BACKGROUND People prescribed clozapine for treatment-resistant schizophrenia have mandatory haematological monitoring through a case register for identifying reversible neutropenia.
AIMS To quantify risk factors for agranulocytosis in subjects receiving clozapine.
METHOD Data from 12,760 subjects registered to receive clozapine from January 1990 to April 1997 were analysed. Risk factors for agranulocytosis were quantified using a Cox proportional-hazards regression analysis.
RESULTS The risk for agranulocytosis in Asian subjects was 2.4 times that in Caucasians (P = 0.03). There was an age-related increase in risk of 53% per decade (P = 0.0001).
CONCLUSIONS The case register yielded valuable information for guiding research into the causes of the haematological reactions.