Prevalence, diagnosis, and disease course of pertussis in adults with acute cough: a prospective, observational study in primary care

BACKGROUND: Most cases of adult pertussis probably remain undiagnosed. AIM: To explore the prevalence, diagnosis, and disease course of acute pertussis infection in adult patients presenting with acute cough. DESIGN AND SETTING: Prospective observational study between 2007 and 2010 in primary care in 12 European countries. METHOD: Adults presenting with acute cough (duration of ≤28 days) were included. Bordetella pertussis infection was determined by polymerase chain reaction (from nasopharyngeal flocked swabs and sputa) and by measurement of immunoglobulin G antibodies to pertussis toxin (PT) in venous blood at day 28. An antibody titre to PT of ≥125 IU/ml or PCR positive result in a respiratory sample defined recent infection. Patients completed a symptom diary for 28 days. RESULTS: Serum and/or respiratory samples were obtained in 3074 patients. Three per cent (93/3074) had recent B. pertussis infection. Prior cough duration >2 weeks discriminated to some extent between those with and without pertussis (adjusted odds ratio 1.89, 95% confidence interval = 1.17 to 3.07; P = 0.010). Median cough duration after presentation was 17 and 12 days in patients with and without pertussis, respectively (P = 0.008). Patients with pertussis had longer duration of phlegm production (P = 0.010), shortness of breath (P = 0.037), disturbed sleep (P = 0.013) and interference with normal activities or work (P = 0.033) after presentation. CONCLUSION: Pertussis infection plays a limited role among adults presenting with acute cough in primary care, but GPs should acknowledge the possibility of pertussis in uncomplicated lower respiratory tract infection. As in children, pertussis also causes prolonged symptoms in adults. However, pertussis is difficult to discern from other acute cough syndromes in adults at first presentation.