What does the COVID-19 antibody test result mean for me?

Executive summary

• Your test results could be impacted by the time between when you were infected and get the test
• You could get a positive result for other reasons besides COVID-19

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I spent the beginning of my career looking at research studies for healthcare interventions, including pharmaceuticals, diagnostics and devices. However, I have never been close to requiring the information for a personal decision. The COVID-19 pandemic has made this decision close for the mass, so I decided to take a look into the types of tests that one could get in New York City. The New York City website talks about the antibody test, but it mostly focused on providing the public information on where to get it and open times. The New York State website has information on antigen, antibody and molecular testing.

I read the FDA emergency use authorization for the New York State antibody test they developed and found the following notes interesting:

• Interpretation of results. On the fourth page, there is a table that shows what values were used to translate to categorical results of negative, indeterminate or positive.

• Cross-reactivity. Although there is only one on page 4-5, the West Nile virus sample came up positive and three others were indeterminate with the test.

• Clinical performance. On page six, there is a table showing the sensitivity increasing from 17.9% to 79.3% as the days from onset ranges increased (from less than 7 to greater than 20 days – there are five ranges). The results were from over six clinical studies totaling 753 subjects.

• Limitation. There could be false results for patients taking biotin supplements.

Based on these notes, if I got the antibody test I would like to know my value before the categorical result (to know if I’m borderline) and contextualize the test to when I may have been exposed (if I got a negative result but was potentially exposed less than 20 days ago I may question the result). If I’m also positive, I would consider if I could possibly have the West Nile virus and check if I have biotin in anything I take.