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There are currently controversies regarding the role of HLA matching in kidney transplantation, concerning whether it should be a determinant in organ allocation and survival. The study by Gramlick in Australia found that transplants that took HLA matching into account had better graft function and recipient survival compared to non-matching transplants (1). However, these results are attributed to the shorter dialysis time in the matching group, and when adjusting for this variable, the effect on recipient survival was not significant (p=0.07). Advances in the assessment of immunological risk and treatment allow for favorable outcomes in both groups, suggesting that the HLA match may be losing clinical significance in the modern era of transplantation.
Taking HLA matching into account can lead to inequity in organ allocation as recipients from racial minority groups are less likely to achieve a favorable match due to HLA polymorphism, resulting in longer waiting times for transplantation. In our study, we evaluated patient and graft survival in patients with HLA mismatch 5-6 and compared it to patients with better compatibility, with the purpose of analyzing whether limiting transplantation in this group of patients is appropriate or not.
A survival analysis was conducted based on a prospective cohort of kidney transplant recipients at Hospital Universitario San Ignacio in Bogotá, Colombia. Overall and graft survival functions were compared up to 10 years of follow-up according to the degree of HLA compatibility using the Log Rank statistical method and a Cox proportional hazards model, controlled for multiple confounding factors.
375 patients were included, 59 with HLA mismatch 5-6. The median follow-up was 84.3 months. Overall, 10-year survival was 84.0% (HLA mismatch 0-2), 80.8% (HLA mismatch 3-4), and 79.7% (HLA mismatch 5-6). 5 years overall survival was 91.0%, 87.7% and 84.4% respectively. 10 years death-censored graft survival was 92.1% (HLA mismatch 0-2), 88.2% (HLA mismatch 3-4) and 83.1% (HLA mismatch 5-6). Five years graft survival was 96.5%, 94.1% and 88.2%. No significant differences were found in overall survival (log rank p=0.661) or in graft survival (p=0.229). The Cox regression model did not show significant differences in mortality, but in graft survival functions between HLA mismatch 5-6 vs. HLA mismatch 0-2 (HR=2.7; 95% CI 1.08,6.94; p=0.032). No significant differences in graft survival were found between those with HLA mismatch 5-6 vs. HLA mismatch 3-4 (log rank p 0.430). We could attribute our results to the use of optimal immunosuppression therapy, better management of comorbidities such as diabetes, hypertension, dyslipidemia, having a virtual crossmatch negative for unacceptable antigens, and strict post-transplant follow-up
The degree of HLA mismatch does not result in a significant difference in the overall and graft survival, suggesting that kidney transplantation should not be limited in these patients. We recommend a review of kidney allocation policies worldwide to prevent inequities in patient care.