Reported exposure to chickenpox: a predictor of positive anti-varicella-zoster antibodies in parturient women.

OBJECTIVE

To determine the positive and negative predictive values of recalled exposure to chickenpox for identifying anti-varicella-zoster virus (VZV) seropositive parturient women.

METHODS

Blood samples were taken from laboring women during February 1998: All women completed questionnaires concerning a history of chickenpox in themselves and their children. Anti-VZV antibodies were determined by the immunofluorescent antibodies to membrane antigen (IFAMA) technique.

RESULTS

Three hundred and twenty-seven women formed the study population; 239 women (73.1%) recalled chickenpox in themselves or their children, of which 229 (95.8%) were seropositive for anti-VZV antibodies. Of the 88 women who gave a negative/uncertain history of chickenpox 82 (93.2%) were seropositive and 6 (6.8%) were seronegative. All 87 mothers who were certain their children had had chickenpox were seropositive, including all 16 mothers who had a negative personal history. Thus, a woman with a history of chickenpox had a positive predictive value of 95.8%, and a woman with a lack of history had a negative predictive value of 6.8% (sensitivity 73.6%, specificity 37.5%), while a positive history of chickenpox in a child had a positive predictive value of 100%.

CONCLUSIONS

Most women with no known history of VZV infection have evidence of prior exposure by serologic testing. Moreover, 100% of women with a negative history who were exposed to VZV in their children were protected from the disease. Therefore, mothers exposed to VZV during pregnancy can be reassured that most likely they are protected. However, the practice of testing all pregnant women exposed to the disease should be continued.