of peripheral parkinsonism and drug-induced parkinsonism improves the accuracy of ICD-9 and -10 codes for Parkinson's disease. The study found that although accuracy was lowest in Black patients, removing other parkinsonism codes had a significant impact on accuracy. This highlights the limitations of using current real-world electronic health record data in Parkinson's disease research and calls for further study.