Modifying the clinical case definition of pertussis increases the sensitivity of diagnosis in children suspected of Bordetella pertussis infection

Abstract

Background: The WHO defines a surveillance clinical case of pertussis as one with a cough of at least 14 days duration and one of paroxysms, post-tussive vomiting or an inspiratory whoop. Laboratory confirmation is not essential for notification and remains unavailable in most of the developing world where current notification trends suggest that cases are being missed. We aimed to determine the sensitivity and specificity of changing the WHO’s clinical case definition in a cohort of children suspected of Bordetella pertussis infection. MethodsM 95% CI 1.5 – 3.3). Only 23/75 confirmed cases (31%) fulfilled the clinical case definition. The proportion of confirmed infections fulfilling case definition increased to 55% (41/75) when apnoea was added to theWHO definition. The sensitivity increased to 84% (58/75) when duration of cough was omitted from the definition. The specificity however declined from 88% to 56% with this modification. Conclusion: Modifying the WHO case definition of pertussis increases the sensitivity of pertussis clinical case detection. There is an urgent need to adopt a revised clinical case definition that takes into account the “atypical” clinical presentation in young and partially immunized children as well as limited access to laboratory diagnosis.