Objective: Pandemic H1N1 influenza is the predominant influenza virus circulating in Turkey in 2009. Because of the clinical manifestations of influenza overlap with those attributable to other common respiratory illnesses of childhood, establishing a diagnosis of influenza requires confirmatory testing. The aim of our study was to define the predictive value of rapid influenza antigen detection test in children presenting to a pediatric emergency care department with influenza-like illness and to compare with clinical signs and symptoms.

Methods: From October to November 2009, 3646 patients presented with influenza-like illness to the pediatric emergency department. Influenza-like illness is defined as fever with cough or sore throat in the absence of a known cause other than influenza. Enrollment criteria included fever and at least one of the following symptoms: coryza, cough, headache, sore throat, or myalgia. All 322 enrolled patients received a nasal wash for rapid influenza diagnostic tests, and the results were compared with clinical signs.

Results: Rapid influenza detection test result was found positive in 167 (51.9%) of 322 patients. Clinical findings included fever as the presenting complaint (100%), fever (≥38 °C) (93.4%), cough (91.3%), rhinorrhea (66.1%), sore throat (35.1%), vomiting-diarrhea (22.4%), myalgia (20.2%), headache (18%) and shortness of breath (12.1%). There were 211 patients (65.5%) at high risk for the development of complications of pandemic H1N1 influenza A such as chronic lung disease (asthma) (n = 103, 48.8%), age younger than 2 years (n = 78, 37%), and neurologic disease (n = 10, 4.7%). The positivity rate and sensitivity of the test increase up to 70% in patients, who had the high body temperature (≥39 °C). The rapid test achieved the highest sensitivity in patients, who have high fever (≥39 °C), myalgia, vomiting, and diarrhea.

Conclusions: We found that if the patients have high fever (≥39 °C), myalgia, and vomiting-diarrhea together, the likelihood of rapid antigen test positivity rate increases in patients, who presented with influenza-like illness.