Report by H.H. Gunson titled Alanine Amino-Transferase (ALT) and Hepatitis B Core (Anti-HBc) Screening of blood donations Summary of Results. Discusses study of ALT levels on anti-HBc tests on blood donors, including factors affecting raised ALT levels; variability of assays; rejecting donors based on ALT levels; Difficult to link raised ALT and anti-HBc; and ALT identifying the window of infectivity prior to seroconversion. Table 1 Distribution of ALT values in blood donors; Table 2 Details of donor follow-up; Table 3 Factors associated with raised ALT; Table 4 Hepatitis risk factors; Table 5 Anti-HBc testing and the confirmatory assays.