Panel-reactive antibody screening practices prior to heart transplantation

Evaluation of humoral sensitization, commonly determined by the panel-reactive antibody (PRA) screen, is accepted as an important part of pre-transplant assessment. A variety of definitions and approaches to sensitization have been described in the literature but no analyses of actual practice have been reported.

We sent surveys to 108 adult heart transplant program directors and 20 tissue-typing laboratories to obtain information about their approaches to PRA and crossmatch determination and management of sensitized patients.

Among 65 responding directors (60%), 63.1% were cardiologists and 36.9% surgeons. The most common threshold to consider PRA as positive is > or = 10%. Fifty-five of the respondents consider reactivity with T or B lymphocytes to be significant, whereas 34% consider only T-lymphocyte reactivity. Timing of PRA determination varies considerably among programs. Conversion to positive PRA results in more frequent PRA assessments and often therapy aimed to decrease the degree of sensitization. The most commonly utilized approaches are administration of immunoglobulin and plasmapheresis. The complement-dependent cytotoxicity (CDC) assay is the most commonly used method for PRA determination, but other techniques including flow cytometry and enzyme-linked immunosorbent assay (ELISA) are also used. Crossmatches are performed utilizing CDC and flow cytometry methods. Many laboratories employ more than one technique.

PRA screening, crossmatch determinations and management of sensitized patients vary considerably from center to center. Uncertainty exists about the importance of PRA values, threshold for treatment and clinical implications of sensitization. Important questions about the impact of sensitization on outcomes following heart transplantation may not be resolved until the measurement and management of sensitization becomes more uniform.