Seventy-five years of service: an overview of the College of American Pathologists' proficiency testing program in histocompatibility and identity testing

Abstract

The Histocompatibility and Identity Testing Committee offers an overview of the College of American Pathologists' (CAP) Proficiency Testing (PT) program, commemorating its significant 75th anniversary in 2024. The CAP PT program has undergone significant growth and evolution over the years, ultimately achieving Centers for Medicare and Medicaid Services approval. In 1979, CAP's partnership with the American Association for Clinical Histocompatibility Testing marked a pivotal moment, leading to the creation of the first proficiency testing survey in 1980. This laid the foundation for various PT programs managed by the CAP Histocompatibility and Identity Testing Committee, including HLA antibody testing, HLA molecular typing, engraftment monitoring, parentage/relationship testing, HLA disease associations and drug risk, and HLA-B27 typing. Each program's distinctive considerations, grading methodologies, and future prospects are detailed here, highlighting the continual evolution of histocompatibility and identity testing PT to support emerging technologies and evolving laboratory practices in the field.

Keywords: College of American Pathologists (CAP); HLA antibody testing; HLA molecular typing; HLA-B27; disease association; histocompatibility and identity testing committee; monitoring engraftment; proficiency testing.

FIGURE 1

Electropherograms demonstrating stutter Electropherograms for the D21S11 short tandem repeat (STR) marker. The top panel is the electropherogram for the donor while the bottom panel is the electropherogram for the recipient pre-transplantation. The middle panel is the electropherogram for the recipient post-transplantation (allele, area = peak area, size = allele size). The post-transplant sample demonstrates that the recipient alleles (allele 28 and allele 30) are in the stutter of the donor alleles (allele 29 and allele 31). The presence of stutter peaks (represented by the smaller solid peaks) introduces complexity when attempting to interpret the percentage of donor and recipient contributions. This challenge arises due to the overlapping nature of recipient and donor markers. Typically, markers exhibiting stutter peaks are not considered informative for determining percent chimerism. Nevertheless, it is possible to utilize these markers if specific calculations are employed to accommodate for the average percent stutter associated with the particular marker in question.