Distribution of positive and negative cases with laboratory-confirmed pertussis for participants ≥7 years olda

Method of diagnosis (cutoff)No. of casesNo. of noncases
Positive pertussis test
    ptxA-Pr PCR133
    IS481 PCR3717
    Single serology (≥125 EU/ml)539
    Paired serology (×4b)1312
Positive pertussis test using combination of single serology (≥125 EU/ml) with:
    Paired serology (×4)6612
    PtxA-Pr PCR6212
    IS481 PCR7323
  • a Subjects were contacts of infant pertussis cases with complete laboratory data (n = 195). Complete data include symptoms, serology, and PCR (IS481 and ptx-Pr) at enrollment and symptoms and serology at follow-up visit 1 month later.

  • b ×4, fourfold change in titer.

  • cCase definition: laboratory-confirmed symptomatic contact. There were 82 cases and 113 noncases.