False Positive PCR COVID-19 Test in Montreal, Quebec, Canada

I just wanted to share a small story of a false positive PCR Covid-19 test in the hopes it helps others understand what is possible. To be clear, I have no medical background and am not trying to make any comment on the accuracy of COVID-19 tests, which I believe to be highly accurate.

On December 9^th, we were advised that there had been an outbreak of COVID-19 at our son’s daycare. Our son is 16 months old and his daycare has 10 children per group, with two instructors per group. At least one of the instructors was diagnosed with COVID-19 at that initial date. The groups were isolated (in theory) from the other children. There are a total of about 80 children at the daycare spread out over 6 groups or so. In general, the daycare seems very well run and attempts to meet all health recommendations with limitations on parents inside the daycare, hand washing and social distancing at all times.

On December 15^th, the daycare was informed of other cases of COVID-19 in our son’s group and they closed our group and kept the rest of the daycare opened. The Quebec health authorities requested that my wife, son and I get tested. We kept our son at home and did not see anyone with the exception of some visits to grocery stores and essential services. We got tested for COVID-19^th on December 18^th at 16h. We received three negative results on December 21^st at 8:30 AM. In Quebec, they administer the PCR test which is recognized as highly accurate.

On December 22^nd at 5:30 PM we were advised by the daycare that there had been 7 adults related to the daycare and 1 child in our son’s group had tested positive for COVID-19. As such, we were asked by the health authorities to get another COVID-19 test and to stay isolated until we received test results. I was working on December 23^rd, so my wife and son got tested the morning of December 23^rd. We had planned to spend Christmas with my mother-in-law, who lives by herself. We kept with that plan as we had all tested negative and had no symptoms related to COVID-19.

On December 25^th at 4PM we received a call from the health authorities that my wife had tested positive for COVID-19, but my son had tested negative. This greatly surprised us as we had no symptoms and my wife had obviously been in contact with my son. After a bit of discussion, I suspected a false positive and the article in the Lancet (PDF and another article) indicated false positives could be around 5% of PCR Tests. We decided to get retested. My mother-in-law (67 years old), my wife (32 years old) and I (37 years old) got retested on December 25^th at 5:45 PM. A nice Christmas present!

On December 27^th at 5PM we all received negative test results.

One interesting side note to this roller coaster was that we all found we had corona-virus related symptoms after the positive results. I had a mild headache and was tired, my mother-in-law had a headache and a runny nose, and my wife felt out of breath and a tight chest. Of course, this was just a case of projecting symptoms and imagining things. The human brain is a powerful organ. As soon as we got the negative results, we all suddenly felt fine!

As indicated above, I have faith and trust in the medical system and believe our healthcare workers are doing their best possible job. Mistakes happen in testing large samples and this is likely an outlying case. Throughout the process we endeavoured to respect the health guideline sand minimize our contacts and risks. As of December 28^th, we all feel fine and are enjoying the remainder of our holidays!