Early diagnosis pathway for laboratory testing in the context of pertussis resurgence

The resurgence of pertussis continues to be a global public health concern, especially in China in recent years. It is critical to identify atypical cases in adolescents and adults and to improve sensitivity to early laboratory diagnosis. The subjects were laboratory-confirmed cases in Chaoyang district between 2018 and 2023, detected through pertussis symptom surveillance, or reported in the National Notifiable Disease Reporting System. Logistic regression and decision tree models were used to examine potential factors influencing laboratory diagnostic sensitivity. Among the 446 laboratory-confirmed cases, the sensitivity of PCR and serological diagnosis of single serums was 83.4% and 49.5%. Logistic regression analysis showed that age and vaccination, disease course at sampling, and years of onset were the factors that affected the sensitivity of laboratory diagnosis (p < .05). The decision tree model indicated that the sensitivity of PCR was highest among unvaccinated and partially vaccinated cases (97.9%), while it was lowest in adults (63.3%); PCR sensitivity in children and adolescents vaccinated with 3-4 doses was 79.1%, and the sensitivity increases to 88.4% at sampling during the first 3 weeks of onset. Serodiagnostic sensitivity was low, especially in unvaccinated cases (4.5%), and higher in adults, children and adolescents receiving booster immunization (63.1%), but decreased to 46.2% at sampling during the first 3 weeks of onset. Because serological diagnostic sensitivity is low and overlaps in positivity with PCR is limited (9.2%), lower cut-off values are recommended to improve diagnostic sensitivity in the early stages of the disease, in adults, in children and adolescents receiving booster immunization.