Association of clinical characteristics of patients presenting with influenza like illness or severe acute respiratory illness with development of acute respiratory distress syndrome

Clinical judgement and suspicion of influenza based on signs and symptoms of influenza-like illness and severe acute respiratory illness are critical for better patient outcome. Whether clinical characteristics of patients are associated with the development of acute respiratory distress syndrome and PCR positivity of samples was the aim of this study. We included all patients (n=37) presenting with influenza like illness (ILI) or severe acute respiratory illness (SARI) to a tertiary care hospital in northwest Pakistan during December 2015 until the end of January 2016. Each patient was assessed for signs and symptoms, clinical features, treatment, complications and outcome of ILI and SARI. Throat or nasopharyngeal swabs were obtained from 36 patient and analyzed for the presence of Influenza virus by quantitative PCR. Patients presenting with ILI or SARI were febrile (p<0.001, one sample t-test), significantly tachypneic (p<0.001) and had critically lower oxygen saturation (p<0.001). Nasal congestion at presentation (p=0.006, chi-square test for association) and infiltrates on chest radiographs (p=0.025) were significantly associated with acute respiratory distress syndrome. Likelihood of the occurrence of ARDS was significantly increased with decrease in oxygen saturation (Odds ratio; 0.75, 95% CI; 0.46, 1.21, p=0.048) and marginally significantly increased in lower age (Odds ratio; 0.82, 95% CI; 0.58, 1.15, p=0.055) and higher white cell count (Odds ratio; 1.001, 95% CI; 0.99, 1.002, p=0.054). The presence of Influenza type A/H1N1pdm09 strains was confirmed in 7/11 patients. However no significant difference was observed in the clinical features and complications of PCR positive and negative patients. Clinical signs and symptoms of influenza-like illness or severe acute respiratory illness significantly predict the development of complications irrespective of the positivity or negativity of laboratory qPCR reports.