Temporal profile and determinants of viral shedding and of viral clearance confirmation on nasopharyngeal swabs from SARS-CoV-2-positive subjects: a population-based prospective cohort study in Reggio Emilia, Italy
,
Carlo Salvarani,
Giulio Formoso,
Massimo Vicentini,
Cinzia Campari,
Rossana Colla,
Carmine Pinto,
Pamela Mancuso,
Marco Massari,
Massimo Costantini,
Paolo Giorgi Rossi,
Francesco Venturelli,
Cinzia Perilli,
Elisabetta Larosa,
Eufemia Bisaccia,
Emanuela Bedeschi,
Alessandro Zerbini,
Roberto Grilli,
Serena Broccoli,
Anna Maria Ferrari,
Massimiliano Marino,
Laura Trabucco,
Debora Formisano,
Lucia Spaggiari,
Marta Ottone,
Nicola Facciolongo,
Giulia Besutti,
Pierpaolo Pattacini,
Ivano Venturi,
Francesco Gioia,
Valentina Iotti,
Andrea Nitrosi,
Marco Foracchia,
Mirco Pinotti,
Ivana Lattuada,
Stefano De Pietri,
Giorgio Francesco Danelli,
Laura Albertazzi,
Enrica Bellesia,
Simone Canovi,
Mattia Corradini,
Tommaso Fasano,
Elena Magnani,
Annalisa Pilia,
Alessandra Polese,
Silvia Storchi Incerti,
Piera Zaldini,
Efrem Bonelli,
Bonanno Orsola,
Matteo Revelli,
Chiara Seidenari,
Licia Veronesi,
Paola Affanni,
Maria Eugenia Colucci
Affiliations
Carlo Salvarani
13 Rheumatology Unit, Azienda Unità Sanitaria Locale-IRCCS di Reggio Emilia, Reggio Emilia, Italy
Giulio Formoso
Clinical Governance Unit, Azienda USL – IRCCS di Reggio Emilia, Reggio Emilia, Emilia-Romagna, Italy
Massimo Vicentini
1 Epidemiology Unit, Azienda USL-IRCCS di Reggio Emilia, Reggio Emilia, Emilia-Romagna, Italy
Cinzia Campari
Rossana Colla
Carmine Pinto
Pamela Mancuso
Epidemiology Unit, Azienda USL - IRCCS di Reggio Emilia, Reggio Emilia, Italy
Marco Massari
Azienda USL-IRCCS di Reggio Emilia, Reggio Emilia, Italy
Massimo Costantini
Paolo Giorgi Rossi
1 Epidemiology Unit, Azienda USL-IRCCS di Reggio Emilia, Reggio Emilia, Emilia-Romagna, Italy
Francesco Venturelli
Epidemiology Unit, Azienda Unità Sanitaria Locale-IRCCS di Reggio Emilia, Reggio Emilia, Italy
Cinzia Perilli
3 Public Health Service, Azienda USL-IRCCS di Reggio Emilia, Reggio Emilia, Italy
Elisabetta Larosa
3 Public Health Service, Azienda USL-IRCCS di Reggio Emilia, Reggio Emilia, Italy
Eufemia Bisaccia
3 Public Health Service, Azienda USL-IRCCS di Reggio Emilia, Reggio Emilia, Italy
Emanuela Bedeschi
3 Public Health Service, Azienda USL-IRCCS di Reggio Emilia, Reggio Emilia, Italy
Alessandro Zerbini
Unit of Clinical Immunology, Allergy and Advanced Biotechnologies, Azienda Unità Sanitaria Locale - IRCCS di Reggio Emilia, Reggio Emilia, Italy
Roberto Grilli
Serena Broccoli
Anna Maria Ferrari
Emergency Department, Azienda USL - IRCCS di Reggio Emilia, Reggio Emilia, Emilia-Romagna, Italy
Massimiliano Marino
Clinical Governance Unit, Azienda USL – IRCCS di Reggio Emilia, Reggio Emilia, Emilia-Romagna, Italy
Laura Trabucco
Debora Formisano
Lucia Spaggiari
Radiology Unit, Department of Diagnostic Imaging and Laboratory Medicine, Azienda USL - IRCCS di Reggio Emilia, Reggio Emilia, Italy
Marta Ottone
Epidemiology Unit, Azienda USL - IRCCS di Reggio Emilia, Reggio Emilia, Italy
Nicola Facciolongo
Giulia Besutti
Radiology Unit, Department of Diagnostic Imaging and Laboratory Medicine, Azienda USL - IRCCS di Reggio Emilia, Reggio Emilia, Italy
Pierpaolo Pattacini
Radiology Unit, Department of Diagnostic Imaging and Laboratory Medicine, Azienda USL - IRCCS di Reggio Emilia, Reggio Emilia, Italy
Ivano Venturi
Francesco Gioia
Valentina Iotti
Andrea Nitrosi
Marco Foracchia
Mirco Pinotti
Ivana Lattuada
Stefano De Pietri
Giorgio Francesco Danelli
Laura Albertazzi
Enrica Bellesia
Simone Canovi
Mattia Corradini
Tommaso Fasano
1 Clinical Pathology Unit, AUSL della Romagna, Pievesestina-Cesena, Italy
Elena Magnani
Annalisa Pilia
Alessandra Polese
Silvia Storchi Incerti
Piera Zaldini
Efrem Bonelli
Bonanno Orsola
Matteo Revelli
Radiology Unit, Department of Diagnostic Imaging and Laboratory Medicine, Azienda USL - IRCCS di Reggio Emilia, Reggio Emilia, Italy
Objectives To determine the timing of viral clearance (first negative RT-PCR on nasopharyngeal swab) and the probability of viral clearance confirmation (two consecutive negative swabs) in COVID-19 patients and to identify related determinants.Design Population-based prospective cohort study on archive data.Setting Preventive services and hospital care in the Reggio Emilia province, northern Italy.Participants All 1162 subjects testing positive to RT-PCR on nasopharyngeal swabs and diagnosed with COVID-19 in the Reggio Emilia province with at least 30 days of follow-up by 22 April 2020.Main outcome measures Median times from diagnosis and from symptom onset to viral clearance with IQR assessed using the Kaplan–Meier estimator, stratified by included characteristics. The probability of viral clearance confirmation, stratified by time from diagnosis and putative determinants assessed using a multivariate logistic regression model.Results Viral clearance was achieved by 60.6% (704/1162) of patients, with a median time of 30 days from diagnosis (IQR 23–40) and 36 days from symptom onset (IQR 28–45). Of those negative and retested, 78.7% (436/554) had viral clearance confirmation, suggesting one in five false negative tests. The time from symptom onset to viral clearance slightly increased with age, from 35 (IQR 26–44) days under age 50 to 38 (IQR 28–44) in over age 80, and with disease severity, from 33 (IQR 25–41) days in non-hospitalised subjects to 38 (IQR 30–47) days in hospitalised patients. The probability of confirmed viral clearance reached 86.8% after 34 days from symptom onset and increased with time, even when adjusting for age and sex (OR 1.16 95% CI 1.06 to 1.26 per day from diagnosis).Conclusions Postponing follow-up testing of clinically recovered COVID-19 patients could increase the efficiency and performance of testing protocols. Understanding viral shedding duration also has implications for containment measures of paucisymptomatic subjects.