Estimating the false-negative test probability of SARS-CoV-2 by RT-PCR (original) (raw)

Abstract

Introduction Reverse transcription-polymerase chain reaction (RT-PCR) assays are used to test for infection with the SARS-CoV-2 virus. RT-PCR tests are highly specific and the probability of false positives is low, but false negatives are possible depending on the individual, swab type and timing as infection progresses.

Objectives To determine how the false negative test probability in infected patients depends on the time since symptom onset and swab type.

Methods We use General Additive Mixed Models to analyse publicly available data from patients who received multiple RT-PCR tests and were identified as SARS-CoV-2 positive at least once.

Results We identify that the probability of a positive test decreases with time after symptom onset, with oropharyngeal [OP]samples less likely to yield a positive result than nasopharyngeal [NP] ones. We also comment on the likely false negative rates in cohorts of patients who present for testing at different clinical stages and assess the robustness of these estimates to the probability of false positive tests.

Conclusion NP samples are more sensitive than OP samples. The later an infected individual is tested after the onset of symptoms, the less likely they are to test positive. This has implications for identification of infected patients, contact tracing, and also for the discharge of convalescing patients who are potentially still infectious. There is an urgent need for data from asymptomatic and presymptomatic individuals.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

No particular funding supported this research.

Author Declarations

All relevant ethical guidelines have been followed; any necessary IRB and/or ethics committee approvals have been obtained and details of the IRB/oversight body are included in the manuscript.

Yes

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Yes

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Yes

I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.

Yes

Footnotes

Data Availability

All the data used in this manuscript was already in the public domain.