Screening the Blood Supply for West Nile Virus RNA by Nucleic Acid Amplification Testing

In 2003, nucleic acid amplification screening of 677,603 blood donations for West Nile virus with the use of “minipools” of 16 samples led to the identification of 1 positive donation for every 3703 analyzed (0.027 percent). In 2004, a strategy of testing individual donations in selected regions led to a 32 percent increase in the identification of donations with West Nile virus. This study shows that screening of pooled blood samples for West Nile virus prevented hundreds of infections but missed donations with a low level of viremia. West Nile virus, a mosquito-borne flavivirus, emerged as a cause of meningoencephalitis in the United States in 1999, and infections reached epidemic proportions in 2002. 1 , 2 In 2002, West Nile virus was shown to be transmissible by transfusion, when 23 cases were documented. 3 , 4 In late 2002, the Food and Drug Administration (FDA), U.S. blood-collecting organizations, and test-kit manufacturers accelerated programs to develop nucleic acid amplification tests to screen blood donors for West Nile viremia in an effort to implement such programs before the 2003 transmission season. 4 – 7 The resulting assays involved the testing of pools of 6 to 24 . . .