ABO blood group, secretor state, and susceptibility to recurrent urinary tract infection in women.

ABO blood group and secretor state was determined in 319 women with recurrent urinary tract infection and compared with those of a control group of 334 women of similar age ranges. Women of blood groups B and AB who are non-secretors of blood group substances showed a significant relative risk of recurrent urinary tract infection of 3.12 (95% confidence limits, 1.49 and 6.52) in comparison with other types. This appears to be a genuine example of synergy in which absence of anti-B isohaemagglutinin and secretor substances combines to give an increased risk of recurrent urinary tract infection. Determination of blood group and secretor state may provide additional information in identifying those at risk.