Data and source code at https://framagit.org/saji_nh/jp_pcr
The source code, data, and images may be freely used without permission. However, the original data for PCR tests and related statistics were compiled by Toyo Keizai, and their efforts should be acknowledged by citing their data repository https://github.com/kaz-ogiwara/covid19.
Questions and comments may be addressed to Saji N. Hameed by email (saji'at-mark'u-aizu.ac.jp)

PCR positives without Testing

PCR positives reported without tests

Data source

The data analyzed here is the PCR data reported for each of the 47 Japanese prefecture, and is taken from https://github.com/kaz-ogiwara/covid19/blob/master/README.md

What is reported here?

The data contains some data points where the number of positive PCR counts equal or exceeds the number of PCR tests. Since positive PCR results are always reported along with a test, this disparity needs to be documented and investigated.

  1. In the table below, a summary is provided where the percentage of times this happens is the last column.

  2. The prefectures where this anomaly happens most can be found towards the top of the table.

  3. The total number of positives and tests in such suspicious data points is also provided.

  4. Please click on the prefecture to open a plot which shows the dates at which these suspicious data points are found (top figure).

    • the bottom figure on the plot shows the daily positive PCR counts as the vertical bars. The thick line is the percentage of positive PCR counts relative to the total tests.
    • the background shading on the plots show periods where testing policy has changed. Initially, the PCR tests were carried out on swabs of nasal and throat mucus in symptomatic people (fever above 37.5 C sustained for 3 days or more).
    • The yellow region shows the period when this policy was changed to PCR testing on saliva from symptomatic people.
    • Then on July 17 (grey shade), the PCR tests could be done from saliva swabs on anyone (asymptomatic or symptomatic).
Prefecture No of PCR positives No of PCR tests Percentage of bad points
Kanagawa 1846 -1292 31.7
Nara 447 -4404 28.8
Ibaraki 275 0 19.4
Okayama 192 0 16.5
Hiroshima 244 0 16.2
Aichi 1267 0 14.4
Okinawa 1068 -9655 12.6
Mie 161 0 10.8
Toyama 123 -163 10.4
Nagano 60 1 8.3
Ishikawa 143 0 8.3
Chiba 352 90 8.3
Akita 41 6 6.8
Miyazaki 122 7 6.5
Kyoto 101 2 5.8
Kagoshima 95 0 5.4
Shiga 39 9 5.4
Saitama 264 43 5.4
Kumamoto 99 0 5.0
Shizuoka 122 0 5.0
Gunma 73 8 4.7
Fukushima 34 1 4.7
Fukuoka 258 50 4.3
Niigata 40 -138 4.3
Fukui 43 10 4.0
Tokyo 921 276 3.6
Yamagata 28 1 3.6
Miyagi 41 0 3.6
Hyogo 89 21 3.2
Yamanashi 19 0 3.2
Gifu 32 6 2.9
Tochigi 18 2 2.9
Nagasaki 23 1 2.5
Yamaguchi 25 0 2.5
Wakayama 22 3 2.5
Saga 11 0 2.2
Kochi 12 1 1.8
Ehime 8 0 1.8
Kagawa 8 0 1.8
Oita 12 0 1.4
Shimane 6 0 1.1
Tottori 4 0 1.1
Aomori 10 0 0.7
Tokushima 1 -148 0.4
Osaka 0 0 0.0
Iwate 0 0 0.0
Hokkaido 0 0 0.0