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Polygenic risk prediction: why and when out-of-sample prediction R 2 can exceed SNP-based heritability
In polygenic score (PGS) analysis, the coefficient of determination (R ) is a key statistic to evaluate efficacy. R is the proportion of phenotypic variance explained by the PGS, calculated in a cohort that is independent of the genome-wide association study (GWAS) that provided estimates of allelic...
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Published in: | American journal of human genetics 2023-07, Vol.110 (7), p.1207 |
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Main Authors: | , , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Online Access: | Get full text |
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Summary: | In polygenic score (PGS) analysis, the coefficient of determination (R
) is a key statistic to evaluate efficacy. R
is the proportion of phenotypic variance explained by the PGS, calculated in a cohort that is independent of the genome-wide association study (GWAS) that provided estimates of allelic effect sizes. The SNP-based heritability (h
, the proportion of total phenotypic variances attributable to all common SNPs) is the theoretical upper limit of the out-of-sample prediction R
. However, in real data analyses R
has been reported to exceed h
, which occurs in parallel with the observation that h
estimates tend to decline as the number of cohorts being meta-analyzed increases. Here, we quantify why and when these observations are expected. Using theory and simulation, we show that if heterogeneities in cohort-specific h
exist, or if genetic correlations between cohorts are less than one, h
estimates can decrease as the number of cohorts being meta-analyzed increases. We derive conditions when the out-of-sample prediction R
will be greater than h
and show the validity of our derivations with real data from a binary trait (major depression) and a continuous trait (educational attainment). Our research calls for a better approach to integrating information from multiple cohorts to address issues of between-cohort heterogeneity. |
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ISSN: | 1537-6605 |