ASSOCIATION OF SEROPOSITIVITY FOR HEPATITIS VIRUSES AND APLASTIC-ANEMIA IN THAILAND

Aplastic anemia is more common in the Orient than in western countries , with an incidence in Thailand that is 2- to 3-fold higher than in Eu rope, Aplastic anemia after hepatitis is a well characterized clinical entity, and clinical hepatitis is also prevalent in the Far East. We performed a prospective case control study to determine risk factors f or aplastic anemia in Bangkok and two rural regions during 1989 to 199 4, A total of 375 cases were identified, along with 1,174 hospital con trols matched for age and sex, Historical data were collected by train ed interviewers, Sera from a subset of cases (N = 177) and controls (N = 183) were tested for antibodies to hepatitis viruses A, B, and C an d hepatitis B surface antigen. There was no evidence of association of aplastic anemia with hepatitis B or hepatitis C. Previous exposure to hepatitis A, as determined by immunoglobulin G (IgG) seropositivity, was significantly associated with aplastic anemia: the relative risk a djusted for confounding was 2.9 (95% confidence interval 1.2-6.7), The same association also existed for persons under age 25 years, in whom the prevalence of hepatitis A IgG was lower than in the total populat ion, However, no patients showed evidence of recent infection with hep atitis A (immunoglobulin M [IgM] seropositivity), These results indica te that exposure to a hepatitis virus is a risk indicator for aplastic anemia in Thailand, and while itself unlikely to be etiologic, hepati tis A may be a surrogate marker for another enteric microbial agent.