Do Parkinson's disease patients disclose their adverse events spontaneously?

Background: Underreporting of adverse drug reactions is common but has been rarely studied in Parkinson's disease (PD).

Objective: To compare the prevalence of adverse events (AEs) in relation to antiparkinsonian drugs in PD patients using two different data collection methods: patient's spontaneous reporting versus a predefined investigator-driven structured interview. Secondary objectives were to assess factors related to spontaneous reporting and to compare the rate of AE reporting in PD patients with that of a group of non-parkinsonian post-stroke patients.

Study Design: Cross-sectional study.

Patients: Ambulatory, cognitively intact PD or post-stroke outpatients.

Interventions: None.

Outcome Measures: Patients were first asked by means of an an open question to disclose any unpleasant effects in connection with their current medications that had occurred during the previous week. Afterwards, a predefined questionnaire listing the most common AEs known to be related to antiparkinsonian drugs was used to question the same patients in a systematic manner about the presence of any AE during the same week. Chronological and semiological criteria were used to classify the reported AEs as "unrelated" or "possibly/plausibly related" to the antiparkinsonian treatment.

Results: A total of 203 PD and 52 post-stroke patients of comparable age and sex were recruited. Eighty-five PD and five post-stroke patients reported spontaneously at least one AE (42 vs. 10%, p < 0.01), while 203 PD and 47 post-stroke patients reported at least one AE following the structured questionnaire (100 vs. 90%, p < 0.001). In PD patients, there were a total of 112 spontaneously reported AEs as compared with 1,574 according to the structured questionnaire (7%). Spontaneous disclosure of AEs was associated with experiencing >2 AEs [OR = 1.2 (1.1-3.2)], logistic regression). Seventy-four percent of PD patients had ≥1 AE possibly/plausibly related to antiparkinsonian drugs.

Conclusions: Results showed that only 7% of AEs were reported spontaneously by patients, thus underscoring the importance of systematically asking about AEs in PD patients.