Development and validation of an individualized nomogram for early prediction of the duration of SARS-CoV-2 shedding in COVID-19 patients with non-severe disease

With the number of cases of coronavirus disease-2019(COVID-19)increasing rapidly,the World Health Organization(WHO)has recommended that patients with mild or moderate symptoms could be released from quarantine without nucleic acid retesting,and self-isolate in the community.This may pose a potential virus transmission risk.We aimed to develop a nomogram to predict the duration of viral shedding for individual COVID-19 patients.This retrospective multicentric study enrolled 135 patients as a training cohort and 102 patients as a validation cohort.Significant factors associated with the duration of viral shedding were identified by multivariate Cox modeling in the training cohort and combined to develop a nomogram to predict the probability of viral shedding at 9,13,17,and 21 d after admission.The nomogram was validated in the validation cohort and evaluated by concordance index(C-index),area under the curve(AUC),and calibration curve.A higher absolute lymphocyte count(P=0.001)and lymphocyte-to-monocyte ratio(P=0.013)were correlated with a shorter duration of viral shedding,while a longer activated partial thromboplastin time(P=0.007)prolonged the viral shedding duration.The C-indices of the nomogram were 0.732(95%confidence interval(CI):0.685-0.777)in the training cohort and 0.703(95%CI:0.642-0.764)in the validation cohort.The AUC showed a good discriminative ability(training cohort:0.879,0.762,0.738,and 0.715 for 9,13,17,and 21 d;validation cohort:0.855,0.758,0.728,and 0.706 for 9,13,17,and 21 d),and calibration curves were consistent between outcomes and predictions in both cohorts.A predictive nomogram for viral shedding duration based on three easily accessible factors was developed to help estimate appropriate self-isolation time for patients with mild or moderate symptoms,and to control virus transmission.