The researchers, who enrolled about 1,600 gay and bisexual men in eight metropolitan areas, are hoping to identify a set of screening questions that can differentiate men who are more likely to have recently acquired H.I.V. from those who are less likely to have recently contracted the virus.

Participants in the project, known as the ADVANCE study, answered a variety of questions about their recent, risk-related behaviors, such as whether they had any new sexual partners or were taking pre-exposure prophylactic drugs, known as PrEP, that reduce the risk of H.I.V. infection, said Brian Custer, director of Vitalant Research Institute and principal investigator of the study.

The participants’ blood was also tested for H.I.V. and the antiretroviral drugs used in PrEP.

The researchers have already shared an interim analysis with the F.D.A. and should have the final results ready before the end of the year, Dr. Custer said. He declined to provide more information about the preliminary findings, citing a confidentiality agreement with the F.D.A., but said that he expected the results to be informative for the agency.

“I really am confident that we have important information for the F.D.A. to be able to consider what an individual, risk-based approach to donor selection might look like,” he said.

Susan Stramer, vice president for scientific affairs for the American Red Cross, said in a statement that the study was meant “to make blood donation a more inclusive process while maintaining the safety of the blood supply.”

“While we have not been notified by the F.D.A. concerning policy changes at this time, the Red Cross looks forward to a future in which donation eligibility is not based on sexual orientation, and more healthy individuals can give blood to help patients in need,” she said.

The current blood shortage is tracked daily by America’s Blood Centers, the trade association for 59 community facilities. On Wednesday, about a quarter of the centers, or 16, had less than a day’s supply on hand.