ABSTRACT
Background: COVID-19 is a relatively new disease that can progress to ARDS, respiratory failure and death. Identifying specific morphological lung injury in COVID-19 patients, can give a better understanding of subjacent physiopathology.Our aim is to provide a rigorous summary of the evidence available of lung histological findings in COVID-19 patients.Methods:Eligibility criteria: Any quantitative design, reporting raw data of lung histological findings in COVID-19 patients. Reviews, guidelines, other organs’ histological features were excluded.Information sources: The centralized repository L·OVE (Living OVerview of Evidence), PubMed/Medline, Cochrane Central Register of Controlled Trials (CENTRAL), LitCovid, WHO Covid-19 Database, and medRxiv. The search covered the period from January 1, 2020 until April 3, 2021.Risk of bias: was assessed using Joanna Briggs Institute tools, by four observers and consensus.Synthesis of Results: Each and every lung histopathological finding was extracted. Frequencies for each finding were calculated, and then data from the two most frequent findings were pooled by meta-analysis using a Der Simmonian-Liard model with random-effects model. Heterogeneity was measured.Results:Included studies: From 252 references, 69 articles fulfilled inclusion criteria, summarizing 594 subjects.Synthesis of results: Demographic: 381 men, 179 female and 34 not specified. Mean age in case series was 87.57 years (SD+ 1.57), and in case reports 61.85 years (SD + 1.51). Fourteen case series (45.16%), and 21 case reports (55.26%) presented low risk of bias. Meta-analysis of proportions showed DAD in 0.62 (CI 95% 0.51-0.72), I2 59% (p<0.01), in its early phase (85.14%).Discussion: The limitations of the evidence included in the review was a relative selection bias for included subjects. Interpretation: Early DAD was the most frequent histopathological finding in lung samples from severe COVID-19 patients. Registration Details: Study’s registration number PROSPERO CRD4202018936.Funding Information: There was no source of funding.Declaration of Interests: We all declare no conflict of interest.