Clinical and Laboratory Factors Associated with Pneumonic Infiltrations on Chest Radiography Among Influenza A (H1N1) Infected Patients

ABSTRACT

PURPOSE: Pulmonary complications are the leading cause of death among patients with influenza A (H1N1) infection. Knowledge of factors associated with development of pneumonia among patients infected with influenza A (H1N1) is limited. We conducted a comparative analysis of clinical features and laboratory findings between patients with influenza A (H1N1) infection with and without infiltrations on chest radiography. METHODS: Among adults patients with influenza A (H1N1) infection confirmed by real time reverse transcriptase polymerase chain reaction (rRT-PCR), those who underwent blood tests and chest radiograph at the same time from August to December of 2009 were included in the study. A total of 141 confirmed adult patients with influenza A (H1N1) infection were finally included and were allocated to either the positive infiltration group or the negative infiltration group, as shown on chest radiography. RESULTS: Regarding clinical features, significant differences in pulse rate, respiration rate, and presence of dyspnea were observed between patients with infiltrations on chest radiography and those without infiltrations on chest radiography. According to laboratory findings, differences in leukocytosis, as well as levels of blood urea nitrogen (BUN), alanine amino transferase (ALT), actate dehydrogenase (LDH), and C-reactive protein (CRP) were observed between the two groups. As a result of multivariable analysis, dyspnea and CRP were found to be significant independent factors in association with infiltrations on chest radiography. Best cut-off value of CRP was 2.53 mg/dL with a sensitivity of 78.6% and a specificity of 73.9% (AUC 0.830, p 2.53 mg/dL with infiltrations suggestive of pneumonia on chest radiography was observed in adult patients with influenza A (H1N1) infection.