Consumer reporting of adverse drug reactions: a retrospective analysis of the Danish adverse drug reaction database from 2004 to 2006.

BACKGROUND: Reporting adverse drug reactions (ADRs) has traditionally been the sole province of healthcare professionals. Since 2003 in Denmark, consumers have been able to report ADRs directly to the authorities. The objective of this study was to compare ADRs reported by consumers with ADRs reported from other sources, in terms of their type, seriousness and the suspected medicines involved.
METHODS: The number of ADRs reported to the Danish ADR database from 2004 to 2006 was analysed in terms of category of reporter, seriousness, category of ADRs by system organ class (SOC) and the suspected medicines on level 1 of the anatomical therapeutic chemical (ATC) classification system. ADR reports from consumers were compared with reports from other sources (physicians, pharmacists, lawyers, pharmaceutical companies and other healthcare professionals). Chi-square and odds ratios (ORs) were calculated to investigate the dependence between type of reporter and reported ADRs (classified by ATC or SOC).
FINDINGS: We analysed 6319 ADR reports corresponding to 15 531 ADRs. Consumers reported 11% of the ADRs. Consumers' share of 'serious' ADRs was comparable to that of physicians (approximately 45%) but lower than that of pharmacists and other healthcare professionals. When consumer reports were compared with reports from other sources, consumers were more likely to report ADRs from the following SOCs: 'nervous system disorders' (OR = 1.27; 95% CI 1.05, 1.53); 'psychiatric disorders' (OR = 1.70; 95% CI 1.31, 2.20) and 'reproductive system and breast disorders' (OR = 2.02; 95% CI 1.13, 3.61) than other sources. Compared with other sources, consumers reported fewer ADRs from the SOCs 'blood and lymphatic system disorders' (OR = 0.22; 95% CI 0.08, 0.59) and 'hepatobiliary system disorders' (OR = 0.14; 95% CI 0.04, 0.57). Consumers were more likely to report ADRs from the ATC group N (nervous system) [OR = 2.72; 95% CI 2.34, 3.17], ATC group P (antiparasitic products) [OR = 2.41; 95% CI 1.32, 4.52] and ATC group S (sensory organs) [OR = 4.79; 95% CI 2.04, 11.23] than other sources. Consumers reported fewer ADRs from the ATC group B (blood and blood-forming organs) [OR = 0.04; 95% CI 0.006, 0.32] and the ATC groups J (anti-infective for systemic use) [OR = 0.44; 95% CI 0.33, 0.58], L (antioneoplastic and immunomodulating agents) [OR = 0.19; 95% CI 0.12, 0.30] and V (various) [OR = 0.03; 95% CI 0.004, 0.21] than other sources. In the SOC 'nervous system disorders', consumers reported seven categories of ADRs that were not reported by the other sources.
CONCLUSION: This study showed that compared with other sources, consumers reported different categories of ADRs for different types of medicines. Consumers should be actively included in systematic drug surveillance systems, including clinical settings, and their reports should be taken as seriously as reports from other sources.