Table 1.
Summary of Definitions of Pertussis Infectiona
| Criteria | Primary Definition | Modified Definition |
| Nasopharyngeal swab PCR positive | ||
| Acute specimen | Positive | NA |
| Convalescent specimen | Positive | Positive |
| Nasopharyngeal aspirate PCR or culture positiveb | Positive | Positive |
| Anti-PT immunoglobulin G titer | ||
| Acute specimen | ≥94 EU/mL | NA |
| Convalescent specimen | ≥94 EU/mL | ≥94 EU/mL |
| Acute to convalescent antibody increase | ≥2-fold | ≥2-fold |
Abbreviations: EU, enzyme-linked immunosorbent assay (ELISA) units per milliliter; NA, not applicable; PCR, polymerase chain reaction; PT, pertussis toxin.
a
The presence of a single criterion within a definition was sufficient to establish the diagnosis of pertussis infection.
b
Nasopharyngeal aspirates were obtained only from subjects who developed fever, cough, runny nose, or sore throat during the postexposure monitoring period.