ABSTRACT
Objectives: Aresurgence of pertussis or whooping cough has been observed worldwide despite broad vaccination coverage. Pertussis like illness [PLI] refers to a clinical syndrome compatible with pertussis infection but lacking laboratory confirmation or an epidemiological link to a confirmed case. Our study aimed to estimate the contribution of Bordetella pertussis infection and identifying predictors of its diagnosis in a cohort of children with PLI
Methods: Demographic and clinical information were retrospectively collected from the medical records of children < 13 years old and hospitalized for PLI in two pediatric units in Oman from 1 January 2012 to 31 December 2013. The laboratory data of all cases were reviewed and confirmed cases of pertussis were identified, analyzed, and compared with non-confirmed cases
Results: A total of 131 patients were enrolled in this study. The majority [95.4% [125/131]] were infants. Only 54.1% [71/131] of admitted children with PLI were tested for pertussis. The incidence of pertussis infection among the tested group was 16.9% [12/71] with a 95% confidence interval 8.2?25.6. Severe illness occurred in 56.4% [74/131] of patients, and six were confirmed to have pertussis. Pediatric intensive care unit admission was required for one confirmed case of pertussis and eight cases from the PLI group [three were negative for pertussis, and five were not tested]. Receiver operator characteristic curve analysis revealed that a white blood cell count >/= 23.5 × 10[9]/L had 96.6% specificity and lymphocytes >/= 17 × 10[9]/L had 98.3% specificity
Conclusions: Taking into consideration that the number tested for pertussis was limited, the incidence of pertussis was 16.9% [12 out of 71 patients]. Lymphocytosis can be used as a reliable predictor for the diagnosis of pertussis especially in the absence of specific confirmatory tests or until their results are available