In Reply.—We would like to thank you for the opportunity to respond to the notes raised in the letter to the editor regarding Gandini et al,1  “A Retrospective Study on Human Leukocyte Antigen Types and Haplotypes in a South African Population,” and to clarify the methodology used. We would also like to thank the authors of the letter for their interest in our paper and for taking the time to express their concerns.

In their letter to the editor, the authors raised concerns with the human leukocyte antigen (HLA) types noted in Figure 1. The majority of the historic records examined were not performed or resulted by our laboratory, and several of the older records were handwritten. This may have resulted in transcription errors and reporting inconsistencies. We reported these records as accurately as possible. There was, however, some confusion between the serologic and genetic results. We have corrected the figure and resubmitted it in an erratum.1  Of note, this did not materially affect the results because these inaccuracies comprised a small percentage of the population. Where discrepancies were identified, the sample was excluded from the final analysis.

The authors noted that our haplotype analysis did not account for linkage disequilibrium. We did not have access to the software typically used for such analysis, but agree that it would be interesting to perform.

Regarding the virtual crossmatch analyses (Table 4), we agree with the authors that virtual crossmatches should be performed with antibodies and HLA typing results at the same resolution. The historic data used for this study were unfortunately HLA typed at a low 2-digit resolution whereas the single-antigen bead assays used provided 4-digit resolution, which was acknowledged as a limitation of the study.

We acknowledge that transplant algorithms comprise several factors and that an accurate assessment of the transplant program would need to assess all factors. Time on the waiting list, age, previous transplantations, and panel-reactive antibodies are some of the factors considered in the Johannesburg renal transplant program. Although HLA matching was previously considered as a criterion, the stated reason for its removal was the high degree of HLA heterogeneity in the South African multiethnic population and discrepancies between the donor and recipient populations that were thought potentially to impact certain populations negatively. A strength of this study is the sample population size, which allows the suggestion that HLA-matching reintroduction is unlikely to be feasible. We agree that further investigations should be conducted based on this recommendation as to the impact of HLA matching on the Johannesburg renal transplant program, which would require additional logistical support.

Ultimately, we agree with the authors that this study was limited by its retrospective nature and the low resolution of the HLA typing results. It does, however, provide guidance on including HLA matching in the criteria in a highly diverse, low-resource setting, after which more research can be conducted.

A retrospective study on human leukocyte antigen types and haplotypes in a South African population [published correction appears in Arch Pathol Lab Med. 2021;145(8):918]
Arch Pathol Lab Med. 2021;

The authors have no relevant financial interest in the products or companies described in this article.