Studies have shown that cultures are more likely to be positive if the sample is collected during the first stage and early in the second. A negative culture is usually seen after 5 days of treatment with antibiotics. Other laboratory methods used to diagnosis pertussis infection such as serologic testing and PCR are available in certain labs. However, neither method has been shown to be more specific than culture isolation of the organism. A complete blood count may be performed.
Antibiotics are most effective if given early in the first phase of the illness.
Some strains of the illness are resistant to certain antibiotics. Symptoms would get worse if this is the case. In addition to treating the adult or child who has pertussis, everyone in the household should be treated with antibiotics as well. Close contacts younger then 7 years who have completed their primary series but have not received a booster of DTP or DTaP within 3 years of exposure should be given the booster dose. Vaccination in adults is not recommended universally because of the increased vaccine-related side effects seen in adults and because illness related to pertussis decreases with age.