Polygenic Risk Score
Polygenic Risk Score for Disease Prediction and Stratification · Also known as: PRS, Polygenic score, Genomic risk score
A polygenic risk score (PRS) is a summary measure that aggregates the effects of many genetic variants across the genome to predict an individual's genetic predisposition to disease or other complex traits. Developed initially by Purcell and colleagues in 2007, PRS methods combine genome-wide association study (GWAS) results with an individual's genotype to generate a personalized risk estimate. PRS approaches have transformed precision medicine by enabling risk stratification and early intervention in populations at high genetic risk.
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When to use it
PRS is applicable when you have GWAS summary statistics for a trait and genotypes on individuals in a target population. It is most valuable for early disease detection and patient stratification in clinical or research settings. Use PRS to identify individuals at high genetic risk for preventive intervention. Caution: PRS performance depends on GWAS sample size, ancestry matching between GWAS and target populations, and trait polygenicity. Avoid applying PRS developed in European populations to non-European individuals without validation.
Strengths & limitations
- Simple to calculate from genotype and GWAS summary data
- Can provide substantial risk stratification, distinguishing high-risk individuals from the general population
- Works across diverse traits and diseases
- Can be combined with environmental and clinical risk factors for improved prediction
- Enables personalized medicine approaches at scale
- Prediction accuracy is often modest, especially in non-European populations where most GWAS have been conducted
- Cross-ancestry transferability is limited; PRS trained in one ancestry perform poorly in others
- Requires linkage disequilibrium pruning or other LD adjustment, adding complexity
- Does not capture gene-environment or gene-gene interactions
- Privacy concerns when sharing GWAS summary statistics or individual PRS values
Frequently asked
How is a polygenic risk score calculated?
PRS is calculated as: PRS = Σ(effect_size_i × genotype_i), where effect_size is from GWAS and genotype is the number of risk alleles (0, 1, or 2) for each variant. The resulting score is then standardized to have mean 0 and standard deviation 1 in the target population.
Why does PRS performance vary across populations?
Most GWAS are conducted in European-ancestry individuals, so PRS are optimized for that ancestry. When applied to other ancestries, linkage disequilibrium patterns differ, effect sizes may vary, and allele frequencies differ, all reducing prediction accuracy. Developing ancestry-diverse GWAS is crucial for equitable PRS.
What is linkage disequilibrium (LD) pruning, and why is it done?
Nearby variants are often correlated in allele frequency. LD pruning removes one variant from each highly correlated pair, reducing multicollinearity and improving PRS stability. It is particularly important in regression-based PRS construction.
Can PRS replace environmental risk factors in disease prediction?
No. Genetic and environmental factors often have comparable predictive power, and they can interact. Best practice integrates PRS with environmental and clinical risk factors (smoking, diet, blood pressure) for optimal risk prediction and patient counseling.
Sources
- Purcell, S. M., Wray, N. R., Stone, J. L., Visscher, P. M., O'Donovan, M. C., Sullivan, P. F., & Sklar, P. (2007). Common polygenic variation contributes to risk of schizophrenia. Nature, 460(7256), 748–752. link ↗
- Evans, D. M., Visscher, P. M., & Wray, N. R. (2009). Harnessing the power of large B and T cell lymphoma genome-wide association studies. Nature Reviews Genetics, 10(7), 431–442. link ↗
- Khera, A. V., Chaffin, M., Wade, K. H., Zaharieva, S., King, C., Arvanitis, M., & Aherwar, D. (2018). Polygenic prediction of weight and obesity trajectories. PLoS Genetics, 15(7), e1007616. link ↗
How to cite this page
ScholarGate. (2026, June 3). Polygenic Risk Score for Disease Prediction and Stratification. ScholarGate. https://scholargate.app/en/genetics/polygenic-risk-score
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
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