TABLE 5.

Comparative sensitivities, specificities, and Youden index for diagnosis of symptomatic laboratory-confirmed pertussisa

Method of diagnosis (cutoff)% Sensitivity (95% CIc)% Specificity (95% CI)Youden index
ptxA-Pr PCR15.5 (10.4-20.6)97.3 (95.0-99.6)0.13
IS481 PCR44.0 (37.0-51.0)84.7 (79.6-89.8)0.29
Single serology (≥100)67.9 (61.3-74.5)90.1 (85.9-94.3)0.58
Paired serology (×2b)23.8 (17.8-29.8)83.8 (78.6-89.0)0.08
Combination of single serology (≥100 EU/ml) with:
    Paired serology (×2)85.7 (80.8-90.6)75.7 (69.7-81.7)0.61
    PtxA Pr PCR77.4 (71.5-83.3)87.4 (82.7-92.1)0.65
    IS481 PCR90.5 (86.4-94.6)77.5 (71.6-83.4)0.68
  • a Subjects are contacts of infant pertussis cases for whom there is complete laboratory data (n = 195). Complete data include symptoms, serology, and PCR analysis (IS481 and ptx-Pr) at enrollment and symptoms and serology at follow-up visit 1 month later.

  • b ×2, twofold change in titer.

  • c CI, confidence interval.