[Laboratory diagnosis of pertussis. Role of serology]

Culture is the reference method for the diagnosis of infection by Bordetella pertussis. Nevertheless, delayed sample collection and previous antibiotic treatment can limit culture sensitivity. In principle, direct immunofluorescence provides immediate diagnosis. It is, however, a subjective procedure that shows low sensitivity and specificity. PCR techniques increase culture sensitivity while maintaining high specificity, but their performance decreases along the evolution of the disease. Serologic methods are the main alternative for cases in which diagnosis is delayed. Current recommendations center on ELISA techniques that include purified antigens, such as filamentous hemaglutinin, and particularly, pertussis toxin. Traditionally, serological diagnosis requires confirmation by demonstrated seroconversion, but now the possibility of diagnosis based on titration of a single serum sample is being evaluated.