Clinical characteristics of recovered COVID-19 patients with re-detectable positive RNA test

Abstract

Background: The characteristics, significance and potential cause of positive SARS-CoV-2 diagnoses in recovered coronavirus disease 2019 (COVID-19) patients post discharge (re-detectable positive, RP) remained elusive.

Methods: A total of 262 COVID-19 patients discharged from January 23 to February 25, 2020 were enrolled into this study. RP and non-RP (NRP) patients were grouped according to disease severity, and the characterization at re-admission was analyzed. SARS-CoV-2 RNA and plasma antibody levels were measured, and all patients were followed up for at least 14 days, with a cutoff date of March 10, 2020.

Results: A total of 14.5% of RP patients were detected. These patients were characterized as young and displayed mild and moderate conditions compared to NRP patients while no severe patients were RP. RP patients displayed fewer symptoms but similar plasma antibody levels during their hospitalization compared to NRP patients. Upon hospital readmission, these patients showed no obvious symptoms or disease progression. All 21 close contacts of RP patients were tested negative for viral RNA and showed no suspicious symptoms. Eighteen out of 24 of RNA-negative samples detected by the commercial kit were tested positive for viral RNA using a hyper-sensitive method, suggesting that these patients were potential carriers of the virus after recovery from COVID-19.

Conclusions: Our results indicated that young patients, with a mild diagnosis of COVID-19 are more likely to display RP status after discharge. These patients show no obvious symptoms or disease progression upon re-admission. More sensitive RNA detection methods are required to monitor these patients. Our findings provide information and evidence for the management of convalescent COVID-19 patients.

Keywords: Coronavirus; SARS-CoV-2; coronavirus disease 2019 (COVID-19).

Figure 1

Serial CT imaging of a representative RP and NRP patient. For the RP patient, the first chest CT scan on admission (day 7 since the onset of illness) showed ground-glass opacity in both lungs. At 3, 6 and 10 days after admission (day 10, day 13 and day 17 since the onset of illness), lung lesions in the chest, detected by CT imaging was significantly reduced and accompanied by the disappearance of clinical symptoms. The patient was discharged at day 12 after admission (day 19 since the onset of illness). At day 26 (day 33 since the onset of illness), the patient was re-admitted without fever and cough due to positive RNA detection. The chest CT showed no inflammatory lesions. For the NRP patient, a chest CT scan showed a small ground glass in the upper left lung on admission (day 3 since the onset of illness). On days 2 and 8 after admission (day 5 and day 11 since the onset of illness), the double lower lung lesions increased significantly, as shown by chest CT imaging, although the body temperature and the oxygenation index returned to normal levels. On days 9, 14 and 17 after admission (day 12, day 17 and day 20 since the onset of illness), CT imaging of the chest illustrate the recovery of lesions in both lower lungs. The patient was subsequently discharged without fever and cough at day 18, post admission (day 21 since the onset of illness) when SRAS-CoV-2 RNA was also detected to be negative.

Figure 2

Dynamics of SARS-CoV-2 specific antibodies. The levels of total Ab (A), IgG (B), IgA (C), and IgM (D) of different patients after illness onset. The relative antibody level was estimated using COI, expressed as the mean (denoted by columns) and SD (denoted by error bars). Red and blue columns represent RP and NRP Patients, respectively.

Figure 3

The number of discharged patients and RP patients per day from Jan 23 to March 10, 2020. On Feb 22, 2020, the anal swab negative test was added to discharge criterion. Blue indicates the number of discharge patients. Red represents the number of RP patients.