Objective: To determine the time frame to the diagnosis of clinically established Parkinson’s disease (PD) or atypical parkinsonism after an acute levodopa challenge (LDC) for diagnostic purposes in the real-world clinical setting

Background: The use of clinical diagnostic criteria (UKPDSBB and MDS Clinical Diagnostic Criteria) improves the accuracy of a clinical diagnosis of PD. Time frames of three, five, and even ten years are proposed in those criteria to reach the diagnosis of clinically established PD. However, these time frames were not always based on demonstrated research evidence.

Method: Patients with recent onset of parkinsonism that underwent LDC for clinical prediction of sustained long-term dopaminergic response were identified. Patients fulfilling the UKPDSBB and MDS criteria for PD diagnosis as well as the established diagnostic criteria of other causes of parkinsonism were included. The main outcome of this study was time to a firm, final clinical diagnosis of patients initially presenting with parkinsonism. The cumulative proportion of diagnoses made over time was modeled by the Kaplan Meier technique. Mean time to diagnosis was calculated for patients with a positive or negative response (i.e. change > or < 25%) to levodopa during LCD.

Results: Data from 326 patients were available after excluding uncertain cases due to lack of follow-up or absence of detailed information in medical records. In the first 6 months after the LDC, a final diagnosis could be reached in 77.5±2.5% of patients. The time elapsed to reach 95%, 98%, and 100% of clinical diagnosis certainty were 33, 50, and 108 months, respectively. Time to diagnosis was not different between patients with a final clinical diagnosis of PD compared to those with atypical parkinsonism (10.1±2.1 months vs. 7.4±0.7 months, p=0.10) and clinical diagnosis was lower in patients with a positive response to LDC compared to those with a negative one (5.0±0.9 months vs. 10.2±1.0 months, p<0.01).

Conclusion: In the clinical setting, a clinical diagnosis of PD or atypical parkinsonism could be reached in most of the patients during the first 3 years after performing an LDC, which makes a 5-year follow-up period, as currently proposed for some points of the MDS and UKPDSBB criteria, more than acceptable for an accurate diagnosis of clinically established PD or atypical parkinsonism.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/time-to-diagnosis-of-clinically-established-parkinsons-disease-or-atypical-parkinsonism-is-a-5-year-follow-up-period-necessary/