Objective To audit the 1990 International Society for Heart and Lung Transplantation cardiac rejection criteria and to evaluate the impact on classification and clinical outcomes of a modification in which grade 2 is abolished and grades 1A and 1B are amalgamated into a single “grade 1.”

Results The relative ratios of potentially significant rejection (grade 3A, 3B, 4) remained constant over the entire study in groups 1.1, 1.2, and 2. A 50% reduction in grade 2 biopsy reporting was noted comparing early and late parts of group 1. At subsequent review of the group 1 grade 2 biopsies, 97% could be reassigned to grades 0 or 1 in the modified scheme, with the majority of these diagnoses reflecting Quilty effect/biopsy site reactions. Two cases (3%) of the 77 grade 2 biopsies were regraded as grade 3A rejection, with both occurring within three months of transplantation. None of the grade 1B biopsies had high grade cardiac rejection on review, most of these biopsies similarly showing pronounced Quilty effect and biopsy site reactions. Actuarial survival at one year rose from 86% to 90% during the study, with freedom from 3A rejection remaining unchanged at 80%.

Conclusions The original working formulation produces consistent grading except at grade 2, which is judged to be a misnomer resulting from Quilty effect and other non-rejection phenomena. While acceptable standardisation can be achieved with the 1990 scheme, the modified scheme has advantages in that it appears to encourage clear discrimination between significant and non-significant cardiac rejection. Overall, elimination of grade 2 did not produce an increase in higher grades of cardiac rejection, and thus the value of this diagnostic grade is questioned.