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My understanding is the commercial antibody test has specificity issues. California dept public health is working with several partners to get an appropriate test. 1
Remember, sensitivity and specificity matter as does prevalence in population tested. If community prevalence is 6% then test with sensitivity of 95%/specificity 98% has + predictive value of only 75%. If prevalence is 10% then it is 84%. 2
So it seems like the commercial antibody test for the general public who have not tested positive by PCR could cause a lot of confusion and lead some people to think they are protected. Also, we don’t even know what level of protection antibodies confer or for how long. 3.
For people wanting to know a little more about sensitivity, specificity and prevalence this link seems pretty good. 4 https://geekymedics.com/sensitivity-specificity-ppv-and-npv/#Background
I’m a big fan of the California Department of Public Health and when they say the antibody test is ready for the public I will listen. 5
I understand the confusion when some hospitals are testing people for antibodies to donate plasma, but that is not the commercial test that is available. 6
