H1N1 influenza: Characterization of initial chest radiographic findings and prognostic value of serial chest radiographs

Abstract

ObjectiveThe aim of this study was to recognize and characterize the initial chest radiographic findings of H1N1 infection and to evaluate whether serial chest radiographs were useful in assessing the severity of infection and predicting the clinical outcome. Materials and methods27 patients hospitalized for H1N1 infection, from January 2015 to May 2016 were retrospectively evaluated, including 17 (62.9%) female patients and 10 (37.1%) male patients, with age ranging between 2 days and 65 years. Radiographs obtained at the time of admission were reviewed and studied for characteristic imaging patterns, laterality (unilateral or bilateral) and zonal distribution of the opacities. Serial chest radiographs taken were reviewed to look for progression or resolution of the imaging findings and compared with the final outcome. ResultsOf the female patients, 4 (23%) were pregnant and 1 (6%) was in the immediate post-partum period. Of the 27 patients, 25 (92.6%) had abnormal and 2 (7.4%) had normal radiological findings on initial chest radiographic appearance. One patient was lost to follow-up, 16 (62%) of the remaining 26 succumbed to the disease while the remaining 10 (38%) improved. Three of the pregnant patients and the postpartum patient had adverse outcomes. Involvement of greater than 4 lung zones and bilateral involvement indicated a poor prognosis. Abnormal chest radiographic findings included consolidation, peribronchial cuffing, nodular opacities and reticulo-nodular opacities, with the most common being consolidation with or without peribronchial cuffing. Patients with more than 4 zones of involvement invariably had an adverse clinical outcome. ConclusionInitial chest radiographic findings help in diagnosing the type of pneumonia, and consolidation associated with peribronchial cuffing is a common finding in viral pneumonia like H1N1. Prognosis based on evaluation and monitoring of serial chest radiographs is a valuable tool in predicting the final clinical outcome of the patient. Extensive involvement of both lungs, in the form of multi-zonal and bilateral lung opacities is frequently associated with adverse prognosis.