What happens if your donation tests positive?By Dr. Maria Simbra

PITTSBURGH (KDKA) — Blood services provider Vitalant has been testing all donated blood for coronavirus antibodies since June.

What happens if your donation tests positive? That is, it has evidence of an immune system reaction to the coronavirus spike protein.

“These donors, as a low prevalence population, have a number of false positives sprinkled in there just due to the nature of the test,” says Dr. Ralph R. Vassallo, executive vice president and chief medical & scientific officer at Vitalant.

Vitalant knows this because on Aug. 31, it introduced a second test on these samples. It checks for antibodies to another part of the coronavirus — the protein shell. Turns out, 10 percent of these positives on the first test, which shows you’ve had the illness in the past, are negative on the second test.

Donors are only notified if this second test is positive. But not quite yet.

“On Sept. 19 is when our computer system will be fully configured to identify these individuals,” says Dr. Vassallo. “Then we reach out to the donor and say, ‘Hey, would you consider plasmapheresis?'”

That’s the process for extracting plasma, the antibody-rich part of the blood. It’s more involved than a routine blood donation and takes about an hour. This convalescent plasma is given to people in the hospital who are sick with COVID-19.

And the amount of antibody varies donor to donor.

“We think, of course, asymptomatic and mildly symptomatic infected people have lower antibody titers,” Dr. Vassallo says.

The FDA’s emergency use authorization for convalescent plasma fully goes into effect on Dec. 1. The bags will have to be labeled as containing high or low levels of antibodies. The studies to date do not answer the best dose or best timing, but recipients will most likely get two bags of low antibodies or one bag of high antibodies.

Dr. Maria Simbra