Incidence of agranulocytosis in Southwest France

Background: Updated knowledge of background event rates is fundamental to risk assessment. Objective: To estimate the incidence of agranulocytosis in the general population in Southwest France. Methods: All definite cases of acute non-cancer drug-related agranulocytosis in subjects aged more than 16 years were systematically retrieved weekly from Medical departments or labs in the catchment area (approximately 3.5 millions inhabitants). Event rates were compared to population figures from 1999 census data, and Poisson 95% confidence intervals computed. Results: From January 1st 1997 to December 31st 1998, 87 cases of agranulocytosis were identified, 58 being validated by an independent ad hoc panel of experts. The overall annual incidence rate was 9.2 per million inhabitants (95%CI: 6.9;13.0); 7.7 (95%CI: 4.8; 11.7) per million in men, and 10.5 (95%CI: 7.2; 14.8) per million in women. These rates of all-cause acute agranulocytosis can be used as expected background reference rate for specific risk assessment.