I have followed up with my colleagues. There is almost complete agreement between people who have positive swab tests and people who have positive western blot antibody tests. The problem with obtaining the exact accuracy of the western blot is that there is nothing better. A similar situation exists with PCR testing of lesions for herpes. For example, we know that PCR is about 75% more accurate than culture. And we know that the western blot picks up 8% of HSV-2 and 30% more of HSV one compared to the IgG test.
I have had 10 patients in my career who have positive swab tests and negative western blot antibody tests. Some of those patients had taken extended courses of antiviral medication prior to their initial diagnosis and that happened before we understood that taking daily antiviral medicine could interfere with the accuracy of the western blot. The blot looks for all 16 proteins associated with HSV two antibodies while the IgG test only looks for a single protein that is different between type one and type two. This extensive look at antibody proteins allows us to be much more accurate with the blot and more sensitive by a lot. I think that’s the best information that I can give you at this point.
The 99+ sensitivity of Western Blot comes from Dr. Lawrence Corey, Professor of medicine at the University of Washington and former head of the Fred Hutchison cancer Institute and world renowned herpes expert.