Lin (2020)
Early risk factors for the duration of SARS-CoV-2 viral positivity in COVID-19 patients
Laboratory Findings
IL-6 (Above median vs. Below median)
Virus clearance
Hazard ratio: 0.859 (0.394-1.874) Adjusted model


Prospective cohort study

Medical records


A cohort of 137 laboratory confirmed COVID-19 patients were prospectively enrolled from January 19th 2020 to March 9th 2020. All patients were admitted and treated in Taizhou Hospital of Zhejiang Province, Taizhou Enze Hospital, Taizhou EnZe Medical Group (Center), Zhejiang, China.

Of these 137 COVID-19 patients (73 male and 64 female), there were 1 critical, 22 severe, and 114 ordinary cases with the median age of 47 years (range: 4~86 years). A significantly shorter SARS-CoV-2 viral positivity duration was related to younger (mean: 12.7 days vs 16.6 days; p = 0.011) with the median age of 47 years as a cut-off value, while a much shorter but not reach statistical significant when use the age above 60 years as a cut-off (14.2 days vs 16.9 days, p = 0.190). A markedly shorter viral positivity duration was also related to not severe patient (13.9 days vs 18.4 days; p = 0.060), higher count of lymphocytes (13.1 days vs 16.8 days; p = 0.024), eosinophils (12.3 days vs 16.3 days; p = 0.014), and CD8+ T cells (11.8 days vs 16.8 days; p = 0.022), and lower levels of IL-6 (11.9 days vs 16.2 days; p = 0.026) and IL-10 (11.7 days vs 16.2 days; p = 0.014), respectively.


50 Day

Virus clearance


Consecutive virus screening (sampling interval at least 1 day) was performed with RT-PCR during the period of hospitalization. SARS-CoV-2 returned to negative (sampling interval at least 1 day) were determined with at least consecutive two times of the RT-PCR negative results.

Laboratory Findings


(pg/mL). <6.75 vs >6.75

Below median

Above median

Hazard ratio

0.859 (0.394-1.874)




Age, Severity, Lymphocyte count, Eosinophil count, Immune cell subsets - cluster of differentiation like CD3+ T cell, CD4+ T cell, CD8+ T cell, Eosinophil count, Cytokines Interleukin like Interleukin-6, Interleukin-10

Cox regression proportional-hazards model was applied to assess the hazard ratio (HR) of each variable for the duration of SARS-CoV-2 viral positivity, and significant risk factors whose HR was further adjusted with covariate analysis. Multivariate analysis after adjusted covariables, the count of CD8+ T cells was the predominant risk factor for the duration of SARS-CoV-2 viral positivity.