今回、米国ジョンズ・ホプキンズ大学のLauren M. Kucirka氏らが7つの研究のプール解析を行ったところ、偽陰性率は、発症後3日目(感染後8日目)に最も低くなることがわかった。著者らは、偽陰性の可能性を最小限にするために、検査は発症から3日間待って実施すべきとしている。また、臨床的にCOVID-19が疑われる場合は、PCR陰性のみで除外診断すべきではなく、臨床的および疫学的状況を慎重に検討する必要があると述べている。Annals of Internal Medicine誌オンライン版2020年5月13日号に掲載。






Variation in False-Negative Rate of Reverse Transcriptase Polymerase Chain Reaction-Based SARS-CoV-2 Tests by Time Since Exposure.JournalAnnals of internal medicine. 2020 May 13; doi: 10.7326/M20-1495.AuthorLauren M Kucirka, Stephen A Lauer, Oliver Laeyendecker, Denali Boon, Justin LesslerAbstract

BACKGROUND : Tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) based on reverse transcriptase polymerase chain reaction (RT-PCR) are being used to “rule out” infection among high-risk persons, such as exposed inpatients and health care workers. It is critical to understand how the predictive value of the test varies with time from exposure and symptom onset to avoid being falsely reassured by negative test results.

RESULTS : Over the 4 days of infection before the typical time of symptom onset (day 5), the probability of a false-negative result in an infected person decreases from 100% (95% CI, 100% to 100%) on day 1 to 67% (CI, 27% to 94%) on day 4. On the day of symptom onset, the median false-negative rate was 38% (CI, 18% to 65%). This decreased to 20% (CI, 12% to 30%) on day 8 (3 days after symptom onset) then began to increase again, from 21% (CI, 13% to 31%) on day 9 to 66% (CI, 54% to 77%) on day 21.

LIMITATION : Imprecise estimates due to heterogeneity in the design of studies on which results were based.

CONCLUSION : Care must be taken in interpreting RT-PCR tests for SARS-CoV-2 infection-particularly early in the course of infection-when using these results as a basis for removing precautions intended to prevent onward transmission. If clinical suspicion is high, infection should not be ruled out on the basis of RT-PCR alone, and the clinical and epidemiologic situation should be carefully considered.

PRIMARY FUNDING SOURCE : National Institute of Allergy and Infectious Diseases, Johns Hopkins Health System, and U.S. Centers for Disease Control and Prevention.