Controversies in transfusion medicine. Alanine aminotransferase screening of blood donors: Pro

In my opinion, independent, carefully conducted scientific studies indicate that an accurate, rapid, relatively sensitive, and inexpensive laboratory test substantially reduces the major long-term risk of blood transfusion in the United States; donor ALT has emerged as one of the most effective laboratory determinants for reducing the incidence of NANB PTH. Despite its nonspecificity and limited predictive value, ALT screening may prevent up to 30 percent of cases, one-half of which would progress to chronic liver disease and then possibly to cirrhosis and hepatocellular carcinoma. Blood donors appear to understand and accept the testing rationale as a reasonable precaution. Admittedly, ALT screening is not a perfect solution. It has not been validated by prospective studies and probably nerver will be. Determination of the proper cutoff value remains controversial. However, the risk of PTH progresses with increasing ALT levels, so that the real issue is not whether to test, but how best to configure the test to exclude the fewest false-positive donors while detecting the most true-positive donors. It is undesirable and expensive to discard safe units of blood, but the primary responsibility of blood collectors is to ensure an adequate supply of safe components. Some still consider the ALT assay technically too demanding for routine use. However, technical concerns regarding performance and interpretation are not insurmountable, and both quality control and proficiency testing are being addressed at the national level. The assay is capable of great precision, and a system employing a national standard and single cutoff has already been described and tested with excellent results. Circumstances have changed since donor screening with ALT was widely implemented in 1986. More thorough screening and testing have eliminated many high-risk donors. Public expectations have changed as well. While it is neither reasonable nor responsible to promise the public blood transfusions without risk, neither is it prudent to propose any major change in management of the blood supply without compelling evidence that such a change will not impair transfusion safety. It is hard to defend discontinuing the ALT screen at this time, expecially when the costs of retaining it are minimal and the benefits clearly greater than those of screening for HTLV-I and for Treponema pallidum (in the United States) or HIV-2 (in West Germany). A first-generation assay specific for antibody to hepatitis C will probably be available within a year. If preliminary indications prove correct, it may prevent as much as 90 percent of NANB PTH. Test sensitivity will have to be improved or an antigen test will have to be developed to narrow the seronegative window. With this assay, we should be able to determine whether additional important NANB agents exist. Until then, if a burden of proof exists, it is to demonstrate that ALT screening no longer detects enough infectious donors to justify its retention. Before such data are available, policy makers should err on the side of recipient safety.