Characteristics of seropositive and seronegative study participants.

aUnadjusted results based on exact Pearson chi-square tests.bAdjusted results based on logistic regression, adjusted for gender and age as a quadratic function. Note that gender is adjusted for age as a quadratic function only. See text for explanation of age adjustment.cData missing for 18 seropositive and 8 seronegative patients.dData missing for 38 seropositive and 21 seronegative patients.eData missing for 29 seropositive and 8 seronegative patients.fData missing for 22 seropositive and 29 seronegative patients.