Lower Sensitivity Antigen Tests Provide a Much More “Accurate” Answer About Infectivity than High Sensitivity RT-PCR Tests?

An insightful article on COVID-19 testing was authored by Mara G. Aspinall co-founder of the biomedical diagnostics program at Arizona State University’s College of Health Solutions. Published October 9th.  According to Aspinall, “PCR tests cost too much and take too long, too few will be tested and the results will arrive too late to act on them. Counterintuitively, less sensitive antigen tests are more effective at identifying those who could otherwise become super-spreaders.”

Even if a less accurate antigen test misses the early hours of infectivity, it will definitely catch all cases by later that first day and on all subsequent days of infectivity. Over the next five to 10 days as patients recover, viral load declines only slowly, so PCR continues to be positive throughout this period. This is a serious disadvantage because these PCR positive individuals are “false positives” in the sense they can no longer transmit the virus to others.

Counter intuitive conclusion. The “lower” sensitivity of antigen tests provides a much more “accurate” answer about infectivity than the “higher” sensitivity RT-PCR test.

Mara G. Aspinall co-founded the biomedical diagnostics program at Arizona State University’s College of Health Solutions, which is the first program dedicated entirely to diagnostics as an independent discipline. She is Managing Partner of BlueStone Venture Partners and CEO of the Health Catalysts Group, a research and consulting firm for new healthcare companies.

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