Development and implementation of polygenic risk score in Vietnamese population

Research and Development on Information and Communication Technology  
Development and Implementation of  
Polygenic Risk Score in Vietnamese Population  
Nguyen Tran The Hung, Le Duc Hau  
Department of Computational Biomedicine, Vingroup Big Data Institute, Hanoi, Vietnam  
Correspondence: Le Duc Hau, [email protected]  
Communication: received 18 October 2019, revised 23 December 2019, accepted 29 December 2019  
Digital Object Identifier: 10.32913/mic-ict-research.v2019.n2.893  
The Editor coordinating the review of this article and deciding to accept it was Prof. Le Hoang Son  
Abstract: Recent technological advancements and availabil-  
ity of genetic databases have facilitated the integration of  
genetic factors into risk prediction models. A Polygenic Risk  
Score (PRS) combines the effect of many Single Nucleotide  
Polymorphisms (SNP) into a single score. This score has  
lately been shown to have a clinically predictive value in  
various common diseases. Some clinical interpretations of  
PRS are summarized in this review for coronary artery  
disease, breast cancer, prostate cancer, diabetes mellitus, and  
Alzheimer’s disease. While these findings gave support to the  
implementation of PRS in clinical settings, the populations  
of interest were derived mainly from European ancestry.  
Therefore, applying these findings to non-European ancestry  
(Vietnamese in this context) requires many efforts and cau-  
tions. This review aims to articulate the evidence supporting  
the clinical use of PRS, the concepts behind the validity of  
PRS, approach to implement PRS in Vietnamese population,  
and cautions in selecting methods and thresholds to develop  
an appropriate PRS.  
Alzheimer disease [2]. Therefore, there is a growing interest  
in combining all the small SNP effects into a single score  
that has significant and applicable values [3, 4].  
2. PRS Calculation  
In its simplest form, the PRS of an individual can be  
calculated as the sum of all effect sizes of the effective  
alleles observed in its genotype. The formula to calculate  
the PRS is given as follows:  
<
Õ
b
PRS8 =  
G8 9 × ꢀ9,  
9=1  
where PRS8 is the risk score for the 8th individual, < is  
the number of SNPs included in the calculation, G8 9 is the  
genotype of the 8th individual for the 9th SNP (can be 0, 1,  
b
or 2 depending on the inheritance model), and ꢀ9 is the  
effect size of the 9th SNP, usually obtained from GWAS  
Keywords: Genetic, clinical, single nucleotide polymoyphism  
(SNP), polygenic risk score (PRS).  
summary statistics [4].  
Although the concept of PRS is as old as the finding  
of genetic materials (DNA), modern technology allows the  
integration of more genetic variants and more precise effect  
sizes. Therefore, there are numerous considerations and  
thresholds related to developing and validating the formula  
of PRS that are still controversial [5].  
I. RENEWED INTEREST IN POLYGENIC RISK SCORE  
1. Definition  
A Polygenic Risk Score (PRS) in the context of genetic  
studies is a mathematical aggregation of risk effects con-  
ferred by many Single Nucleotide Polymorphisms (SNP).  
Each SNP contributes a small effect to the development of  
a disease or a complex trait of interest. In the early days  
of Genome-Wide Association Study (GWAS), researchers  
expected to find genetic variants that have a large effect  
on disease risk [1]. While the sample size of GWASs has  
already surpassed hundreds of thousand of individuals, they  
failed to capture the genetic variants that can explain the  
heritability of common diseases, such as breast cancer,  
prostate cancer, coronary artery disease, diabetes mellitus,  
3. Advancements in the Field of Genetics  
At this junction, there are many developments of tech-  
nology and findings of new studies that facilitate the  
development of PRS. The availability of various popula-  
tions’ reference human genomes can be accessed publicly  
in the 1000 genomes project [6]. Thousands of GWASs  
comprise of up to millions of samples. These GWAS  
summary statistics data can be easily accessed through the  
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Research and Development on Information and Communication Technology  
“GWAS Catalog” [7], which is an online database with  
more than 4000 published studies.  
New analysis methods for developing the PRS without  
relying solely on genome-wide significant hits continue to  
appear, such as Clumping + Thresholding [8], Penalized  
Regression [9]. The access to large genotype and phe-  
notype data of large longitudinal cohorts becomes eas-  
ier through online databases such as “dbGAP” [10] and  
“UK biobank” [11].  
II. CLINICAL USAGE OF PRS  
While making clinical decisions, doctors often have to  
classify the susceptibility of a patient based on known risk  
Figure 1. CAD incident by PRS group in statin primary prevention trial.  
factors. This disease risk classification is very important in  
providing an appropriate recommendation for the patient.  
A group of individuals having certain risk factors could  
have higher relative risk than the general population to  
guarantee different clinical management. If existing medical  
intervention can provide more benefits than adverse effects,  
with reasonable costs, this group of high-risk individuals  
would receive more benefits from it. Recent studies have  
suggested that genetic profiling using the PRS can provide  
some clinical utilities [12].  
Adapted from a study by Natarajan et al. (2017) [17]. **: chi-square test  
with p-value < 0.01. ***: chi-square test with p-value < 0.001.  
having high genetic risk for CAD, who can receive more  
benefits from primary prevention with statin therapy [17].  
Patients having the top quintile of PRS have higher risk of  
subclinical atherosclerosis and receive greater absolute risk  
reduction of CAD event from statin therapy (Figure 1).  
PRS analysis and its interpretation revolved around some  
situations: risk prediction performance of PRS indepen-  
dently or in combination with other non-genetic risk factors  
and estimation of lifetime risk trajectories. Some recent  
studies have proposed some clinical interpretations of PRS  
that can modify therapeutic intervention, disease screening  
and life planning [13]. This review highlights some recent  
findings of PRS in certain common diseases: coronary  
artery disease, diabetes mellitus, breast cancer, prostate  
cancer and Alzheimer’s disease.  
2. Breast Cancer  
Breast cancer screening has been recommended for  
women older than 50 without major risk factors for a long  
time [18]. The reasoning behind screening for breast cancer  
in women older than 50 is reducing disease mortality and  
decreasing false positive diagnosis. A study by Pashayan et  
al. argued that a well-defined risk-stratified screening strat-  
egy would improve the quality of life of women and save  
resources [19]. Based on this risk/benefit threshold, a risk  
prediction model combining clinical risk factors and the  
PRS could identify a subgroup of women who had relative  
risk of developing breast cancer higher than that of 50-year-  
old women [20]. These high-risk individuals could benefit  
from earlier screening tests and assertive lifestyle change to  
reduce certain risk factors. The women in the top quintile  
of PRS could have the same relative risk as average 50-  
year-old women around 5-10 years earlier (Figure 2).  
1. Coronary Artery Disease  
Clinical risk scores like the Framingham risk score is  
a traditional tool in evaluating 10-year coronary artery  
disease (CAD) risk [14]. This score uses clinical risk factors  
to score each individual and infer his chance of developing  
CAD in the next 10 years. Abraham et al. have proved that  
integrating the PRS in traditional clinical risk model can  
better capture the lifetime risk of CAD in patients [15].  
This argument was supported by better C-statistic (measure  
of goodness-of-fit) in the combined model as compared to  
the clinical one. More importantly, men in the top quintile  
of PRS had 10% cumulative CAD risk around 15 years  
earlier than men in the bottom quintile.  
3. Prostate Cancer  
Current medical guideline suggests that the age to con-  
sider prostate cancer screening is 50 years for average-risk  
men as long as life expectancy is at least 10 years [22].  
A study by Seibert et al. [23] argued that the PRS was a  
significant predictor for the age of prostate cancer onset. It  
was also a relatively inexpensive evaluation of individual’s  
benefits from prostate cancer screening.  
In the primary prevention setting, statin can be used to  
treat atherosclerosis and reduce the risk of cardiovascular  
events [16]. The PRS can identify a group of patients  
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additive model tests could avoid multiple comparisons but  
overlooked the other inheritance models. Besides, when  
the gene-gene interaction and gene-environment exposure  
were taken into account, the model became much more  
complicated and current statistical methods could not keep  
up with this complexity [30, 31].  
2. Content  
In the context of implementation, the PRS was used to  
predict the genetic disease risk of common diseases. The  
content of the PRS needed to capture all of the genetic  
variations with the purpose of reflecting the genetic liabil-  
ity of the disease. However, for many common diseases,  
genetic variation only accounted for a small portion of the  
disease phenotype [2].  
Figure 2. Cumulative breast cancer risk stratified by PRS quintile. Adapted  
from a study by Maas et al. (2016) [21].  
4. Diabetes Mellitus  
Early detection of individuals with high risk of type 1  
diabetes (T1D) allows better monitoring and prevention of  
disease progression. Redondo et al. evaluated the perfor-  
mance of PRS on T1D patients’ relatives without diabetes  
and with one or more positive autoantibodies [24]. Pro-  
gression to T1D was best predicted by a combined model  
of PRS, number of positive auto-antibodies, DPT-1 Risk  
Score [25], and age. Individuals at high risk of developing  
T1D can benefit from monitoring and prevention trials.  
The diagram in Figure 3 illustrates the contributing  
factors to T2D development and the way some T2D-risk  
prediction model were constructed. Conceptually, the SNPs  
having effect on a complex trait such as T2D consist  
of SNPs that modified intermediate phenotypes (blood  
pressure, BMI), which eventually contribute to the risk of  
T2D. These intermediate phenotypes present themselves  
as clinical risk factors. T2D is also affected by factors  
independent with genetics such as age, lifestyle (Figure 3).  
A prospective cohort study by Lall et al. [26] used  
a PRS that had the strongest association with type 2  
diabetes (T2D) in a population-based cohort and evaluated  
its performance on a prospective individual risk assessment.  
The hazard for incident T2D was more than 3 times higher  
in the top quintile of PRS, as compared to others.  
The conventional risk prediction model used for T2D in  
clinical settings only included clinical risk factors [32]. Re-  
cent findings in the field of genetics suggested that combin-  
ing clinical risk factors and the PRS could improve the cur-  
rent risk prediction model and the cost-benefit metrics [33].  
The caveat of this approach was that many clinical risk  
factors are not independent with genetics. The combined  
prediction model might have the effect of genetic factors  
and clinical factors of the same pathogenic mechanism  
counted simultaneously (e.g., the effect of SNPs associated  
with blood pressure and the effect of clinical high blood  
pressure were both included in the prediction model in  
Figure 3). Although the combined model showed improved  
C-statistic, a single mechanism (blood pressure/BMI) was  
counted twice: one in the genetic feature and the other  
in the clinical one. The outcome would be biased toward  
that mechanism. Another approach was to evaluate the  
prediction model only with the PRS, stratified by age [26].  
This approach highlighted the independent nature of the  
PRS and visualized the cumulative risk of the disease of  
the high-risk group compared to the general population.  
5. Alzheimer’s Disease  
One of the most common causes of dementia is  
Alzheimer’s disease. Desikan et al. studied the PRS per-  
formance in stratifying Alzheimer’s disease risk [27]. This  
study argued that the PRS could be integrated into screen-  
ing for individuals with age-specific high genetic risk for  
Alzheimer’s disease. This finding has not been found its  
use in clinical settings yet, but may prove to be useful for  
therapeutic trials.  
III. VALIDITY OF PRS  
1. Construct  
When the PRS was constructed, it was assumed that  
SNPs had additive effects on the disease. Because of the  
large number of SNPs and its unexplained characteristics  
with the disease of interest, GWAS typically chose the  
additive model for statistical analysis [28]. However, the  
biological reality is assuredly more complicated than that.  
The mode of inheritance of a SNP could be additive,  
multiplicative, recessive or dominant [29]. Performing only  
3. Criterion  
Whether the PRS has valid predictive power depends on  
the specific disease and population. A review by Duncan et  
al. [34] found out that the majority of PRS studies included  
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Research and Development on Information and Communication Technology  
Figure 3. Risk factors of T2D and content of the prediction model for T2D.  
European ancestry and East Asian ancestry participants. A  
PRS derived from the European population had lower per-  
formance in the non-European population. As a result, if we  
wanted to apply PRS utilities in the Vietnamese population,  
we had to improve methodological choice and threshold to  
accommodate the difference in linkage disequilibrium and  
variant frequency between Vietnamese and European/East-  
Asian. The clinical utility of the PRS needed to be validated  
in a prospective cohort study [35].  
the genotype of an individual for known variants, as well  
as identify variants that may be unique to that person [38].  
The cost of genotyping array is lower and, thus, more  
suitable for large scale research in the population. However,  
the commercial genotyping array used in GWAS has a  
strong ascertainment bias because SNPs are chosen from  
European individuals [39]. The best way to overcome  
this problem is to design an SNP-array suitable for the  
Vietnamese population.  
2. Available Databases  
IV. IMPLEMENTING PRS IN VIETNAMESE  
POPULATION  
The 1000 genome project, which shared reference  
genome from diverse populations, contained over 88 million  
variants from 2504 individuals [6]. It provided a broad  
representation of human genomes in different populations  
and ethnicities. This database contained 101 Vietnamese  
individuals (Kinh ethnic from Ho Chi Minh city). The  
availability of the Vietnamese reference genome is very  
important for researchers who are interested in conducting  
genetic research in Vietnam. The more references there are,  
the better it can represent Vietnamese human genomes.  
As a result, risk prediction based on genetic factors will  
be more reliable and accurate. To this end, a Vietnamese  
genetic database is being built [40]. As data grow larger, the  
prospect of implementing genetic findings in Vietnamese  
clinical settings become more imminent.  
1. Method to Read DNA  
Genotyping is a method of determining which genetic  
variants an individual possesses. SNP microarrays allow  
detection of hundreds of thousands of pre-determined  
SNPs. In genetic research, SNP arrays are most frequently  
used for GWASs. A commercial genotyping array included  
around 500, 000 SNPs and cost around 100 USD [37].  
Sequencing is the process of determining the DNA  
sequence, which is the exact order of DNA’s bases: adenine  
(A), guanine (G), cytosine (C), and thymine (T). Whole-  
genome sequencing and whole-exome sequencing are more  
expensive but they allow a more precise detection of  
genetic variations (e.g., structural variants). Depending on  
the region, a given stretch of sequence may include some  
DNA that varies between individuals, in addition to the  
constant region. Thus, sequencing can be used to determine  
Of course, this is only the first step in genetic research  
in Vietnam. In order to catch up with international re-  
search and development, Vietnam still has a long way  
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Figure 4. Resources of genetic studies and PRS analysis. Adapted from a tutorial by Choi et al. (2018) [36].  
to go. There are some established databases of human  
genotype-phenotype like dbGaP [41] and PheGenI [42].  
These databases allow researchers to share their datasets  
and to perform large scale and complex analysis on various  
diseases. A genotype-phenotype database of the Vietnamese  
population for replicating published genetic findings is  
sorely needed. The availability of such a database will  
facilitate the replication of PRS research with high applica-  
bility and will optimize the predictive performance in the  
Vietnamese population. Besides, replication of GWAS with  
a large Vietnamese sample size will also provide valuable  
information for genetic research.  
2) Exclude individuals with genotyping rate greater  
than 2%;  
3) Exclude individuals with sex discrepancies be-  
tween recorded data and their X chromosome’s  
heterozygosity;  
4) Include SNPs with minor allele frequency (MAF)  
above the threshold (based on the sample size of the  
study, larger sample size can use lower threshold);  
5) Exclude SNPs that deviate from Hardy-Weinberg  
equilibr−iu10m (for binary traits HWE p-value is less  
than 10 , for quantitative traits HWE p-value is less  
than 10−6);  
6) Exclude individuals with heterozygosity rate deviated  
more than 3 standard deviations from the population  
mean;  
V. POLYGENIC RISK SCORE ANALYSIS  
7) Perform principal component analysis on the training  
data and using the first 10 eigenvectors as covariates.  
Polygenic risk score calculation can be characterized by  
two input data sets: the base data (the summary statistics  
of the latest GWAS concerning the disease of interest) and  
the training data (the individual genotype-phenotype from  
the population of interest) as illustrated in Figure 4.  
All these steps can be done with plink 1.90 software [43].  
Because base data and training data come from different  
sources, some QC steps need to be taken according to  
Choi et al. [36]:  
1) Check the integrity of the transferred file with a  
software like md5sum [44];  
1. Quality Control of Input Data  
Since the base data come from GWAS, input data must  
be quality-controlled (QC) according to the standard of  
GWAS. According to a tutorial on conducting GWAS by  
Marees et al. [28], QC steps for a successful GWAS are:  
2) Ensure that input data have genomic position of the  
same genome build with LiftOver program [45];  
3) Define the effect allele and the reference allele from  
the base data since some GWAS summaries cate-  
gorize the allele as risk allele/non-risk allele and  
major/minor allele;  
1) Exclude SNPs that are missing in greater than 2% of  
the subjects;  
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Research and Development on Information and Communication Technology  
TABLE I  
DIFFERENT METHODS OF COMPUTING PRS. ADAPTED FROM A STUDY BY CHOI ET AL. (2018) [36]  
Clumping + thresholding  
Penalized Regression  
Bayesian Shrinkage  
Shrinkage of SNPs’  
Effect Size  
P-value threshold  
LASSO, penalty parameters, Elastic Net  
Fraction of causal SNPs  
Handling of Linkage  
Disequilibrium  
Clumping  
LD matrix integral to the algorithm  
Lassosum [48] bigstatr [9]  
Shrink effect sizes with respect to LD  
LDpred [49]  
Software  
PRSice [8]  
4) Process the ambiguous SNPs due to unknown chro-  
mosome strand (sense/antisense) from different DNA  
read platform; removing duplicated SNPs;  
5) Ensure the independence of base data and training  
data by removing overlapping samples and closely  
related individuals (1st/2nd degree relatives);  
statistics. This technique allows for decreasing the variance  
at the cost of introducing some bias. The selection of tuning  
parameters _ and B in the elastic net technique results in a  
model’s best fit. This model is complicated to calculate but  
performs better than the clumping-and-thresholding method  
in a small sample size [9].  
6) Check chip-heritability from GWAS summary statis-  
tics by using LD score regression [46] to avoid reach-  
ing misleading conclusion (because the predictive  
power of the PRS cannot surpass the power and  
predictive accuracy of the base GWAS [47]).  
Bayesian shrinkage is a method that infers the mean  
effect size of SNP based on a reference LD panel and  
assumption of causal SNP fraction in the genotype. Simula-  
tion and empirical data prove that this method outperforms  
the clumping-and-thresholding method, particularly in a  
large sample size [49, 50].  
2. PRS Calculation  
Penalized regression and Bayesian shrinkage lead to  
millions of SNPs included in the PRS calculation. Most  
of these SNPs have a negligible effect on individual risk  
score. Their effect sizes are so small and would have been  
zero if the effect size would be rounded up to 3 or 4 digits  
after the decimal point. This approach aims to maximize the  
C-statistics even if the majority of the included SNPs have  
minimal effect on individual risk score [50]. This approach,  
however, convolutes the PRS formula beyond the biological  
and medical interpretation.  
After QC has been performed, PRSs are calculated for all  
individuals in the training data. There are many methods to  
calculate the polygenic risk score (see Table I), but a good  
method has to take into account the following factors. The  
first factor is the effect sizes of SNPs taken from GWAS  
summary statistics. These effect sizes consist of true associ-  
ation with the disease and some degree of unknown random  
variations which produce “winner’s curse” effect among the  
most significant SNPs. The second one is the number of  
SNPs included in the calculation. And the third one is the  
correlation among SNPs, i.e., linkage disequilibrium. LD  
difference between base and training data can make the  
PRS misestimate the risk of disease.  
3. Optimizing PRS and Result Presentation  
The association between the PRS and the phenotype  
can be quantified with goodness-of-fit metrics such as the  
estimate of effect size (beta for quantitative phenotype and  
OR for binary phenotype), ?-value of the null hypothesis  
test of no association, explained variance ('2) and area  
under the curve (AUC).  
Clumping-and-thresholding is the most common method  
to compute the PRS. Clumping in this context means  
selecting the most significant SNP in a block of related  
SNPs based on LD (usually A2 > 0.2). The ?-value  
threshold is usually genome-wide significant 5 × 10−8 or  
the threshold that maximizes the AUC is selected. The  
clumping-and-thresholding method is fast and easy to use. It  
can capture the independent effect of the SNPs. However, a  
compelling criticism of this method is the removal of SNPs  
in LD with arbitrary A2 value. Clumping-and-thresholding  
is automated in PRSice software [8]. This is one of the  
most common tools for computing the PRS. The processes  
of calculating, evaluating and visualizing the result are  
automated in the software.  
Explained variance is a statistical measure to quantify the  
discrepancy between the PRS model and the observed phe-  
notype. A higher percentage of explained variance means  
a better association of the model, which also means that  
the PRS has better predictive performance. In linear regres-  
sion analysis for quantitative phenotype, explained variance  
is the coefficient of determination. In logistic regression  
analysis for binary phenotype, explained variance is the  
pseudo-'2. Various types of pseudo-'2 metrics are used in  
epidemiology field. Among them, Nagelkerke '2 is perhaps  
the most popular [51].  
Penalized regression is a method to integrate LD infor-  
mation of the population of interest into GWAS summary  
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The receiver operating characteristic curve illustrates the  
true positive rate (sensitivity) versus false-positive rate  
(specificity). The AUC represents the accuracy of the test.  
A test with AUC between 0.9–1 is an excellent test. A test  
with AUC between 0.5–0.6 is a worthless test [52].  
invasive procedure (e.g., blood draw or saliva sample)  
and a single genotype data can be analyzed to provide  
estimations for many diseases simultaneously. Although the  
medical community still has doubt and hesitation regarding  
implementation of the PRS, it will continue to improve and  
have larger impact in the near future.  
Result presentation of the PRS analysis should emphasize  
its relevant usage which is a prognosis of disease liability.  
The main goal of the PRS is the identification of a group  
of individuals with high-risk of disease based on genetic  
factors. Therefore, the result should stratify the population  
into distinct tiers of risk based on the percentile rank cut-  
off value, usually top 1 percentile, top 10 percentile, top 20  
percentile, etc., e.g., as presented in Figure 1. Generally,  
the medical community has already defined the appropriate  
level of risk versus benefits that justifies certain medical  
interventions [53, 54]. When an individual is determined to  
have high-risk for a disease, we can infer the relative risk  
of said individual compared to the reference. The higher  
the relative risk of said individual is, the more justified the  
medical intervention becomes.  
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4. Validating PRS Performance  
A common concern in PRS analysis is whether the most  
optimized PRS overfits the training data [56]. As a result,  
applying said PRS to the general population can lead to  
inflated results and false conclusions. The best strategy  
to prevent overfitting of the PRS-based prediction model  
is to validate its accuracy on an independent data set.  
In the absence of an independent data set, the training  
data can be divided into 2 separated data sets, one for  
optimizing the PRS and the other for performing out-of-  
sample prediction [57].  
VI. CONCLUSION  
The cost of reading DNA is becoming more and more  
affordable through advancement of genotyping and se-  
quencing technologies. Alongside the development of data  
storage, new computing methods and abundance of dis-  
ease databases, the PRS has provided better accuracy to  
existing models of risk prediction for common diseases.  
Consequently, individual clinical management (e.g., disease  
screening and therapeutic intervention) can be personalized  
based on individual genetic information. This genetic infor-  
mation can be obtained at any point in life with a minimally  
81  
                                 
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Le Duc Hau obtained his PhD degree  
in Bioinformatics from University of Ul-  
san, Republic of Korea in 2012. He is  
now leading the Department of Compu-  
tational Biomedicine, Vingroup Big Data  
Institute, Vietnam. He has been focus-  
ing on proposing computational methods  
for disease- and drug-related problems in  
personalized medicine, especially on identification of disease-  
associated biomarkers, prediction of drug targets and response.  
In parallel, he has been developed bioinformatics tools. So far,  
he has been published more than fifty papers in well-recognized  
journals and conferences, nearly a half of those are in ISI-indexed  
journals. In addition, he has been a member of program com-  
mittees and reviewer of several international conferences/journals.  
Moreover, he is a principal investigator and a key member of some  
national/ministry-level projects. Specially, he is the principal in-  
vestigator of the biggest genome project in Vietnam (i.e., building  
databases of genomic variants for Vietnamese population). Finally,  
he has been collaborating with some well-recognized international  
research institutes.  
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outcome with microarrays: A multiple random validation  
strategy,” The Lancet, vol. 365, no. 9458, pp. 488–492, 2005.  
Nguyen Tran The Hung received his doc-  
tor of medicine degree from Universities of  
Medicine and Pharmacy of Ho Chi Minh  
city (Viet Nam) in 2016. He then got a  
master degree in biomedical science from  
China Medical Universities (Taichung, Tai-  
wan) in 2019. His research field is human  
genetic and diabetes mellitus. He worked  
briefly as a pediatrician before pursuing his career in academia as  
a research scientist at Vingroup Big Data Institute from 2019 until  
now. His thesis on type 2 diabetic nephropathy and the application  
of polygenic risk score made him believe in the potential impact  
that genetic research can make in healthcare.  
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