Histopathologic and Immunohistochemical Assessment of Acute Respiratory Distress Syndrome (ARDS): Challenges and Complexities of Postmortem Diagnosis

Acute respiratory distress syndrome (ARDS) is a life-threatening condition due to acute lung injury (ALI), characterized by rapid-onset respiratory failure, leading to the clinical manifestations of poor lung compliance, severe hypoxemia, and dyspnea. ARDS/ALI has many causes, most commonly related to infections (sepsis, pneumonia), traumas, and multiple transfusions. The objective of this study is to assess the performance of postmortem anatomopathological examination in identifying etiological agents associated with ARDS or ALI in deceased patients from the State of São Paulo from 2017 to 2018. A retrospective cross-sectional study was performed based on the final outcome obtained by histopathology, histochemical, and immunohistochemical examination for ARDS/ALI differential diagnosis at the Pathology Center of the Adolfo Lutz Institute in São Paulo, Brazil. Of the 154 patients clinically diagnosed with ARDS or ALI, 57% tested positive for infectious agents, and the most frequent outcome was influenza A/H1N1 virus infection. In 43% of cases, no etiologic agent was identified. The opportunity to establish a diagnosis, identify particular infections, confirm a microbiological diagnosis, and uncover unanticipated etiologies is provided by postmortem pathologic analysis of ARDS. A molecular assessment could improve the diagnosis accuracy and lead to research into host responses and public health measures.