Just two episodes of TWiM under my belt and have been delighted. It is amazing how well a non-chemist can visualize chemical/cellular processes from the TWiM podcasts! Thanks.
Episode 216 “starts with a cough” held me captivated. This question is about one small part of 216: the practical implications for ordinary patients that may follow from the email discussed from Harry. In particular, Harry’s comments on present serology testing limitations and his question about where to search for molecules which an anti-viral drug could target. The excerpt begins at minute 59:27.
Because I think staff at my doctor’s office might enjoy the excerpt, I want to be sure I grasp the main points in it. Besides offering insight possibly new to them, maybe this excerpt will also alert them to the practical benefits of TWiM.
(I’ve discovered the FFMPEG app and now can create appealingly short snippets to share in personal correspondence and give a taste of various microbe.tv podcasts, always with a link and attribution, of course. If that’s not okay, let me know. I would not publicly post such an excerpt; in fact, I don’t publish any articles.)
Back to Harry’s email: I may have misunderstood – never studied microbiology – but it sounds like present serology tests are barely useful. They can’t be relied upon by medical staff to accurately evaluate a patient’s stage of infection or post-infection. From that I infer that patients should be skeptical of them, too, especially of a negative result. Was that your takeaway from his comments?
IgM assays are especially unhelpful due to low specificity. Even IgG test results, which have much better specificity, must be interpreted with many caveats. Is the right antigen being tested? The false negative rate for IgG assays is high, so a natural question is, What’s the false negative rate for a given serologic test? Has enough time elapsed for the assay to detect latent presence of antibody – I guess he means that the assay must be allowed to culture for weeks?
From all that, it appears that Harry in late April did not see a serologic test that could tell one very much. I wonder if that still holds for the commonly given serologic tests in the US at this time?
Also, Harry linked to Australia Public Health Lab Network (PHLN) point-of-care testing guidelines from March 20. Quote: “PHLN recommends that mass surveys of immunity to retrospectively determine the true prevalence of infection should be done with enzyme immunoassays and not lateral flow devices.“ Is the upshot that until we learn otherwise, patients should be seeking an EIA or ELISA based serology test? It sounds like having an answer to this question would help patients get more quickly to a trustworthy test result. In TWiM 216 you seemed to allude to this, but it would be nice to hear you discuss in a manner that is clear to laypersons who don’t work in labs.
Link to Aussie PHLN guidelines: https://www.health.gov.au/resources/publications/phln-statement-on-point-of-care-serology-testing-for-sars-cov-2-the-virus-that-causes-covid-19