- For SARS-CoV-2 testing, false-negative rates with PCR testing appear to be lowest at 3 days after symptom onset or ~8 days postexposure, according to this review and analysis of 7 studies.
- Even at those time points, false-negative rates are 1 in 5.
Why this matters
- SARS-CoV-2 RT-PCR test results may not offer a rationale for removing transmission precautions, especially in the early days of symptoms.
- Consider waiting 1-3 days after symptom onset before conducting SARS-CoV-2 RT-PCR testing to minimize false-negatives.
- If clinical suspicion is high, do not rule out infection based on testing alone.
- 7 studies (2 preprints; 5 peer-reviewed), 1330 respiratory samples.
- During 4 days of infection before symptom onset (day 5), false-negative probability (95% CIs) decreased from 100% (100%-100%) on day 1 to 67% (27%-94%) on day 4.
- Median (95% CIs) false-negative rates:
- Day of symptom onset: 38% (18%-65%).
- Day 8 (3 days after symptom onset): 20% (12%-30%).
- Day 9: 21% (13%-31%).
- Day 21: 66% (54%-77%).
- Sensitivity analysis: highest probability of infection despite negative RT-PCR would occur on day 2 (12.4%).
- Literature review and pooled analysis estimating predictive value/false-negative rate by day of SARS-CoV-2 RT-PCR based on time from exposure, symptom onset.
- Funding: NIH, others.
- Study heterogeneity, including design, sample collection techniques.
- Limited generalizability.
- Underestimated true false-negatives.