A. Alvarezrequejo et al., UNDER-REPORTING OF ADVERSE DRUG-REACTIONS - ESTIMATE BASED ON A SPONTANEOUS REPORTING SCHEME AND A SENTINEL SYSTEM, European Journal of Clinical Pharmacology, 54(6), 1998, pp. 483-488
Objective: Spontaneous reporting is the most common method used in pha
rmacovigilance and the best one to generate signals on new or rare adv
erse drug reactions (ADRs). Under-reporting is a major drawback of thi
s system. The objective of this study was to quantify the extent of un
der-reporting in general practice and to assess the factors which infl
uence it. Method's: Details of ADRs collected through a short intensiv
e survey were compared with primary care spontaneous reports received
by the Castilla y Leon Regional Pharmacovigilance Centre during a 12-m
onth reference period. The survey was undertaken by a random sample of
146 general practitioners (GPs), providing care to 149487 people. The
pharmacovigilance centre received reports concerning the whole region
al population (2.5 million) covered by primary health care. The under-
reporting coefficient (U) was estimated as the ratio between the numbe
r of effects observed by physicians in the survey and those spontaneou
sly reported to the pharmacovigilance centre. Results: The overall und
er-reporting rate was 1144 [95% confidence interval (CI): 928-1409]. U
nder-reporting was greater for psychiatric (2119; 945-4752) and gastro
intestinal (1946; 1424-2659) disorders. Severe effects were more repor
ted (U = 605; 151-2431) than moderate (863; 473-1575) and mild (1209;
973-1503) ones. The under-reporting rate was lower for drugs recently
marketed (706; 406-1230) and slightly lower for unlabelled effects (10
31; 641-1657). Conclusion: The under-reporting rate of ADRs is conside
rable, though not homogeneous for the different cases. This should be
taken into account when comparing adverse effects (AEs) for different
drugs. Underreporting seems to be positively selective, as it involves
mainly the less severe and better-known effects, preserving the value
of spontaneous reporting for signal detection.