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RATIONALE & OBJECTIVE: Almost 80% of individuals with chronic kidney disease (CKD) reside in low- and middle-income countries (LMICs) and are potentially underrepresented in randomized controlled clinical trials (RCTs). We assessed the global distribution of RCTs comparing pharmacological treatments for CKD over the past 2 decades, as well as the magnitude and evolution of participation by LMICs. STUDY DESIGN: Systematic review. SETTING & STUDY POPULATIONS: RCTs evaluating pharmacological interventions in adults with CKD. SELECTION CRITERIA FOR STUDIES: RCTs published between 2003-2023 and indexed in MEDLINE. DATA EXTRACTION: Each trial was reviewed and extracted independently by 2 investigators with disagreements settled by consensus or a third reviewer. ANALYTICAL APPROACH: RCT participation of World Bank-defined income groups and geographic regions were described, and the representation indices (RI) according to RCT participants and estimated CKD prevalences were calculated. RCTs were also categorized as global, regional, or national in scope. RESULTS: Among 7,760 identified studies, we included 1,366 RCTs conducted in 84 countries with 301,158 participants. National, regional, and global RCTs represented 85.4%, 3.5%, and 11.1% of studies, respectively. LMICs were included in 34.7% of RCTs. No RCTs included participants from low-income countries, and lower-middle-income countries participated in 13.2%. Of participants from RCTs with available information, 25.4% (n=64,843 of 255,237) were from LMICs. According to the RI, 6 LMICs were overrepresented (>1.25), 7 were adequately represented (0.75-1.25), and 26 were underrepresented (<0.75). Most global CKD RCTs (80.2%) included LMICs; however, LMIC participants constituted only 32.9% of the global trial population. We observed a positive trend in LMIC inclusion over time, rising from 22.9% (n=71of 310) in 2003-2007 to 45.5% (n=140of 308) in 2018-2023. LIMITATIONS: The use of an income-group dichotomy, exclusion of nonrandomized studies of intervention, and studies identified in 1 database. CONCLUSIONS: Despite an increase in participation over the past 2 decades, individuals with CKD from LMICs remain significantly underrepresented in RCTs. These findings suggest that increased efforts are warranted to increase LMIC representation in pharmacological CKD RCTs. PLAIN-LANGUAGE SUMMARY: Chronic kidney disease (CKD) substantially affects people from low- and middle-income countries (LMICs). However, the participation of these countries in randomized controlled trials (RCTs) remains uncertain. To assess the global distribution and representation of these countries in kidney disease research, we reviewed 1,366 CKD drug RCTs published from 2003-2023, conducted in 84 countries involving more than 300,000 participants. LMICs were included in approximately a third of these studies, with their participants making up approximately one-quarter of the total; lower-middle-income countries were poorly represented, and low-income countries were absent. LMICs constituted a third of participants in multinational RCTs. Most LMICs were underrepresented relative to the prevalence of CKD. We observed an increasing inclusion of LMICs, particularly in the last decade. Nonetheless, individuals with CKD from LMICs remain underrepresented in drug RCTs, suggesting that increased efforts are warranted to include representation of these populations in these studies.
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INTRODUCTION: The causal relationship between hyperparathyroidism and kidney graft dysfunction remains inconclusive. Applying Bradford-Hill's temporality and consistency causation principles, we assessed the effect of parathyroid hormone (iPTH) on graft histology and eGFR trajectory on kidney transplant recipients (KTRs) with normal time-zero graft biopsies. METHODS: Retrospective cohort study evaluating the effect of hyperparathyroidism on interstitial fibrosis and tubular atrophy (IF/TA) development in 1232 graft biopsies. Pre-transplant hyperparathyroidism was categorized by KDIGO or KDOQI criteria, and post-transplant hyperparathyroidism by iPTH >1× and >2× the URL 1 year after transplantation. RESULTS: We included 325 KTRs (56% female, age 38 ± 13 years, follow-up 4.2 years [IQR: 2.7-5.8]). Based on pre-transplant iPTH levels, 26% and 66% exceeded the KDIGO and KDOQI targets, respectively. There were no significant differences in the development of >25% IF/TA between KTRs with pre-transplant iPTH levels above and within target range according to KDIGO (53% vs. 62%, P = .16, HR.94 [95% CI:.67-1.32]) and KDOQI (60% vs. 60%, P = 1.0, HR 1.19 [95% CI:.88-1.60]) criteria. Similarly, there were no differences when using 1 year post-transplant iPTH cut-offs > 88 pg/mL (58% vs. 64%, P = .33) and > 176 pg/mL (55% vs. 62%, P = .19). After adjusting for confounders, no significant differences were observed in eGFR trajectories among the iPTH strata. CONCLUSION: In young KTRs who received a healthy graft, no association was found between increased pre- and post-transplant iPTH levels and graft dysfunction, as assessed histologically and through eGFR trajectory. The concept of hyperparathyroidism as a risk factor for graft dysfunction in recipients at low risk requires reevaluation.