The accuracy of the clinical diagnosis of Parkinson disease. The HUNT study

Diagnostic accuracy is crucial not only for prognostic and therapeutic reasons, but also for epidemiologic studies. We aimed to study the accuracy of the clinical diagnosis of Parkinson disease (PD) for participants in The Nord-Trøndelag Health Study (HUNT), a health survey, containing data from approximately 126,000 individuals and biological material from 80,000 individuals. We included 980 participants from the HUNT study diagnosed with PD or secondary parkinsonism/related parkinsonian disorders. The participants had been diagnosed in conjunction with admission to hospitals in Trøndelag or through out-patient examination. We validated the diagnosis of PD by reviewing available Electronic Health Records (EHRs) using the MDS Clinical Diagnostic Criteria as gold standard. In total 61% (601/980) of the participants had available EHRs and were selected for validation. Out of those, 92% (550/601) had been diagnosed with PD while 8% (51/601) had been diagnosed with secondary parkinsonism/related parkinsonian disorders. The main outcome measure was the accuracy of the clinical diagnosis of PD for participants in the HUNT study. We verified PD in 65% (358/550) and excluded PD in 35% (192/550) of the participants. According to our results, the overall quality of the clinical diagnosis of PD for participants in the HUNT study is not optimal. Quality assurance of ICD codes entered into health registers is crucial before biological material obtained from these populations can be used in the search of new biomarkers for PD.