Determining who has pertussis can be difficult. Whenever possible, clinicians should obtain a nasopharyngeal (NP) swab or aspirate from all persons with suspected cases. A properly obtained NP swab or aspirate is essential for optimal results (see Figures 1 & 2).
If culture is planned, directly plate the collected NP swab or immediately place it into transport medium. Laboratory scientists should plate NP swabs and aspirates within 24 hours of collection. The same specimen can be used both for culture and polymerase chain reaction (PCR). With PCR, the most rapid test, ideally collect the specimen during the first 3 weeks of illness. However, PCR may provide accurate results for up to 4 weeks. Culture has better specificity, but takes up to 7 days to obtain results. For culture, clinicians ideally need to collect the specimen during the first 2 weeks of illness.