This is week 149 of the COVID apocalypse. How the time flies! Here is Dr. Klotman’s weekly COVID update. The highlights are:

  • Test positivity rates, hospitalizations, deaths and even wastewater antigen levels have levelled off and are falling across the US.
  • The Omicron subvariant XBB.1.5 continues to spread across the US albeit slowly.
  • Bivalent COVID vaccine uptake among folks <65+ is low at about 30%+.
  • Multisystem Inflammatory Syndrome in Children (MIS-C) infected with COVID has not been associated with COVID vaccines. Neither MIS-C nor fear of mild myocarditis are reasons to forego vaccinating our kids.

Other COVID news not in Dr. Klotman’s update includes:

  • Bivalent m-RNA COVID vaccines confer ~50% reduction in COVID infections among adults including seniors. The effectiveness of these vaccines in preventing hospitalization is probably greater (as it has been with other boosters), but we don’t have enough data yet to make that claim.
  • At Home COVID antigen tests have a high false-negative rate in asymptomatic infections as well as in early symptomatic infections – more on this below.
  • Florida Governor Ron Desantis has been spewing COVID misinformation (again). He has claimed that vaccination with the bivalent COVID vaccines makes folks more susceptible to COVID. His claim and its sources are a clear case of confirmation bias – the result of looking for sources that support a preconceived notion while ignoring sources that contradict that bias. The studies that he cites have not undergone peer review and are likely flawed as they are contradicted by the vast majority of peer reviewed studies.

About Tests

All tests have false positives and false negatives. That is, a blood test, pregnancy test, MRI or a biopsy all have some associated rate of tests that are positive when the condition they test for is ABSENT (False Positive.) The converse is also true; every test has some rate of negative results when the condition is PRESENT (False Negative). In the case of at home COVID tests, False Negatives are common – the test says that you don’t have COVID when actually you do. COVID test false positive results are much less common.

So, what’s the point of testing? If you are coughing and having fever, and your COVID test result is negative. Retest in a day or two. If it is still negative but you are still having symptoms, test the next day. If you have three negative test results over as many days, you probably don’t have COVID. If any of those tests is positive, you must assume that you actually have COVID.

Now, there is another factor to consider, and that is the population prevalence of the condition that the test is for. In the case of COVID testing, if COVID is very uncommon in your area and you have a negative test, the odds are good that you don’t have COVID. If your community is experiencing a spike in COVID cases, and your test is negative, all bets are off. Your negative result needs to be confirmed because it could well be a false negative.

I could show you the math for test results, true and false positives and negatives as well as positive and negative predictive values, but the odds are that those who want to know the math already know it, and those who aren’t interested in the math minutia would probably rather have a cup of hemlock. I recommend an adult beverage instead.

By: llcPosted on