The additional value of lower respiratory tract sampling in the diagnosis of COVID-19. A single centre real life observational study.

Abstract Background: Since December 2019 SARS-CoV-2 has been identified as the causal agent for severe cases of pneumonia in China and it spread all over the world, putting great pressure on Health Systems. Despite regarded as the standard procedure, sensitivity of nasopharyngeal swab (NPS) is suboptimal. In clinical/radiological suspicion of SARS-CoV-2 infection despite negative NPS test, other tests may be required to rule out the infection. Objectives: To evaluate correlations between lower respiratory tract (LRT) testing for SARS-CoV-2 in suspect patients with 2 negative NPSs and clinical symptoms, laboratory values and the CT scan review score by the Radiological Society of North America. Method: Retrospective analysis of radiological, clinical and laboratory data from patients who underwent LRT sampling (blind nasotracheal aspiration or bronchial washing) for suspected COVID-19 after 2 negative NPS. Chest CTs were reviewed by two blinded radiologist using the Radiological Society of North America score for analysis purpose.Results: SARS-CoV-2 was detected in 7 out of 59 patients (11.9%). No clinical or laboratory value were found to correlate with positive test. CT scan showed good sensitivity (71.4%) and accuracy (81.3%), with a very high NPV (95.7%). Features scored as 'typical' showed good correlation with SARS-CoV2 detection on LRT. No complications nor staff’s infections were reported. Conclusions: In suspect cases with at least 2 negative swabs CT scan revision can be helpful in ruling out SARS-CoV-2 infection. In selected cases lower respiratory tract sampling can help in confirming COVID-19 in cases with consistent CT features.