RESUMO
Rationale: Throughout recent studies, data suggests high viral load in the plasma and nasopharynx of patients with severe SARS-CoV2 infection is associated with disease severity (mortality, length of hospitalization, and risk of intubation). Here, we evaluated whether viral load in the airway is associated with poor clinical outcomes in patients with SARS-CoV2. Methods: Lower airway samples in 148 patients from an academic center that were admitted to the ICU (dates: March 10th to May 10th, 2020) with severe respiratory failure requiring mechanical ventilation and underwent bronchoscopy for airway clearance and/or tracheostomy. Clinical outcome was defined as ≤ 28 Day mechanical ventilation vs. > 28 Day mechanical ventilation vs. death. Post-admission followup time was 232 [IQR 226-237] days. RNA was isolated in parallel using zymoBIOMICS™ DNA/RNA Miniprep Kit (Cat: R2002) as per manufacturer's instructions. Viral load was measured by quantitative real-time reverse transcription polymerase chain reaction (rRT -PCR) targeting the virus nucleocapsid (N) gene and an additional primer/probe set to detect the human RNase P gene (RP). Results: Among this bronchoscopy cohort, n=58 39% of the subjects were successfully extubated within 28 days of initiation of mechanical ventilation, n=56 38% required prolonged mechanical ventilation and n=34 23% died. We evaluated the viral load by rRT-PCR for SARSCoV2 N gene adjusted by human RP gene throughout the respiratory tract using supraglottic samples and bronchoalveolar lavage (BAL) samples obtained during bronchoscopy. Paired analysis of upper and lower airway samples shows that there is a subset of subjects (n=31, 21%) where there is greater viral load in the BAL than in the supraglottic area supporting topographical differences in viral replication (Fig 1A). BAL samples from subjects that died had higher viral load in their lower airways than patients that survived, even after adjusting for confounders such as age, gender, BMI and timing of sample collection (Fig 1B magenta dots (deceased) vs. yellow/green dots (alive)). Conclusions: Using samples obtained via bronchoscopy we identified that in a subset of subjects with acute SARS-CoV2 infection, the lower airways are the predominant site for viral replication. From our study, it is unclear if the higher viral load reflects host co-morbidies (e.g., diabetes or immunosuppression) or viral factors favoring higher replication. High viral load can be used as a predictor for disease severity upon hospital admission as viral load in the lower airways correlated with poor outcomes.