However, while surging demand has proven a boon for the traders known as blood brokers who source this commodity, diagnostic companies say high prices for the blood of recovered Covid-19 patients are posing a hurdle to developing tests.

“We’ve had a terrible time trying to obtain positive specimens at a decent rate,” said Stefanie Lenart-Dallezotte, manager of business operations for San Diego-based Epitope Diagnostics Inc., which sells an antibody test for Covid-19. “I feel people are taking extreme advantage of the situation because they can, because there’s crazy demand.”

She said one broker quoted $1,000 for a one-milliliter sample of convalescent plasma, a term for the antibody-containing part of the blood from recovered patients.

Executives at other diagnostics companies say they have been quoted prices of several thousand dollars for one milliliter of plasma.