Rationale, Design, and the Baseline Characteristics of the RHDGen (The Genetics of Rheumatic Heart Disease) Network Study

BACKGROUND: The genetics of rheumatic heart disease (RHDGen) Network was developed to assist the discovery and validation of genetic variations and biomarkers of risk for rheumatic heart disease (RHD) in continental Africans, as a part of the global fight to control and eradicate rheumatic fever/RHD. Thus, we describe the rationale and design of the RHDGen study, comprising participants from 8 African countries. METHODS: RHDGen screened potential participants using echocardiography, thereafter enrolling RHD cases and ethnically-matched controls for whom case characteristics were documented. Biological samples were collected for conducting genetic analyses, including a discovery case-control genome-wide association study (GWAS) and a replication trio family study. Additional biological samples were also collected, and processed, for the measurement of biomarker analytes and the biomarker analyses are underway. RESULTS: Participants were enrolled into RHDGen between December 2012 and March 2018. For GWAS, 2548 RHD cases and 2261 controls (3301 women [69%]; mean age [SD], 37 [16.3] years) were available. RHD cases were predominantly Black (66%), Admixed (24%), and other ethnicities (10%). Among RHD cases, 34% were asymptomatic, 26% had prior valve surgery, and 23% had atrial fibrillation. The trio family replication arm included 116 RHD trio probands and 232 parents. CONCLUSIONS: RHDGen presents a rare opportunity to identify relevant patterns of genetic factors and biomarkers in Africans that may be associated with differential RHD risk. Furthermore, the RHDGen Network provides a platform for further work on fully elucidating the causes and mechanisms associated with RHD susceptibility and development

A differential response to antihypertensive therapy in African men and women: Insights from the CREOLE Trial

Background: We sought to address the paucity of data to support the evidence-based management of hypertension to achieve optimal blood pressure (BP) control on a sex-specific basis in Africa. Methods: We undertook a post hoc analysis of the multicenter, randomized CREOLE (Comparison of Three Combination Therapies in Lowering Blood Pressure in Black Africans) Trial to test the hypothesis that there would be clinically important differences in office BP control between African men and women. We compared the BP levels of 397 and 238 hypertensive women (63%, 50.9 ± 10.5 years) and men (51.2 ± 11.3 years) from 10 sites across sub-Saharan Africa who completed baseline and 6-month profiling according to their randomly allocated antihypertensive treatment. Results: Overall, 442/635 (69.6%) participants achieved an office BP target of \u3c140/90 mm Hg at 6 months; comprising more women (286/72.0%) than men (156/65.5%) (adjusted odds ratio [OR] 1.59, 95% confidence interval [CI] 1.07–2.39; P = 0.023). Women randomized to amlodipine–hydrochlorothiazide (HCTZ) (adjusted OR 3.03, 95% CI 1.71–5.35; P \u3c 0.001) or amlodipine–perindopril (adjusted OR 2.62, 95% CI 1.49–4.58; P = 0.01) were more likely to achieve this target compared with perindopril–HCTZ. Among men, there were no equivalent treatment differences—amlodipine–HCTZ (OR 1.54, 95% CI 0.76–3.12; P = 0.23) or amlodipine–perindopril (OR 1.32, 95% CI 0.65–2.67; P = 0.44) vs. perindopril–HCTZ. Among the 613 participants (97%) with 24-hour ambulatory BP monitoring, women had significantly lower systolic (124.1 ± 18.1 vs. 127.3 ± 16.9; P = 0.028) and diastolic (72.7 ± 10.4 vs. 75.1 ± 10.5; P = 0.007) BP levels at 6 months compared with men. Conclusions: These data suggest clinically important differences in the therapeutic response to antihypertensive combination therapy among African women compared with African men

Association of Novel Locus With Rheumatic Heart Disease in Black African Individuals:Findings From the RHDGen Study

IMPORTANCE: Rheumatic heart disease (RHD), a sequela of rheumatic fever characterized by permanent heart valve damage, is the leading cause of cardiac surgery in Africa. However, its pathophysiologic characteristics and genetics are poorly understood. Understanding genetic susceptibility may aid in prevention, control, and interventions to eliminate RHD. OBJECTIVE: To identify common genetic loci associated with RHD susceptibility in Black African individuals. DESIGN, SETTING, AND PARTICIPANTS: This multicenter case-control genome-wide association study (GWAS), the Genetics of Rheumatic Heart Disease, examined more than 7 million genotyped and imputed single-nucleotide variations. The 4809 GWAS participants and 116 independent trio families were enrolled from 8 African countries between December 31, 2012, and March 31, 2018. All GWAS participants and trio probands were screened by use of echocardiography. Data analyses took place from May 15, 2017, until March 14, 2021. MAIN OUTCOMES AND MEASURES: Genetic associations with RHD. RESULTS: This study included 4809 African participants (2548 RHD cases and 2261 controls; 3301 women [69%]; mean [SD] age, 36.5 [16.3] years). The GWAS identified a single RHD risk locus, 11q24.1 (rs1219406 [odds ratio, 1.65; 95% CI, 1.48-1.82; P = 4.36 × 10(−8)]), which reached genome-wide significance in Black African individuals. Our meta-analysis of Black (n = 3179) and admixed (n = 1055) African individuals revealed several suggestive loci. The study also replicated a previously reported association in Pacific Islander individuals (rs11846409) at the immunoglobulin heavy chain locus, in the meta-analysis of Black and admixed African individuals (odds ratio, 1.16; 95% CI, 1.06-1.27; P = 1.19 × 10(−3)). The HLA (rs9272622) associations reported in Aboriginal Australian individuals could not be replicated. In support of the known polygenic architecture for RHD, overtransmission of a polygenic risk score from unaffected parents to affected probands was observed (polygenic transmission disequilibrium testing mean [SE], 0.27 [0.16] SDs; P = .04996), and the chip-based heritability was estimated to be high at 0.49 (SE = 0.12; P = 3.28 × 10(−5)) in Black African individuals. CONCLUSIONS AND RELEVANCE: This study revealed a novel candidate susceptibility locus exclusive to Black African individuals and an important heritable component to RHD susceptibility in African individuals