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. 2024 Nov 14;143(1):7–14. doi: 10.1001/jamaophthalmol.2024.4784

Performance of Polygenic Risk Scores for Primary Open-Angle Glaucoma in Populations of African Descent

Jennifer M Chang-Wolf 1,2,3, Tyler G Kinzy 4,5,6,7,8, Sjoerd J Driessen 1,9, Lauren A Cruz 4,5, Sudha K Iyengar 4,5,6, Neal S Peachey 6,10,11, Tin Aung 12, Chiea Chuen Khor 13, Susan E Williams 14, Michele Ramsay 15, Olusola Olawoye 16, Adeyinka Ashaye 16, Caroline C W Klaver 1,9,17,18, Michael A Hauser 2,3,12, Alberta A H J Thiadens 1,9, Jessica N Cooke Bailey 4,5,6,7,8, Pieter W M Bonnemaijer 1,9,19,, for the for the for the Genetics in Glaucoma Patients of African Descent (GIGA) Study Group; Genetics of Glaucoma in People of African Descent (GGLAD) Study Group; Million Veteran Program (MVP)
PMCID: PMC11565374  PMID: 39541127

This cross-sectional study investigates how published polygenic risk scores for primary open-angle glaucoma (POAG) perform in groups with African ancestry compared with European ancestry.

Key Points

Question

How do published polygenic risk scores (PRSs) for primary open-angle glaucoma (POAG) perform in African-ancestry compared with European-ancestry groups?

Findings

In this cross-sectional study comparing 3 PRSs and including 11 673 cases and 66 432 controls across 7 ancestral groups, modest odds ratio increases were detected for the highest POAG risk quintile in Tanzanians, South Africans, Ghanaians, African Americans, and Europeans. However, overall predictive performance remains limited for African-ancestry compared with European-ancestry groups in terms of area under the curve and coefficient of determination.

Meaning

Results suggest that despite some improvements in POAG risk stratification among African-ancestry groups, this study underscores the need for further research to develop more accurate risk prediction models tailored to diverse populations for equitable health care outcomes.

Abstract

Importance

Primary open-angle glaucoma (POAG) polygenic risk scores (PRSs) continue to be evaluated in primarily European-ancestry populations despite higher prevalence and worse outcomes in African-ancestry populations.

Objective

To evaluate how established POAG PRSs perform in African-ancestry samples from the Genetics in Glaucoma Patients of African Descent (GIGA), Genetics of Glaucoma in Individuals of African Descent (GGLAD), and Million Veteran Program (MVP) datasets and compare these with European-ancestry samples.

Design, Setting, and Participants

This was a multicenter, cross-sectional study of POAG cases and controls from Tanzania, South Africa, Nigeria, Ghana, and the US. Included were individuals of African descent from South Africa and Tanzania from the GIGA dataset; individuals of African descent from Ghana, Nigeria, and the US from the GGLAD dataset; and individuals of African or European descent from the US in the MVP dataset. Data were analyzed from January 2022 to July 2023.

Exposures

Three PRSs derived from large meta-analyses of European and Asian populations, namely Gharahkhani et al (Gharahkhani PRS), Han et al (Han PRS), and Craig et al (Craig PRS).

Main Outcomes and Measures

Odds ratios (ORs) for POAG risk stratification comparing the highest and lowest quintiles; area under the receiver operating characteristic curve (AUROC), and liability coefficient of determination (R2) for the addition of PRS to a baseline of age, sex, and first 5 principal components.

Results

A total of 11 673 cases and 66 432 controls were included in this study across 7 ancestral groups. Mean (SD) age of the total participants was 76.9 (8.7) years, with 74 304 males (95.1%). The following were included in each dataset: GIGA (663 cases, 476 controls), GGLAD (1471 cases, 1482 controls), and MVP (9559 cases, 64 474 controls). Increases in ORs were found for the highest POAG risk quintile ranging from an OR of 1.68 (95% CI, 1.17-2.43) in Ghanaians to 7.05 (95% CI, 2.73-19.6) in the South African multiple ancestry group (which derives from at least 5 distinct ancestral groups: Khoisan, Bantus, Europeans, Indians, and Southeast Asians) with the Gharahkhani PRS. The Han PRS showed OR increases for the highest POAG risk quintile ranging from 2.27 (95% CI, 1.49-3.47) in African American individuals in the GGLAD dataset to 7.24 (95% CI, 6.47-8.12) in Europeans. The Craig PRS predicted OR increases in the highest quintile for all groups ranging from 1.51 (95% CI, 1.05-2.18) in Ghanaians to 6.31 (95% CI, 5.67-7.04) in Europeans. However, AUROC and R2 increases above baseline were lower for all African-ancestry compared with European-ancestry groups in the 3 tested PRSs.

Conclusions and Relevance

In this cross-sectional study, despite some improvements in OR-based risk stratification using the Gharahkhani PRSs, Han PRSs, and Craig PRSs, consistently lower improvements in AUROC and R2 for African-ancestry compared with European-ancestry groups highlight the need for risk prediction models tailored to diverse populations.

Introduction

Disproportionately affecting those of African ancestry, primary open-angle glaucoma (POAG) is a leading cause of irreversible blindness worldwide and is projected to become more prevalent in the coming decades.1,2,3 POAG affected an estimated 76 million people globally in 2020 and is projected to affect nearly 120 million by 2040, making it a significant cause of irreversible blindness.4,5,6,7 People of African descent face a higher risk, with up to 7 times the likelihood of developing POAG and experiencing blindness 4 times more frequently than those of European descent.8,9 Risk stratification based on clinical and demographic data has long been used to aid patient care, which enables the identification of patients with high-risk POAG for more frequent follow-up or more aggressive clinical management.10,11,12,13 Adding genetic data in the form of polygenic risk scores (PRSs) further improves risk stratification.14

Despite the disproportionate impact on individuals of African ancestry, genetic studies on POAG have focused on European and Asian populations, leaving a gap in understanding the genetic factors in African ancestral groups.15,16,17,18 Recent genomic research advancements allow genetic data to enhance disease risk prediction. PRSs integrate variants from genome-wide association studies (GWAS) to predict disease risk. However, the construction of these PRSs currently relies heavily on data derived from European populations, raising concerns about their applicability and transferability to other populations with higher incidences of the target diseases.16,19,20,21,22

PRS approaches have performed well in POAG, predicting advanced glaucoma risk and influencing treatment decisions.23,24,25 Importantly, these PRSs were constructed from and applied to population samples that were primarily European and Asian and are thus potentially more reflective of the genetic architecture of those groups. In this study, we evaluated the performance of these tools for their ability to stratify POAG risk in individuals of African ancestry from South Africa, Tanzania, Ghana, Nigeria, and the US.

Methods

The Genetics in Glaucoma Patients of African Descent (GIGA) study, the Genetics of Glaucoma in People of African Descent (GGLAD) study, and the Million Veteran Program (MVP) adhered to the tenets of the Declaration of Helsinki, received ethical approval from the local institutional review boards, and obtained informed consent from all participants with no stipend or other incentive to participate. Only complete cases with age, sex, genotype, and phenotype data were included. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guidelines.26

Study Population

GIGA is a multicenter POAG case-control study of individuals from the Groote Schuur Hospital (Cape Town, South Africa), Muhimbili National Hospital, and CCBRT Disability Hospital (Dar es Salaam, Tanzania).27 The GIGA study included Tanzanians, Black South African people, and a group of individuals of multiple ancestries, which derives from at least 5 distinct ancestral groups: Khoisan, Bantus, Europeans, Indians, and Southeast Asians and for whom we use the term South African multiple ancestry.28 Participants from the GGLAD discovery dataset included individuals of African descent recruited from Ghana (Lions International Eye Centre and Korle-Bu Teaching Hospital), Nigeria (University of Ibadan, University of Nigeria, and Nigerian Navy Reference Hospital), and North Carolina in the US (Duke University, Durham, North Carolina).29,30,31 The MVP is a national research program sponsored by the Department of Veterans Affairs (VA) Office of Research and Development that includes health, genetic, and lifestyle information from 1 million US military Veterans who consented to participate in an observational cohort study and mega biobank. The genetic ancestry of over 450 000 MVP individuals with available genome-wide data was determined using the harmonized ancestry and race/ethnicity algorithm.32,33

Genotyped data from the GIGA and GGLAD study groups were imputed to 1000 Genomes (1000G) phase 3, version 5.34 MVP samples were imputed on either the 1000G phase 3, version 5, reference panel or the African Genome Resource (not publicly available), which comprises all 1000G samples with an additional 2000 samples from Uganda and 100 samples from each of 5 populations in Ethiopia, Egypt, Namibia (Nama/Khoesan), and South Africa (Zulu).32,35

POAG Definition

GIGA POAG cases met International Society for Geographical and Epidemiological Ophthalmology classification categories 1 or 2, defined by a definite visual field defect and vertical cup disc ratio (VCDR) of greater than or equal to 0.7 or greater than 0.8 without visual field testing.36 Cases had an open angle on gonioscopy and onset age older than 35 years. Controls underwent similar assessments and were characterized by no glaucoma signs or family history, intraocular pressure (IOP) less than or equal to 21 mm Hg, VCDR less than 0.5, VCDR intereye asymmetry less than 0.2, and age older than 55 years.27,30,31,37 The GGLAD POAG definition included the presence of glaucomatous optic neuropathy characterized by loss of neuroretinal rim, VCDR greater than 0.7, intereye asymmetry greater than 0.2, and glaucoma-associated notching. Control samples were recruited from hospitals or the general population, with hospital-based controls being older than 40 years, free from (family history of) glaucoma or major eye diseases, IOP less than 21 mm Hg, open angles, healthy optic nerves, and normal visual fields. MVP cases and controls were defined by a computable phenotyping algorithm based on International Classification of Diseases–Clinical Modification codes, Current Procedural Terminology codes, and prescriptions in the VA computerized patient record system.38,39

Statistical Analysis

We tested 3 PRSs using weighted additive models where the imputed dosage of each risk allele (j) was multiplied by its calculated β (log odds ratio [OR]) and summed using PLINK2 to produce a score for each individual (i)40:

scorei = Σkj = 1 βjMij
  1. Gharahkhani PRS (k = 111): Based on 127 POAG-associated variants identified in the largest to date cross-ancestry single-trait POAG GWAS meta-analysis.41 To reduce potential bias due to inclusion of overlapping African ancestral data from the GIGA and GGLAD studies, we applied a fixed-effects inverse variance–weighted meta-analysis to 239 168 controls and 23 612 POAG cases of European or Asian descent. Without the African datasets, 115 single-nucleotide variants (SNVs) maintained genome-wide significance. The X chromosome was excluded because it was unavailable in some cohorts, leaving 111 autosomal SNVs.

  2. Given potential differences in linkage disequilibrium (LD) patterns, we developed a modified LD proxy PRS (k = 111) to incorporate SNV proxies while accounting for between-population LD variation. We analyzed SNV transferability via the local approach and evaluated a 500-kb window around each variant for SNVs with LD r2 greater than 0.2 (as defined by the 1000 Genomes African subset).27 We examined these for evidence of higher association in the African-only GWAS.41 Of these, 63 were nominally associated (P < .05), and the lead SNV was replaced with the local replacement SNV.

  3. Han PRS (k = 223): Based on multitrait GWAS meta-analysis of POAG, VCDR, and IOP that identified 263 novel POAG loci, of which we included 223 SNVs from the European discovery set that replicated in an independent 23andMe cohort in which the P value remained <.001 after Bonferroni correction to avoid inflation due to overlap between Asian and African samples.23

  4. Craig PRS (k = 2673): Based on a POAG PRS derived from 67 040 UK Biobank samples by combining multiple endophenotypes (eg, VCDR and IOP) in multivariate analysis and validating the 2673 SNVs with P ≤ .001 in independent European datasets.25

To investigate score value distributions across study groups, we plotted PRS densities standardized with a mean of 0 and an SD of 1 (eFigure 1 in Supplement 1). To account for potential nonlinear association and facilitate comparisons between different sample sizes, we constructed PRS quintiles. To adjust for confounding factors, we included age, sex, and the first 5 principal components (PCs) as covariates. For each quintile, we used a logistic regression model to estimate ORs of POAG risk and 95% CIs.

Aside from quintile stratification, we implemented logistic regression models of baseline alone (ie, age, sex, and 5 PCs) and with the addition of continuous PRS values. We examined the area under the receiver operating characteristic curve (AUROC) and used the DeLong test to compare area under the curve increases from the addition of PRS with the baseline models. We additionally evaluated the added value of continuous PRSs to baseline by determining increases in R2 coefficients of determination. We computed R2 on the liability scale to account for varying proportions of phenotypic variance explained by each PRS.42,43 Case/control ratios in this study ranged from 0.09 in the European American group to 0.70 in the South African Black group. We fixed disease prevalence at 2.4% for comparison, although prevalence may vary across ancestral groups.44 Data were analyzed from January 2022 to July 2023, using R statistical software, version 4.2.1 (R Foundation for Statistical Computing).

Results

Study Demographics for POAG Cases and Controls

A total of 11 673 cases and 66 432 controls were included in this study across 7 ancestral groups: Tanzanian (366 cases, 329 controls), South African multiple ancestry (179 cases, 96 controls), South African Black (118 cases, 51 controls), Nigerian (125 cases, 185 controls), Ghanaian (640 cases, 690 controls), African American (4627 cases, 6272 controls), and European American (5618 cases, 58 809 controls). The African American group comprised 2 subgroups: the GGLAD dataset (706 cases, 607 controls) and MVP dataset (3921 cases, 5665 controls). The following were included in each dataset: GIGA (663 cases, 476 controls), GGLAD (1471 cases, 1482 controls), and MVP (9559 cases, 64474 controls). Mean (SD) age of the total participants was 76.9 (8.7) years, with 3801 females (4.9%) and 74 304 males (95.1%). Study sample characteristics are presented in the Table. Sex proportions differed between cases and controls in the Tanzanian (female sex: 125 of 366 cases [34.2%], 172 of 329 controls [52.3%]; P = 2.1 × 10−6), South African Black (female sex: 62 of 118 cases [52.5%], 40 of 51 controls [78.4%]; P = 2.8 × 10−3), Nigerian (female sex: 48 of 125 cases [38.4%], 104 of 185 controls [56.2%]; P = 3.1 × 10−3), African American MVP (female sex: 216 of 3921 cases [5.5%], 171 of 5665 controls [3.0%]; P = 1.9 × 10−9), and European American (female sex: 211 of 5618 cases [8.7%], 1314 of 58 809 controls [2.2%]; P = 5.91 × 10−13) groups based on χ2 testing. The mean (SD) age differed between cases and controls in the South African Black (62.9 [10.7] years; P = 2 × 10−4), Tanzanian (64.8 [9.8] years; P = 3.4 × 10−6), Ghanaian (59.6 [11.1] years; P = 4.5 × 10−23), and African American GGLAD (61.3 [12.7] years; P = 8.1 × 10−94) as well as African American MVP (74.2 [7.9] years; P = 2.2 × 10−16) groups based on Welch t test.

Table. Demographic Summarya.

Variable GIGA GGLAD MVP
Tanzanian South African multiple ancestryb South African Black Nigerian Ghanaian African American African American European American
No. (%)
Total 695 275 169 310 1330 1313 9586 64 427
Cases 366 (52.7) 179 (65.1) 118 (69.8) 125 (40.3) 640 (48.1) 706 (53.8) 3921 (40.9) 5618 (8.7)
Controls 329 (47.3) 96 (34.9) 51 (30.2) 185 (59.7) 690 (51.9) 607 (46.2) 5665 (59.1) 58 809 (91.3)
Female sex, No. (%)
Cases 125 (34.2) 93 (52.0) 62 (52.5) 48 (38.4) 279 (43.6) 336 (47.6) 216 (5.5) 211 (3.8)
Controls 172 (52.3) 54 (56.3) 40 (78.4) 104 (56.2) 297 (43.0) 279 (46.0) 171 (3.0) 1314 (2.2)
Male sex, No. (%)
Cases 241 (65.8) 86 (48.0) 56 (47.5) 77 (61.6) 361 (56.4) 370 (52.4) 3705 (94.5) 5407 (96.2)
Controls 157 (47.7) 42 (43.8) 11 (21.6) 81 (43.8) 393 (56.9) 328 (54.0) 5494 (97.0) 57 495 (97.8)
P value (χ2 test) 2.1 × 10−6 .58 2.8 × 10−3 3.1 × 10−3 .88 .54 1.9 × 10−9 5.91 × 10−13
Age, mean (SD), y
Total 64.8 (9.8) 69.7 (10.0) 62.9 (10.7) 63.5 (11.5) 59.6 (11.1) 61.3 (12.7) 74.2 (7.9) 78.2 (7.6)
Cases 63.2 (11.0) 70.5 (11.0) 61.3 (11.5) 63.7 (11.5) 62.7 (12.4) 67.4 (12.3) 71.2 (9.5) 78.2 (7.6)
Controls 66.6 (8.1) 68.3 (7.7) 66.8 (7.2) 63.4 (11.5) 56.7 (9.0) 54.2 (9.0) 76.2 (6.7) 78.2 (7.4)
P value (Welch t test) 3.4 × 10−6 .06 2 × 10−4 .82 4.5 × 10−23 8.1 × 10−94 2.2 × 10−16 .47

Abbreviations: GGLAD, Genetics of Glaucoma in Individuals of African Descent; GIGA, Genetics in Glaucoma Patients of African Descent; MVP, Million Veteran Program.

a

The table presents information for the included population groups across different demographic variables.

b

The South African multiple ancestry group derives from at least 5 distinct ancestral groups: Khoisan, Bantus, Europeans, Indians, and Southeast Asians.

POAG Risk Stratification by PRS

We evaluated the performance of the 3 PRS in 8 study groups by comparing ORs categorized into quintiles, as illustrated in Figure 1 and detailed in eTable 1 in Supplement 1. The distribution of case proportions by quintile is visually depicted in eFigure 2 in Supplement 1. Figure 2 shows the increase in AUROC compared with the baseline model; detailed AUROC values are provided in eTable 2 in Supplement 1. Additionally, we examined R2 values on the liability scale to further characterize the predictive accuracy of the evaluated scores (eTable 3 in Supplement 1). Here, we present the results of these measures separately for each score.

Figure 1. Odds Ratios by Quintile.

Figure 1.

The odds ratios (log scale) of risk for primary open-angle glaucoma from logistic regression by quintile for each of 8 study groups are displayed using 3 polygenic risk score (PRS) types: Gharahkhani PRS (A), Han PRS (B), and Craig PRS (C). Odds ratios (on a log scale) and 95% CIs are presented, allowing for comparison of risk across quintiles within each risk score type. GGLAD indicates Genetics of Glaucoma in People of African Descent; MVP, Million Veteran Program.

Figure 2. Improvement in Area Under the Receiver Operating Characteristic (AUROC) Curve Adding a Polygenic Risk Score (PRS) to the Baseline Model by Population and PRS.

Figure 2.

The improvement of the AUROC of a model with the genetic risk score/PRS compared with a baseline model of sex, age, and 5 principal components is shown. The data are organized by population groups, including Tanzanian, South African multiple ancestry (which derives from at least 5 distinct ancestral groups: Khoisan, Bantus, Europeans, Indians, and Southeast Asians), South African Black, Nigerian, Ghanaian, African American (Genetics of Glaucoma in People of African Descent [GGLAD]), African American (Million Veteran Program [MVP]), and European. The heights of the bars reflect the AUROC increase values, and each bar is color-coded according to baseline vs values after addition of the Gharahkhani PRS (designated G), Han PRS (designated H), and Craig PRS (designated C) as indicated on the x-axis.

Gharahkhani PRS

Using the Gharahkhani PRS consisting of 111 SNVs, we observed an increase in the OR for POAG risk within the highest PRS quintile, compared with the lowest quintile across all groups except Nigerian (Figure 1). Relative to the European American group in this study (OR, 5.02; 95% CI, 4.54-5.57), the ORs within the highest quintile were increased but had wider CIs in the South African groups. Specifically, increases in ORs were found for the highest POAG risk quintile ranging from an OR of 1.68 (95% CI, 1.17-2.43) in Ghanaians to 7.05 (95% CI, 2.73-19.6) in the South African multiple ancestry group with the Gharahkhani PRS. The OR was 5.89 (95% CI, 1.72-24.30) for the highest quintile of the South African Black group compared with the lowest quintile and 7.05 (95% CI, 2.73-19.60) in the South African multiple ancestry group (Figure 1 and eTable 1 in Supplement 1). The performance of the GRS compared with a baseline model of age, sex, and the first 5 PCs was assessed by the AUROC. We observed a gain in the AUROC for the Tanzanian, South African multiple ancestry, African American (GGLAD and MVP), and European American groups (Figure 2 and eTable 2 in Supplement 1). However, the increase in AUROC was relatively modest in the Tanzanian (0.03 AUROC improvement from 0.66 baseline, P = .03) and African American (GGLAD: 0.02 AUROC improvement from 0.81 baseline, P < .001; MVP: 0.01 AUROC improvement from 0.69 baseline, P < .001) groups compared with the European American (0.06 AUROC improvement from 0.52 baseline, P < .001) group (eTable 2 in Supplement 1). We also evaluated the estimated proportion of POAG variance explained by the score. When comparing the genetic prediction performance of the Gharahkhani PRS from the African ancestral groups with the European American group, we observed lower phenotypic variance explained across all the African groups. Adding PRS to the baseline model, an improvement of the liability-R2 value was only detected in the South African multiple ancestry group (0.03 R2 increment over 0.01 baseline) and European American group (0.06 R2 increment over 0.002 baseline) (eTable 3 in Supplement 1). We attempted to consider differences in LD using the LD proxy score, however, this approach yielded unremarkable results across all groups when compared with the original Gharahkhani PRS (eTable 4 in Supplement 1).

Han PRS

The Han PRS, consisting of 223 SNVs, showed increases in ORs for the highest genetic risk quintile compared with the lowest risk quintile in the Tanzanian, Ghanaian, GGLAD and MVP African American, and European American groups (Figure 1 and eTable 1 in Supplement 1). In the European American group, the Han PRS demonstrated the most substantial OR estimate for the highest quintile compared with the lowest among all tested scores (7.24; 95% CI, 6.47-8.12, P < .001) (eTable 1 in Supplement 1). In contrast, when comparing the highest with the lowest quintiles, the OR estimates were lower in the Han PRS than in the Gharahkhani PRS in the Tanzanian, South African, Ghanaian, and GGLAD African American groups. Consequently, the Han PRS only exhibited superior high-risk identification in the MVP African American and European American groups. The prediction performance of the Han PRS demonstrated an improvement in the AUROC compared with the baseline model in the Tanzanian (0.03 AUROC improvement from 0.66 baseline, P = .02), African American (GGLAD: 0.01 AUROC improvement from 0.82 baseline, P = .005; MVP: 0.02 AUROC improvement from 0.71 baseline, P < .001), and European American (0.16 AUROC improvement from 0.52 baseline, P < .001) groups (the H blue bars) (Figure 2 and eTable 2 in Supplement 1). Regarding R2 by the Han PRS, increases for African ancestry groups were modest relative to the European American group. We only observed an improvement exceeding the contribution of the baseline alone in the European American group (0.08 R2 increment over 0.002 baseline) (eTable 3 in Supplement 1). The Han PRS outperformed all other scores regarding AUROC and R2 increases within the MVP African American and European American groups.

Craig PRS

Of the 3 scores, only the Craig PRS produced OR increases for the highest quintile in all tested groups ranging from 1.51 (95% CI, 1.05-2.18) in Ghanaians to 6.31 (95% CI, 5.67-7.04) in Europeans (Figure 1 and eTable 1 in Supplement 1). Prediction of POAG risk using the Craig PRS score increased the AUROC in the same groups as the Gharahkhani PRS (the G blue bars): Tanzanian (0.04 AUROC improvement from 0.66 baseline, P = .007), South African multiple ancestry (0.08 AUROC improvement from 0.59 baseline, P = .03), African American (GGLAD: 0.01 AUROC improvement from 0.81 baseline, P = .002; MVP: 0.01 AUROC improvement from 0.69 baseline, P < .001), and European American (0.16 AUROC improvement from 0.52 baseline, P < .001) (Figure 2 and eTable 2 in Supplement 1). Increases in R2 were smaller for all African groups than for European Americans. The Craig PRS showed a slight improvement in R2 for the South African multiple ancestry group compared with the baseline (0.03 R2 increment over 0.01 baseline) (eTable 3 in Supplement 1). Conversely, the increase in R2 within the European American group was more considerable (0.07 R2 increment over 0.002 baseline) (eTable 3 in Supplement 1), mirroring the performance observed with the Han PRS.

Discussion

This study evaluates 3 PRSs for POAG, derived from a meta-analysis of European and Asian population GWAS data, for distinguishing between cases and controls in a European ancestry group and 7 African ancestry groups. All 3 PRSs performed best for classifying POAG cases in the European American group, emphasizing the importance of constructing genetic risk scores using reference data from the same ancestral population as the study group. The improvement in AUROC remained modest for most African ancestral groups whereas performance was best in those groups with the highest proportion of European ancestry, the African American and South African multiple ancestry groups (Figure 2). Performance of risk scores is limited to stratifying individuals into case and control groups when comparing the lowest to the highest quintiles of genetic risk as defined by each risk score. This distinction does little to help guide clinical management.45,46

Strengths and Limitations

Our study has several strengths. We leverage ancestrally diverse data from 2 of the largest currently available datasets containing the genetic information of native African populations for glaucoma. However, even within African groups with low P values and relatively small CIs suggesting adequate power to detect differences, the OR gain was substantially higher in European groups. This suggests that the marked increase in ORs across quintiles of PRS in Europeans may not be solely attributable to higher statistical power but may also be influenced by ancestry-related factors. Others have reported this disparity in other diseases, and it has been suggested that this performance could be improved using models with more genetic variants.15,21,47,48 Our data do not support this—the Gharahkhani PRS performed as well as or better than the 2 larger models. The most important contributing factor to poor overall performance is the lack of population-specific genetic risk data for glaucoma. It is well recognized that individuals of African ancestry are underrepresented in GWAS studies, resulting in a small number of associated genetic variants with potentially imprecise estimates of effect sizes.49,50 At the same time, African continental and diaspora populations worldwide have very high levels of POAG.51 Extensive GWAS studies that include diverse African ancestry populations hold great promise for advancing our understanding of POAG risk in African individuals to enhance clinical management of this understudied and underserved patient population.52

We also recognize several limitations in this study. Despite using 2 of the most extensive available datasets, our African datasets had low statistical power, especially the South African group. This potentially limits the generalizability of our findings and emphasizes the need to support the implementation of more diverse genetic studies that include African populations. Furthermore, the GIGA and GGLAD studies draw cases and controls from hospital settings, whereas the MVP draws cases and controls from a defined cohort of VA medical center users. This difference in sampling methodology may impact the genetic risk profiles and the demographic composition, potentially accounting for the disparities observed in the baseline AUROC statistics. Moreover, the POAG definition in the MVP populations differed from that in the GIGA and GGLAD studies.

Conclusions

In this cross-sectional study, results suggest that adding genetic variants to the risk model moderately improved PRS performance for Africans, whereas more substantial improvements were seen in risk identification for Europeans. This emphasizes that simply including more variants in the PRS does not address the model performance disparity across ancestral populations and may reinforce it. Genetically diverse discovery datasets are necessary for building population-specific PRSs.

Supplement 1.

eFigure 1. Density Distributions

eTable 1. Highest Quintile Odds Ratios

eFigure 2. Case Proportions by Quintile

eTable 2. Area Under the Receiver Operating Characteristic Curve

eTable 3. R2 Values

eTable 4. Linkage Disequilibrium Proxy Polygenic Risk Score Results

Supplement 2.

Nonauthor Collaborators. The Genetics in Glaucoma Patients of African Descent (GIGA) Study Group, Genetics of Glaucoma in People of African Descent (GGLAD) Study Group, Million Veteran Program (MVP), and Cooperative Studies Program (CSP).

Supplement 3.

Data Sharing Statement.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Supplement 1.

eFigure 1. Density Distributions

eTable 1. Highest Quintile Odds Ratios

eFigure 2. Case Proportions by Quintile

eTable 2. Area Under the Receiver Operating Characteristic Curve

eTable 3. R2 Values

eTable 4. Linkage Disequilibrium Proxy Polygenic Risk Score Results

Supplement 2.

Nonauthor Collaborators. The Genetics in Glaucoma Patients of African Descent (GIGA) Study Group, Genetics of Glaucoma in People of African Descent (GGLAD) Study Group, Million Veteran Program (MVP), and Cooperative Studies Program (CSP).

Supplement 3.

Data Sharing Statement.


Articles from JAMA Ophthalmology are provided here courtesy of American Medical Association

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