Post-viral parenchymal lung disease of COVID-19 and viral pneumonitis: A systematic review and meta-analysis.

BackgroundApproximately half of patients discharged following COVID-19 related hospitalisation are reported to suffer from persisting respiratory symptoms. We assess the prevalence of long term radiological and functional pulmonary sequelae in survivors from COVID-19 and other viral pneumonia in published literature. MethodsWe performed systematic review and meta-analysis of all original studies in adults admitted to hospital with SARS-CoV-2, SARS-CoV, MERS-CoV, or Influenza pneumonia and followed within 12 months from discharge. Searches were run on MEDLINE and Embase, with the last update on 1st March 2021. Primary outcomes were presence of 1) radiologic sequelae at CT scans; 2) restrictive impairment; 3) reduced diffusing capacity for carbon monoxide (DLCO). This review is registered on PROSPERO, CRD42020183139. ResultsSixty studies were included for qualitative synthesis, of which 41 were suitable for meta-analysis. On follow up CT scans, the overall estimated proportion was 0{middle dot}56 (95%CI 0{middle dot}44 to 0{middle dot}66, I2= 94{middle dot}44%) for inflammatory changes, and 0{middle dot}40 (95%CI 0{middle dot}29 to 0{middle dot}52, I2=95{middle dot}19%) for fibrotic findings. In SARS-CoV-2 specifically, proportions were estimated at 0{middle dot}43 (95%CI 0{middle dot}32 to 0{middle dot}56, I2=94.60%) and 0{middle dot}30 (95%CI 0{middle dot}19 to 0{middle dot}43, I2=94.89%) for inflammatory and fibrotic findings, respectively. Overall proportion for restrictive impairment was 0{middle dot}19 (95%CI 0{middle dot}12 to 0{middle dot}27, I2=94{middle dot}46%), DLCO reduction was estimated at 0{middle dot}45 (95%CI 0{middle dot}38 to 0{middle dot}52, I2=90{middle dot}10). Elevated radiological and functional estimates persisted across follow-up times. Confidence in the estimates was deemed very low as studies were largely observational without control groups, heterogeneity in estimates was high but was not clearly attributable to between-study differences of severity or design. ConclusionAlthough estimates of prevalence are likely limited by differences in case mix and initial severity, a substantial proportion of radiological and functional sequelae are observed following viral pneumonitis, including COVID-19. This highlights the importance of vigilant radiological and functional follow up. FundingNational Institute for Health Research (NIHR)