key: cord-0874097-7r3hougf
authors: Tsukadaira, A.
title: The specificity of Japanese PCR assays for SARS-CoV-2 exceeds 99.7%
date: 2020-05-20
journal: nan
DOI: 10.1101/2020.05.15.20103515
sha: fb00d462205bbdf82d4d4d594deda99ec8e72708
doc_id: 874097
cord_uid: 7r3hougf

The Japanese government arranged a total of three charter flights to evacuate Japanese residents out of Wuhan Jan 29, 30, and 31, 2020. The project to rescue Japanese residents can be recognized as a randomized sampling study for the COVID-19 epidemic in Wuhan at that time. Jan 23, Jonathan MR et al stated in the medRxiv, in 14 days time (Feb 4, 2020), the number of infected people in Wuhan is estimated to be greater than 190 thousand (prediction interval, 132,751 to 273,649). In our study, the estimation of the COVID-19 cases in Wuhan around Jan 29, 30 and 31, 2020 exceeds the lower prediction 132,751 in the prior probability: 0.0134. Our statistical analysis is consistent with Jonathan MR et al, if the specificity of SARS-CoV-2 PCR assays in Japan exceeds 99.7%.

aspirate specimens), 65% and 72% (throat swab specimens), respectively (3). The National Institute of Infectious Diseases (NIID) in Japan states that the PCR assays for SARS-CoV-2 is highly specific, but the exact sensitivity and specificity are still unknown.

The project to rescue Japanese residents can be recognized as a randomized sampling study for the COVID-19 epidemic in Wuhan at that time. The prior probability of statistics in Wuhan is unknown, however the following formula can be used for the back calculation. Table 2 shows statistical probability formulas assuming the sensitivity of SARS-CoV-2 PCR assays for nasopharyngeal and throat swab is 70%.

As of Jan 31, 2020, 192 deaths were reported, and 3215 positive COVID-19 cases were confirmed COVID-19 by examination in Wuhan (4) (5). If the specificity is 99.00 to 99.99%, a projected estimate of COVID-19 cases in Wuhan, a city with a population of 11 million, is shown on Table 3 (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted May 20, 2020 . . https://doi.org/10.1101 Tables Table 1 . The breakdown of the 3 flights for Japanese residents evacuated from Wuhan on Jan 29, 30, and 31, 2020 Table 2 . Formula of prior probability when the sensitivity is 0.7 and the unknown specificity is a.

Sensitivity: 0.7 Specificity: a 0.7x + (1-a) (566-x) = 7

The true patient count (positives and false negatives): x Prior probability: x/566 Table 3 .

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(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. All rights reserved. No reuse allowed without permission.

(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted May 20, 2020 . . https://doi.org/10.1101 

National Institute of Infectious Diseases in Japan Open Data

No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted

No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity

A.T. and K.N. received no funding Authors' contributions All authors conceived the study and participated in the study design. A.T. collected and analysed the data.A.T. and K.N. drafted the manuscript and revised the the earlier versions of the manuscript. All authors edited the manuscript and approved the final version.

The authors declare no conflicts of interest.