Clin Microbiol Infect. 2021 Feb 8:S1198-743X(21)00055-0. doi: 10.1016/j.cmi.2021.01.028. Online ahead of print.
OBJECTIVES: Re-positive tests for SARS-CoV-2 in Coronavirus Disease 2019 (COVID-19) patients were common. We aimed to investigate the rate and risk factors of recurrent positive detection of SARS-CoV-2 in hospitalized COVID-19 patients.
METHODS: Oropharyngeal and nasopharyngeal swabs (n=3513) were collected to detect SARS-CoV-2 during the hospitalization. We analyzed the recurrent positive rate after consecutive negative results and its relationship to demographic characteristics.
RESULTS: Among 599 enrolled COVID-19 patients, the median time for viral RNA shedding was 24 days (IQR, 19-33 days). The positive rate of RT-PCR was 35.9% (215/599), 17.0% (65/383) and 12.4% (23/185) after one, two and three consecutive negative RT-PCR test results respectively. Medians of CT-values of initial positive test, rebound positive after two consecutive negative results, and rebound positive after three consecutive negative results were 28.8, 32.8 and 36.1 respectively. Compare with male patients, females had a significant higher rate of recurrent positive RT-PCR after three consecutive negative results (18.2%, 18/99 vs. 5.8%, 5/86, p=0.013). Older age (≥55 yrs) had a significant higher rate of recurrent positive RT-PCR after one negative result (42.3%, 165/390, vs. 23.9%, 50/209, p<0.001). Nasopharyngeal swab tests produced a higher positive rate than oropharyngeal swab tests (37.3%, 152/408 vs. 35.8%, 1111/3105).
CONCLUSIONS: Our study revealed the prevalence and dynamic characteristics of recurrent positive RT-PCR to SARS-CoV-2. We showed that around 17.0% (65/383) patients were tested positive for SARS-CoV-2 after two consecutive negative results. Patients with rebound positive RT-PCR test had a low viral load. Older age and female were risk factors for recurrent positive results.