COVID-19: Molecular and serological investigation of 2019-nCoV infected patients

COVID-19: Molecular and serological investigation of 2019-nCoV infected patients: Spencer EA, Heneghan C

Published on July 9, 2020

Reference Zhang W, Du R-H, Li B et al. Molecular and serological investigation of 2019-nCoV infected patients: implication of multiple shedding routes. Emerging Microbes & Infections, 2020; 9:1, 386-389 2020
Study type
Country China
Setting Pulmonary hospital, Wuhan
Funding Details Mega-Project for Infectious Disease from Minister of Science and Technology of the People’s Republic of China, China Natural Science Foundation for excellent scholars, Strategic Priority Research Program of the CAS, Youth innovation promotion association of CAS.
Transmission mode Orofecal

Bottom Line

This study indicated that RNA of SARS-CoV-2 maybe shed via multiple bodily routes, and highlights that COVID-19 is found in anal swabs sometimes when oral swabs show no viral RNA.

Evidence Summary

Study Part 1. 

In summary, viral nucleotide was found in anal swab or blood even when not detected in oral swabs. Although swabs may be negative, the patient might still be viremic.

Among 15 patients still testing positive after several days of medical treatment, eight were oral swabs positive (53%), four were anal swabs positive (27%), six blood positives (40%) and three serum positives (20%). 

Two patients were positive by both oral swab and anal swab, yet none of the blood positive were also swabs positive. All serum positives were also whole serum positive. 

Study Part 2.

On the first day of sampling, both IgM and IgG titres were relatively low or undetectable 

On day 5, an increase of viral antibodies was observed among nearly all patients. 

IgM positive rate increased from 50% (8/16) to 81% (13/16), whereas IgG positive rate increased from 81% (13/16) to 100% (16/16). 

This contrasted with to a relatively low detection positive rate from molecular testing

The serology test altered the positive detection rate.  

What did they do?

A study of two parts, using samples collected from COVID-19 patients in a pulmonary hospital in Wuhan. 

Two investigations were performed. In the first investigation, samples were collected from 39 COVID-19 patients, seven of which were seriously ill. In the second investigation, samples were collected from COVID-19 patients, whose clinical records were not available. 

Data were reported only for patients who tested viral nucleotide positive. 

Part 1:

This study investigated whether viral RNA can be found in anal swabs and blood as well as oral swabs. Among 15 patients diagnosed via positive oral swab, blood, oral swabs and anal swabs were compared. 

Part 2:

This study examined the dynamic changes of viral presence in oral and anal swabs in the second group of patients. Study participants were 16 patients who received around 10 days of medical treatments upon admission. 

Viral antibody and viral nucleotide levels were measured for these patients. 

Study reliability

It is unclear how the study samples were selected and if bias could have been introduced in the sampling. The method sections was limited

Clearly defined setting Demographic characteristics described Follow-up length was sufficient Transmission outcomes assessed Main biases are taken into consideration
Yes Yes Unclear Unclear Unclear

What else should I consider?

More anal swab positives than oral swab positives were found among patients in a later stage of infection, suggesting shedding and thereby transmission through orofaecal route.  The individual patient data is reported in supplements to the paper and fully available.

About the authors

Carl Heneghan

Carl is Professor of EBM & Director of CEBM at the University of Oxford. He is also a GP and tweets @carlheneghan. He has an active interest in discovering the truth behind health research findings

Elizabeth Spencer

Dr Elizabeth Spencer; MMedSci, PhD. Epidemiologist, Nuffield Department for Primary Care Health Sciences, University of Oxford.