Blood Donor Deferrals by Expert System.

Blood collection facilities have recently witnessed a substantial increase in the number of different tests used to detect infectious disease in donor populations. These facilities are also experiencing an increasingly stringent regulatory effort on the part of the Food and Drug Administration to determine the validity of the software used to handle this information. This report describes a precedence-based inference program (PRELOG) and a modular expert system used to determine a donor's suitability for continued donations (donor deferrals), and whether the donated unit can be released for transfusion. PRELOG accepts ternary logic input, in which test results are allowed to be positive, negative, or undetermined; and allows one to assign precedence values to the logic rules. These features enable programs to be written in a shorter, more error-resistant manner. A comparison between PRELOG and PROLOG is included, and the utility of this approach in producing and validating blood bank software is discussed.