SARS-CoV-2 viral load dynamics and real-time RT-PCR cycle threshold interpretation in symptomatic non-hospitalised individuals in New Zealand: a multicentre cross sectional observational study.

Autor: Fox-Lewis A; Microbiology Department, LabPLUS, Auckland City Hospital, Auckland District Health Board, Auckland, New Zealand., Fox-Lewis S; Virology-Immunology Department, LabPLUS, Auckland City Hospital, Auckland District Health Board, Auckland, New Zealand. Electronic address: afoxlewis@gmail.com., Beaumont J; Microbiology Department, Middlemore Hospital, Counties Manukau District Health Board, Auckland, New Zealand., Drinković D; Microbiology Department, North Shore Hospital, Waitematā District Health Board, Auckland, New Zealand., Harrower J; Auckland Regional Public Health Service, Auckland District Health Board, Auckland, New Zealand., Howe K; Auckland Regional Public Health Service, Auckland District Health Board, Auckland, New Zealand., Jackson C; Nga Tai Ora Public Health Northland, Northland District Health Board, Whangarei, New Zealand., Rahnama F; Virology-Immunology Department, LabPLUS, Auckland City Hospital, Auckland District Health Board, Auckland, New Zealand., Shilton B; Labtests, Auckland, New Zealand., Qiao H; Microbiology Department, Middlemore Hospital, Counties Manukau District Health Board, Auckland, New Zealand., Smith KK; Microbiology Department, North Shore Hospital, Waitematā District Health Board, Auckland, New Zealand., Morpeth SC; Microbiology Department, Middlemore Hospital, Counties Manukau District Health Board, Auckland, New Zealand., Taylor S; Microbiology Department, Middlemore Hospital, Counties Manukau District Health Board, Auckland, New Zealand., Blakiston M; Microbiology Department, LabPLUS, Auckland City Hospital, Auckland District Health Board, Auckland, New Zealand; Labtests, Auckland, New Zealand., Roberts S; Microbiology Department, LabPLUS, Auckland City Hospital, Auckland District Health Board, Auckland, New Zealand., McAuliffe G; Virology-Immunology Department, LabPLUS, Auckland City Hospital, Auckland District Health Board, Auckland, New Zealand; Labtests, Auckland, New Zealand.
Jazyk: angličtina
Zdroj: Pathology [Pathology] 2021 Jun; Vol. 53 (4), pp. 530-535. Date of Electronic Publication: 2021 Mar 20.
DOI: 10.1016/j.pathol.2021.01.007
Abstrakt: We conducted a multicentre cross sectional observational study of laboratory, public health and hospitalisation data for PCR-confirmed COVID-19 cases within the New Zealand Northern Region, between 12 February and 8 June 2020. The aim of this study was to describe population level SARS-CoV-2 upper respiratory tract (URT) viral load dynamics by stratifying positivity rates and polymerase chain reaction (PCR) cycle threshold (Ct) values of URT samples from COVID-19 cases by days since symptom onset, and to explore utility of Ct values in determining length of time post-infection and thus potential infectivity. Of 123,124 samples tested for SARS-CoV-2 by PCR, 579 samples (407 positive and 172 negative) from 368 symptomatic non-hospitalised individuals with PCR-confirmed infection were included. Sample positivity rate was 61.5% (8/13) for pre-symptomatic samples, rising to 93.2% (317/340) for samples collected during the purported symptomatic infectious period (days 0-10 post-symptom onset), and dropping to 36.3% (82/226) for post-infectious period samples (day 11 onwards). URT viral load peaked shortly after symptom onset, with median Ct values ranging 20.00-29.99 until 15 days post-symptom onset, and >30.00 after this time. Of samples with a Ct value of <20.00, 96.1% were collected during the symptomatic infectious period. However, of samples with a Ct value ≥30.00 and ≥35.00, 46.9% and 18.5%, respectively, were also collected during the symptomatic infectious period. The findings of this study indicate that at or soon after symptom onset represents the optimum time to test for SARS-CoV-2 in the URT, with median Ct values suggesting the useful testing window extends until around 15 days post-symptom onset. In asymptomatic individuals or those with unknown dates of symptom onset, Ct values <20.00 imply recent onset/potential infectivity, but Ct values ≥30.00 or ≥35.00 do not exclude recent onset/potential infectivity. Individual sample Ct values should not be used as an absolute marker of length of time post-infection or to exclude infectivity where date of symptom onset is unavailable.
(Copyright © 2021 Royal College of Pathologists of Australasia. Published by Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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