OBJECTIVE Concerns have been raised that patients with Coronavirus Disease 2019 (COVID-19) are still infectious with a re-positive nucleic acid test of the pharyngeal swab after hospital discharge. The aim of this study was to investigate the clinical relevance of induced sputum as an additional indicator for the current clinical discharge criteria of COVID-19 patients to prevent virus recurrence. PATIENTS AND METHODS Twenty-one COVID-19 patients who met the national clinical discharge criteria were discharged from the hospital and tested daily for the presence of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) nucleic acid in their pharyngeal swabs and every other day for the presence of SARS-CoV-2 in their induced sputum. Once the patient's induced sputum was negative after two consecutive tests, testing was discontinued. RESULTS Among 21 discharged patients from COVID-19, the first pharyngeal swab and induced sputum tests for viral nucleic acid were positive in 3 (14.3%) and 8 (38.1%) patients respectively. Induced sputum was significantly more positive than pharyngeal swab (p < 0.05). In our cohort, all pharyngeal swabs became negative at day 7, and all induced sputa turned negative at day 11 after discharge. Interestingly, patients with negative pharyngeal swabs experienced viral relapse, whereas patients with negative induced sputum did not revert to positivity. CONCLUSIONS The detection rate of positive viral nucleic acid in induced sputum was high. Patients with negative induced sputum nucleic acid tests did not have a relapse of SARS-COV-2, indicating that viral nucleic acid testing of induced sputum should be used as an additional criterion for patients with national clinical discharge criteria COVID-19.
Negative viral nucleic acid test of induced sputum: an additional criteria for COVID-19 patient's discharge.