The medical officer of health for Chatham-Kent says false COVID-19 positives are just part of the testing process.
Dr. David Colby answered questions about the issue at a weekly media teleconference on Thursday after four false positive coronavirus tests were reported on Wednesday. Colby said all medical tests have false positives and false negatives because there's no perfect test out there. He said some positive cases get retested for various reasons and if a recent positive case retests as a negative he orders a third test.
If the third test is negative and the person is asymptomatic and not a contact, then they would be cleared and the total number of cases would drop by one.
Colby once again emphasized that diagnostic testing doesn't work well on low-risk populations. He added the test performs very well and the public can have confidence in the test as long as it is used in a diagnostic capacity -- testing symptomatic people or those exposed to a case more than five days before.
"If you apply a diagnostic test broadly to a low-risk population then you get into a situation where the false positives can outnumber the true positives," said Colby. "When you start testing people who are not contacts of cases, they're asymptomatic, and they're perfectly healthy then you're going to get these false positives."
Colby said usually he doesn't question positive tests because most of them are contacts of other active cases. He added tests must be fully investigated before they're declared false or positive and sometimes there are surprises.
"You don't report false reports of fire, you wait until that's actually confirmed before you make it into a news story," the doctor said.
Colby added people who have a false-positive test are isolated until the result is verified.
The numbers reported by CK Public Health on Wednesday also included 10 recovered cases and the release of three people from hospital after recovering from the virus. The last person was reported out of the hospital on Thursday.
Active cases across Chatham-Kent went from 54 to 40 between Tuesday and Wednesday and were down to 39 on Thursday.
