[PCR for COVID in the transplant protocol]

Background

Since the beginning of the SARS-CoV-2 pandemic, identifying the COVID-19 pathophysiology not only has been addressed to applying diagnostic tests or preventing through vaccines, but also to the timely detection, especially of patients in risk groups such as those in transplants areas (renal, hematology, etcetera). In the case of these patients, using RT-PCR tests avoids putting them at risk by subjecting them to states of immunosuppression that could aggravate their situation if they were faced with an onset of a COVID-19 infection.

Objective

To present the results of patients of a transplant unit tested for SARS-CoV-2.

Material and methods

Descriptive, observational, cross-sectional, and retrolective study. Data of results of RT-PCR tests of patients who underwent transplantation from June 2021 to April 2022 in a third level hospital were collected.

Results

755 tests were done to patients who underwent transplantation. 384 (50.8%) were women. Out of all patients, only 73 (9.7%) were positive to SARS-CoV-2.

Conclusions

Implementing RT-PCR tests as a transplant protocol to detect SARS-CoV-2 prevents fatal complications due to COVID infection to donors and receptors.

The immunogenetic diversity of the HLA system in Mexico correlates with underlying population genetic structure

We studied HLA class I (HLA-A, -B) and class II (HLA-DRB1, -DQB1) allele groups and alleles by PCR-SSP based typing in a total of 15,318 mixed ancestry Mexicans from all the states of the country divided into 78 sample sets, providing information regarding allelic and haplotypic frequencies and their linkage disequilibrium, as well as admixture estimates and genetic substructure. We identified the presence of 4268 unique HLA extended haplotypes across Mexico and find that the ten most frequent (HF > 1%) HLA haplotypes with significant linkage disequilibrium (Δ'≥0.1) in Mexico (accounting for 20% of the haplotypic diversity of the country) are of primarily Native American ancestry (A*02~B*39~DRB1*04~DQB1*03:02, A*02~B*35~DRB1*08~DQB1*04, A*68~B*39~DRB1*04~DQB1*03:02, A*02~B*35~DRB1*04~DQB1*03:02, A*24~B*39~DRB1*14~DQB1*03:01, A*24~B*35~DRB1*04~DQB1*03:02, A*24~B*39~DRB1*04~DQB1*03:02, A*02~B*40:02~DRB1*04~DQB1*03:02, A*68~B*35~DRB1*04~DQB1*03:02, A*02~B*15:01~DRB1*04~DQB1*03:02). Admixture estimates obtained by a maximum likelihood method using HLA-A/-B/-DRB1 as genetic estimators revealed that the main genetic components in Mexico as a whole are Native American (ranging from 37.8% in the northern part of the country to 81.5% in the southeastern region) and European (ranging from 11.5% in the southeast to 62.6% in northern Mexico). African admixture ranged from 0.0 to 12.7% not following any specific pattern. We were able to detect three major immunogenetic clusters correlating with genetic diversity and differential admixture within Mexico: North, Central and Southeast, which is in accordance with previous reports using genome-wide data. Our findings provide insights into the population immunogenetic substructure of the whole country and add to the knowledge of mixed ancestry Latin American population genetics, important for disease association studies, detection of demographic signatures on population variation and improved allocation of public health resources.