blueash |
04-12-2020 11:55 AM |
There are antibody tests available, on a very limited basis. Their accuracy is good not great. No commercial labs are now doing them so telling your doctor you want an antibody test is not going to get you one, yet.
Chalkboard time:
When you become ill and begin to mount an antibody defense the first significant response is from a subclass of immuno globin named IgM. This rapidly appearing protein has the typical upward then downward curve over time. For each particular germ, the timing of when the IgM appears, peaks, and disappears is different. Studies are ongoing to try to learn the shape of that curve. That information will be essential if you want to have a clue as to when someone was infected.
More slowly your body makes IgG which is your long term immune protection. IgG is not there as quickly as IgM, but in most diseases [there are always zebras] it is either very long lasting or hopefully forever.
The antibody tests being developed can be IgM tests, which are useful mostly for have you became ill very recently, or IgG tests which are useful for if you became ill weeks to months to years ago. Of course you could get tested both for IgM and IgG. Some tests will do that. Also a test can be yes/no. Is there detectable IgM, yes or no as opposed to what is the quantity of IgM. Similarly for IgG. In a yes/no test the manufacturer has to pick a cut off to read as positive. Is it hot out today? 79 degrees no 80 degrees yes. So it can be a bit arbitrary. [ see sensitivity, specificity, positive predictive value, negative predictive value...] If I say I will call any day "hot" if my thermometer read 50 or more, my results will identify 100% of hot days, but will also call days hot that were not hot. OTOH if I say I will call it hot if my thermometer reads 95, I will not errantly call it hot if it wasn't, but I will miss days that actually were hot. Picking the best cut off is always a compromise between these kinds of errors.
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