[Tilted Irish Kilt]

trisham :" I wonder how often this kind of thing happens? Lately, it seems that it’s not unusual."

In the first place, the initial testing was done in a local, District of Columbia, District health facility,
This is where the mathematical calculation error occurred, at the local level.
Subsequently, after finding the calculation error, the same blood tests were submitted to the CDC (the national medical authority) for re-test where the false negatives were found.
Statistically, the error rate on the re-test by the CDC was only less than 3.5% for the samples re-tested; however that is little consolation for those given a clean bill of health
only to find out some nine months later that they carried the virus.
This announcement by the District and the CDC points out the need for frequent , or occasional, review of medical testing protocols on the local level.

[trisham]

I couldn’t agree more, TIK.