The Proportion of Patient Reports of Suspected ADRs to Signal Detection in the Netherlands: Case-control Study

Aim: To determine the contribution of patients' adverse drug reaction (ADR) reports to signals detection, through a study of the signals sent by Lareb to the Dutch Medicines Evaluation Board.

Methods: The percentage of patient's ADR reports contributing to generate signals of adverse drug reactions was determined. A case-control design was used to study if the proportion of patient reports in associations that had been selected as 'signals' differed from non-signals. A logistic regression analysis was used to calculate the Odds Ratio with 95%CI for patient reports in the cases and controls.

Results: The number of patient reports which contributed to a signal has increased from 0 reports in 2003 to 31 reports in 2008 (9% of total). Since 2005 patient reports have triggered particular associations to be selected as a signal. In 2007, 28% of all trigger reports were reported by a patient. The case-control analysis showed that patient reports were equally present in the reports used in signal formation (cases) as in the controls, reports not contributing to a signal. Odds Ratio (OR) was 1.10 (95%CI 0.81-1.49) and OR = 0.96 (95%CI 0.50-1.87) for the 'trigger reports'.

Conclusions: The proportion of patient reports contributing to generate signals was equal to the proportion of patient reports in the database. Patient's reports of adverse drug reactions can provide a valuable contribution to the detection of signals in addition to healthcare professionals' reports. In the Netherlands, direct patient reports have added to the signals of adverse drug reactions sent to the Medicines Evaluation Board.