RISK OF AGRANULOCYTOSIS AND APLASTIC-ANEMIA IN RELATION TO HISTORY OFINFECTIOUS-MONONUCLEOSIS - A REPORT FROM THE INTERNATIONAL AGRANULOCYTOSIS AND APLASTIC-ANEMIA STUDY

The general objective of this study was to evaluate the risks of agran ulocytosis and aplastic anemia in relation to drug use. Other potentia l risk factors, including history of infectious mononucleosis, were al so evaluated. In an international population-based case-control study, cases of agranulocytosis and aplastic anemia and controls, who were p atients with selected diagnoses, were identified from the same hospita ls. Information on drug use was obtained in a structured interview. Li mited information on environmental exposures and on selected items of medical history, including infectious mononucleosis, was also recorded . The possible effects of these factors on the risk of the two blood d yscrasias were evaluated. Relative risks were estimated by stratified analysis and by multiple logistic regression. Among 319 cases of argan ulocytosis, 12 patients (4%) gave a history of infectious mononucleosi s at least 1 year previously; among 2180 controls the corresponding nu mber was 11 (0.5%) (multivariate relative risk estimate, 6.2; 95% conf idence interval, 2.3-17). A nonsignificant elevation in the relative r isk was observed for aplastic anemia. The data suggest that infectious mononucleosis may confer a long-term increase in the risk of agranulo cytosis. However, the association was an unexpected one, identified in the course of multiple comparisons, and it must be independently conf irmed.