Bronchoalveolar lavage in suspected COVID-19 cases with a negative nasopharyngeal swab: a retrospective cross-sectional study in a high-impact Northern Italy area.

COVID-19 diagnosis relies on molecular testing for SARS-CoV-2 via nasopharyngeal swab in the presence of suggestive clinical, radiological and laboratory findings. Since bronchoalveolar lavage liquid (BAL) collected during fibrobronchoscopy may increase test sensitivity compared to nasopharyngeal swabs, it was performed during the 2020 pandemic in clinically or radiologically suspected cases. Our aim was to determine whether clinical features, chest computed tomography (CT) findings or laboratory tests may predict patients testing positive for SARS-CoV-2 at BAL after a negative nasopharyngeal swab. We performed a retrospective cross-sectional study with multivariable analysis of suspected patients who were tested for SARS-CoV-2 at BAL after at least one negative nasopharyngeal swab. Univariable logistic regression for odds ratio and multivariate models was calculated to determine clinical, radiological and laboratory predictors. 32/198 (16%) patients had BAL positive for SARS-CoV-2, while 65/198 tested positive for other pathogens at BAL. Of the 32 patients positive for COVID, 4 had a coinfection at BAL, being thus positive both for COVID as well as for another pathogen while the remaining 105 patients were negative for COVID and other pathogens at BAL. COVID-19 patients had more often highly suggestive CT findings, higher number of involved lobes, more often ground glass opacity of more than 50% of lung parenchyma, and less frequently other radiologically suspected infections. At multivariate model, temperature also predicted BAL positivity. The procedure was well tolerated-with only one desaturation episode-while no healthcare worker was infected. In conclusion, when nasopharyngeal swabs are negative but there is clinical or imaging suspicion of COVID-19, BAL represents a complementary diagnostic tool, particularly in conjunction with suggestive/more extensive lung involvement at CT scan. The procedure did not carry increased risks for patients nor for operators, while allowing to free hospital resources, avoiding unnecessary isolations.