People who receive the notices should be tested for the diseases, even though the risk that anyone contracted a virus is small, said Dr. Darrell J. Triulzi, medical director of Central Blood Bank in Pittsburgh.
The notices are the latest phase of a federal Food & Drug Administration investigation into a New York laboratory that screened samples of blood donated to Pittsburgh, Chicago, New York and Memphis.
Six testers at the lab were found to have cut corners on quality control rules. Two of them were convicted on criminal charges of creating false records that showed blood samples had been tested.
The FDA ordered blood banks in the four cities to post public health notices in November 1998. In the Pittsburgh area, roughly 6,000 people who received transfusions from September 1991 to December 1996 had free screenings offered by Central Blood Bank.
The testing found several cases of disease, but none could be linked to donations.
The new notices are based on a recent FDA review of testing documents at the New York lab.
"This is based on information that was not present in November 1998," Triulzi said.
The latest analysis found that 4,540 Central Blood Bank donations most of which were transfused in the Pittsburgh area could have been improperly screened.
Most were found to be from people who have tested negatively for disease, but 1,379 transfusions came from donors who may have been tainted and could have slipped through the flawed screenings.