Evaluation of the diagnostic utility of the new clinical case definition of pertussis - experience from sentinel and hospital-based pertussis surveillance

Abstract

Introduction/Objective. Global surveillance systems use different clinical case definitions of pertussis. The aim of this study was to identify sign and symptom combinations with best relation with laboratory confirmed pertussis. Methods. A one-year prospective observational study, proposed by the Global Pertussis Initiative (GPI) for three age groups (0–3 months, four months to nine years, and ≥ 10 years) was performed in Novi Sad to evaluate the performance of the clinical case definition of pertussis. Laboratory confirmation of B. pertussis infection was obtained using the DNA polymerase chain reaction (PCR) or ELISA serology tests. Results. From October 1, 2013 to September 30, 2014, 103 (32.3%) out of 319 participants with suspected pertussis had laboratory-confirmed pertussis. Combined whooping, post-tussive emesis, and worsening of symptoms at night was the best predictor of pertussis in outpatients aged four months to nine years (positive likelihood ratio (LR+) 11.6), while among inpatients of the same age group it was apnoea (LR+ 13.5). The LR+ in outpatients aged ≥10 years for combinations of apnoea and post-tussive emesis, or a combination of whooping and sweating episodes between paroxysms and post-tussive emesis was 16.8, while among in-patients LR+ was < 2.3 for all combinations in the same age group. Conclusions. The GPI case definitions for pertussis are good predictors for laboratory-confirmed pertussis and are useful for the purpose of pertussis surveillance.

Keywords

• pertussis (whooping cough)
• Global Pertussis Initiative
• case definition
• surveillance