Distance from a Transplant Center and Getting Listed for a Transplant

A data pipeline for secure extraction and sharing of social determinants of health

OBJECTIVES

Linking neighborhood- and patient-level data provides valuable information about the influence of upstream social determinants of health (SDOH). However, sharing of these data across health systems presents challenges. We set out to develop a pipeline to acquire, deidentify, and share neighborhood-level SDOH data across multiple health systems.

METHODS

We created a pipeline centered around Decentralized Geomarker Assessment for Multi-Site Studies (DeGAUSS) that utilizes containerization to geocode patient addresses and obtain neighborhood-level SDOH variables. We compared DeGAUSS to a third-party vendor geocoding tool available at Duke Health using a cohort of adult patients referred for abdominal transplant from January 1, 2016, to December 31, 2022. We calculated Cohen's Kappa and percent disagreement at census block group and tract levels, and by Area Deprivation Index, urbanicity, and year.

RESULTS

The pipeline successfully generated SDOH data for 97.8% of addresses. There was high concordance between DeGAUSS and the vendor tool at the census block group (0.93) and tract levels (0.95). At the block group level, disagreement proportion differed by year and urbanicity, with larger disagreement in the rural category than in micropolitan and metropolitan categories (13%, 7%, 6.2%, respectively).

DISCUSSION AND CONCLUSION

We describe a novel pipeline that can facilitate the secure acquisition and sharing of neighborhood-level SDOH without sharing PHI. The pipeline can be scaled to include additional social, climate, and environmental variables, and can be extended to an unlimited number of health systems.

Use of Donor-derived Cell-free DNA to Inform Tapering of Immunosuppression Therapy in Kidney Transplant Recipients: An Observational Study

Background

Immunosuppression therapy (IST) is required for allograft survival but can cause significant adverse effects. Donor-derived cell-free DNA (dd-cfDNA) is a validated noninvasive biomarker for active rejection in kidney transplant (KTx). Evidence supporting dd-cfDNA testing use in IST management is limited.

Methods

In this single-center observational study, dd-cfDNA testing was performed in 21 KTx patients considered good candidates for mycophenolic acid (MPA) reduction. Patients with dd-cfDNA <1% at the first visit (enrollment) had their MPA dosage reduced; those with dd-cfDNA ≥1% had their MPA dosage maintained. Patients were monitored with dd-cfDNA for 6 additional visits.

Results

Of 21 patients enrolled in the study, 17 were considered low risk for rejection by dd-cfDNA and underwent MPA reduction; 4 patients were considered high risk for rejection by dd-cfDNA and had their initial MPA dosage maintained. Of the 4 patients considered high risk for rejection by dd-cfDNA, 1 experienced chronic allograft nephropathy and graft loss, and another received an indication biopsy that showed no evidence of rejection. Of the 17 patients considered low risk for rejection by dd-cfDNA, none experienced allograft rejection. dd-cfDNA was used for surveillance in a 6-mo period following MPA reduction; no untoward results were noted.

Conclusions

This proof-of-concept study reports the use of dd-cfDNA to directly inform IST management in a cohort of KTx who were candidates for IST reduction.

Mettl14-mediated m6A modification enhances the function of Foxp3+ regulatory T cells and promotes allograft acceptance

N6-methyladenosine (m6A), the most prevalent form of internal mRNA modification, is extensively involved in Treg cells differentiation and function. However, the involvement of m6A in functional Treg cells for transplantation tolerance remains to be elucidated. By using an experimental transplantation mouse model, we found that m6A levels in Treg cells were altered during the induction of transplant tolerance by performing a dot blotting assay. Subsequently, we used the heterogenic Treg-specific Mettl14 knockout mice (Foxp3-Mettl14^f/+ cKO) to reduce METTL14 expression and performed islets allograft transplantation. Our result revealed that reduced expression of METTL14 prevented Treg cells expansion and promoted the infiltration of CD4⁺ and CD8⁺ T cells around the allograft, which led to rapid allograft rejection in Foxp3-Mettl14 ^f/+ cKO mice. The expression of regulatory cytokines including IL-10 and TGF-β was significantly decreased in Foxp3-Mettl14 ^f/+ cKO mice, and the suppressive function of Treg cells was also abrogated. In addition, an analysis of RNA-seq data revealed that the SOCS family (SOCS1, SOCS2 and SOCS3) is the subsequent signaling pathway affected by the METTL14 mediated m6A modification in Treg cells to modulate the suppressive function after transplantation. Taken together, our study showed for the first time that the METTL14-mediated m6A modification is essential for the suppressive function of Treg cells in transplantation and may serve as a regulatory element of Treg cell-based therapy in transplant medicine.

Toward telemedicine-compatible physical functioning assessments in kidney transplant candidates

Frailty is associated with adverse kidney transplant outcomes and can be assessed by subjective and objective metrics. There is increasing recognition of the value of metrics obtainable remotely. We compared the self‐reported SF‐36 physical functioning subscale score (SF‐36 PF) with in‐person physical performance tests (6‐min walk and sit‐to‐stand) in a prospective cohort of kidney transplant candidates. We assessed each metric's ability to predict time to the composite outcome of waitlist removal or death, censoring at transplant. We built time‐dependent receiver operating characteristic curves and calculated the area under the curve [AUC(t)] at 1 year, using bootstrapping for internal validation. In 199 patients followed for a median of 346 days, 41 reached the composite endpoint. Lower SF‐36 PF scores were associated with higher risk of waitlist removal/death, with every 10‐point decrease corresponding to a 16% increase in risk. All models showed an AUC(t) of 0.83–0.84 that did not contract substantially after internal validation. Among kidney transplant candidates, SF‐36 PF, obtainable remotely, can help to stratify the risk of waitlist removal or death, and may be used as a screening tool for poor physical functioning in ongoing candidate evaluation, particularly where travel, increasing patient volume, or other restrictions challenge in‐person assessment.