infectious diseases
Pertussis
Diagnosis of Pertussis
Nasopharyngeal cultures, direct fluorescent antibody testing, and polymerase chain reaction (PCR) testing Serologic testing The catarrhal stage is often difficult to distinguish from Acute Bronchitis or Cultures of nasopharyngeal specimens are positive forB. pertussisin 80 to 90% of cases in the catarrhal and early paroxysmal stages. Because special media and prolonged incubation are required, the laboratory should be notified that pertussis is suspected. Specific fluorescent antibody testing of nasopharyngeal smears accurately diagnoses pertussis but is not as sensitive as culture. Paired acute and convalescent serologic testing may be helpful. PCR testing of nasopharyngeal samples is the most sensitive and preferred test. The white blood cell count is usually between 15,000 and 20,000/mcL (15 and 20 × 109/L) but may be normal or as high as 60,000/mcL (60 × 109/L), usually with 60 to 80% small lymphocytes. Parapertussis is differentiated by culture or the fluorescent antibody technique. 