TABLE 2

Frequencies of positive pertussis cases in different age groups by culture and/or RT-PCR and serology (PT-ELISA)

CharacteristicGroup 1 (<1 yr)Group 2 (1–6 yr)Group 3 (≥7 yr)
No. of pertussis-positive cases/total no. of cases101/26031/8194/162
No. (%) of positive cases by culture and/or RT-PCR61 (60.4)a2 (6.4)3 (3.2)
No. (%) of positive cases by PT-ELISA18 (17.8)25 (80.6)81 (86.2)
No. (%) of positive cases by combined assaysb22 (21.8)4 (13)10 (10.6)
No. of seronegative cases1504762
Pc<0.0001<0.0001<0.0001
  • a Percentages were calculated with positive specimens by at least one test.

  • b Combined assays: culture and/or RT-PCR and PT ELISA.

  • c Culture and/or RT-PCR versus PT-ELISA.