Rationale for surrogate testing to detect non-A, non-B hepatitis.

NANB hepatitis was initially recognized in 1975 and 13 years later, the exact etiology of this presumed viral disease remains uncertain. The acute illness is relatively mild with only about 25% of patients becoming icteric. Nevertheless, at least one half of the patients have evidence of chronic infection, and, as recently recognized, 10% to 20% develop severe liver disease. Because approximately 2% of patients who receive transfusions and whose underlying medical condition permits long term follow-up develop posttransfusion hepatitis, procedures for reducing this risk are considered prudent. Unfortunately specific tests for detecting NANB hepatitis are not available, and it is unlikely that such tests will be available in the near future. Hence, testing by surrogate or nonspecific tests (ALT and anti-HBc) were recommended because evidence from two studies conducted during the 1970s showed these tests identify some donors thought to transmit the infection. However, randomized, controlled prospective studies to determine whether these tests will, in fact, reduce NANB posttransfusion hepatitis were not performed. By the mid-1980s it was apparent these studies would not be performed nor were studies to determine the incidence of NANB posttransfusion hepatitis in the post-AIDS screening era likely to be initiated. Therefore, surrogate testing, as the best available method for reducing posttransfusion hepatitis, was implemented in the United States in 1986-87.