Twin studies have long been recognized as a powerful method for investigating the influence of genetic and environmental factors on human traits, as they effectively control for genetic variation between individuals (Galton, Reference Galton1883; Guo, Reference Guo2001; Martin et al., Reference Martin, Boomsma and Machin1997). Twin studies were first introduced in the late 19th century to examine the contributions of nature and nurture to human traits (Galton, Reference Galton1883). The classical twin method was later systematically formalized in 1924 when Siemens introduced structured approaches to zygosity determination and comparison of concordance rates between monozygotic (MZ) and dizygotic (DZ) twins, which was complemented by Merriman’s early empirical research on intellectual resemblance among twins (Merriman, Reference Merriman1924; Siemens, Reference Siemens1924). Since then, twin studies have been foundational in behavioral genetics, psychology, epidemiology, and molecular biology (Boomsma et al., Reference Boomsma, Busjahn and Peltonen2002; Guo, Reference Guo2001). By comparing MZ (identical) and DZ (fraternal) twins, these studies enable the estimation of heritability (Boomsma et al., Reference Boomsma, Busjahn and Peltonen2002), which is defined as the proportion of trait variation in a population that is attributable to genetic differences among individuals (Falconer, Reference Falconer1981; Visscher et al., Reference Visscher, Hill and Wray2008). Behavioral geneticists have historically used twin studies to analyze the effects of shared environments (e.g., family) and unique environmental factors (e.g., individual experiences) separately from genetic influences (Goldsmith & Lemery-Chalfant, Reference Goldsmith, Lemery-Chalfant and Elliot2013; Guo, Reference Guo2001).
A twin registry is a unique, country-level systematic database, typically managed by academic or clinical institutions. These databases collect comprehensive information on both MZ and DZ twins, including genetic, medical, psychological, and environmental data, and often include information on other family members as well (Hur et al., Reference Hur, Bogl, Ordoñana, Taylor, Hart, Tuvblad, Ystrom, Dalgård, Skytthe and Willemsen2019; Sahu & Prasuna, Reference Sahu and Prasuna2016; Willemsen et al., Reference Willemsen, de Geus, Bartels, van Beijsterveldt, Brooks, Estourgie-van Burk, Fugman, Hoekstra, Hottenga and Kluft2010). Globally, there are more than 60 twin registries worldwide, with the majority located in Western countries, collectively comprising over one million twin individuals (Boomsma et al., Reference Boomsma, Busjahn and Peltonen2002; Hur et al., Reference Hur, Bogl, Ordoñana, Taylor, Hart, Tuvblad, Ystrom, Dalgård, Skytthe and Willemsen2019; Kaprio, Reference Kaprio2013; Skytthe et al., Reference Skytthe, Christiansen, Kyvik, Bødker, Hvidberg, Petersen, Nielsen, Bingley, Hjelmborg and Tan2013). Figure 1 illustrates a map showing the global distribution of twin registries, with a particular focus on the Middle East and North Africa (MENA) region, highlighting the scarcity of established registries.
The distribution of twin registries around the world, highlighting the Middle East and North Africa region. (Hur et al., Reference Hur, Bogl, Ordoñana, Taylor, Hart, Tuvblad, Ystrom, Dalgård, Skytthe and Willemsen2019; Nanakorn et al., Reference Nanakorn, Chusilp and Kutanan2013).
Note: Consortium-level collaborations (e.g., CNTR, CODATwins, INTR) are not shown on the map.
The Danish Twin Registry, established in 1954, is recognized as the first national twin registry and remains one of the most comprehensive, currently including more than 175,000 twin individuals across multiple birth cohorts (Harvald et al., Reference Harvald, Hauge, Kyvik, Christensen, Skytthe and Holm2004; Hur et al., Reference Hur, Bogl, Ordoñana, Taylor, Hart, Tuvblad, Ystrom, Dalgård, Skytthe and Willemsen2019; Skytthe et al., Reference Skytthe, Kyvik, Holm and Christensen2011). Earlier twin registries existed prior to this period; however, they were limited to regional or institutional cohorts rather than national coverage. Since then, and over the past few decades, well-established twin registries have been created in countries such as Sweden (Magnusson et al., Reference Magnusson, Almqvist, Rahman, Ganna, Viktorin, Walum, Halldner, Lundström, Ullén and Långström2013), Denmark (Skytthe et al., Reference Skytthe, Kyvik, Holm and Christensen2011), Norway (Nilsen et al., Reference Nilsen, Knudsen, Gervin, Brandt, Røysamb, Tambs, Ørstavik, Lyle, Reichborn-Kjennerud and Magnus2013), Australia (Hopper et al., Reference Hopper, Foley, White and Pollaers2013), the Netherlands (Willemsen et al., Reference Willemsen, de Geus, Bartels, van Beijsterveldt, Brooks, Estourgie-van Burk, Fugman, Hoekstra, Hottenga and Kluft2010), and the United Kingdom (Spector & Williams, Reference Spector and Williams2006).
Despite the presence of numerous well-established twin registries worldwide, there is a notable absence of such registries in the Arab region. Populations in this region offer unique options to investigate human complex traits and conditions in populations with unique genetic backgrounds, often in large pedigrees with high rates of consanguinity and inbreeding, and also with distinct environmental exposures (Al-Gazali & Hamamy, Reference Al-Gazali and Hamamy2014; Fareed & Afzal, Reference Fareed and Afzal2017; Tadmouri et al., Reference Tadmouri, Nair, Obeid, Al Ali, Al Khaja and Hamamy2009). Individuals of Arab ancestry account for 5% of the global population (Bhattacharya et al., Reference Bhattacharya, Chen, Shim, Kuwahara, Gao, Alkuraya and Fahed2023) but currently make up fewer than 0.2 % of participants in published genomewide association studies (Bhattacharya et al., Reference Bhattacharya, Chen, Shim, Kuwahara, Gao, Alkuraya and Fahed2023), further underscoring the urgent need for population-specific resources.
We established the Qatar Twin Registry (QTR) as the first in Qatar and the Arab world, and the second in the Middle East and North Africa region, following the Isfahan Twins Registry (ITR) in Iran (Gharipour et al., Reference Gharipour, Javanmard, Mansourian, Sabri, Khosravi, Dianatkhah, Sadeghian, Jabarzare and Sarrafzadegan2019). This project is led by researchers at Qatar University (QU) in collaboration with the Qatar Precision Health Institute (QPHI). The QTR is designed to support twin-based research through comprehensive phenotyping, longitudinal follow-up, generation of whole genome sequencing and other multiomics data generation by linking to the Qatar Biobank (QBB) and Qatar Genome Project. QTR has been established, and the recruitment is ongoing for its pilot phase, which aims to recruit 100–250 twin pairs (and higher order multiples) in addition to their first-degree relatives, within an anticipated timeframe of 3 years. The pilot phase is designed to establish the registry infrastructure, determine zygosity using whole-genome sequencing, and enable classical twin design analyses to estimate heritability of complex traits such as obesity, type 2 diabetes, and cardiovascular conditions, as well as to explore gene–environment interactions in the Qatari population.
In this article we describe the rationale, methodology, and infrastructure underpinning the QTR, positioning it as a comprehensive resource for behavioral, epidemiological, and molecular research in both regional and international contexts.
Ethical Considerations
Ethical approval for the QTR study was obtained from the Institutional Review Board of Qatar University (QU-IRB 164/2024-EM) and QPHI (QF-QBB-RES-ACC-00084). All participants provide written informed consent (or assent, in the case of minors). Personally identifiable information is removed from all samples and datasets. Access to data is restricted to authorized personnel only, and all digital records are stored securely, with the possibility of offering controlled data access for external researchers in the future and upon approval. Data sharing and analysis follow the protocols established by QU and QPHI for confidentiality. All study documents, including the collaboration agreement with QPHI, were finalized prior to participant recruitment.
Post recruitment, participants will have a follow-up appointment to receive feedback on their medical examination results, and in case of abnormal findings, participants will be referred to HMC for further investigation according to the QPHI referral program. With participants’ explicit consent, they may be contacted to be informed of genetic variants that are considered medically actionable and relevant to their health or disease risk, particularly where preventive measures, screening, or available treatments may help reduce risk or improve outcomes. Before any genomic research result is used to inform the management of a health condition, it will be validated in a clinically accredited laboratory. In addition, participants may be contacted to receive a personalized genomic report related to wellness and lifestyle.
Study Design and Setting
The QTR is designed as a prospective longitudinal cohort study aimed at establishing the first twin registry in Qatar and the Arab world. It was established and granted by Qatar University in collaboration with QPHI. The QPHI biobank (Al Thani et al., Reference Al Thani, Fthenou, Paparrodopoulos, Al Marri, Shi, Qafoud and Afifi2019) provides the clinical and phenotypic data infrastructure as well as supporting whole-genome sequencing and genomic analysis (Mbarek et al., Reference Mbarek, Devadoss Gandhi, Selvaraj, Al-Muftah, Badji, Al-Sarraj, Saad, Darwish, Alvi, Fadl, Yasin, Alkuwari, Razali, Aamer, Abbaszadeh, Ahmed, Mokrab, Suhre, Albagha and Althani2022).
The integration of QTR with QPHI provides a unique foundation for comprehensive data collection and multiomics research. Through linkage with QPHI biobank, biological samples (e.g., blood and urine) and extensive clinical and lifestyle data are collected following standardized national protocols, ensuring high data quality and long-term sample storage. QPHI enables whole-genome sequencing of QTR participants and supports advanced genomic analyses within Qatar’s secure biomedical data framework. This interconnected infrastructure enhances the registry’s capacity to investigate the genetic and environmental factors underlying complex diseases, ensuring its long-term sustainability. Figure 2 illustrates the data flow and integration across QTR and QPHI.
Integration and data flow between the Qatar Twin Registry (QTR), Qatar University (QU), and the Qatar Precision Health Institute (QPHI). The figure illustrates study initiation, participant recruitment, and multisource data linkage between phenotypic, biospecimen, and genomic data stored at separate entities.
For the pilot phase of QTR, the target sample is 100 to 250 twin pairs. This estimate is based on classical twin power analyses for detecting heritability in complex traits with high genetic contributions, such as obesity (40–70%; Loos & Yeo, Reference Loos and Yeo2022), type 2 diabetes (30–70%; DeForest & Majithia, Reference DeForest and Majithia2022), and hypertension (30–70%; Doris, Reference Doris2011), assuming α = 0.05, 80% power, equal numbers of MZ and DZ pairs, and a missing data rate < 5%. Inclusion of nontwin siblings increases statistical power and allows for more flexible extended twin models (Posthuma & Boomsma, Reference Posthuma and Boomsma2000). The pilot recruitment phase is expected to be completed over approximately three years depending on recruitment rates and participant engagement. In addition, the availability of whole-genome sequence (WGS) data in QTR strengthens the classical twin design. While MZ twins are often assumed to be genetically identical, high-depth sequencing reveals rare postzygotic mutations and structural variations that distinguish MZ co-twins, enabling investigations of somatic mosaicism and within-pair genetic differences (Jonsson et al., Reference Jonsson, Magnusdottir, Eggertsson, Stefansson, Arnadottir, Eiriksson, Zink, Helgason, Jonsdottir, Gylfason, Jonasdottir, Jonasdottir, Beyter, Steingrimsdottir, Norddahl, Magnusson, Masson, Halldorsson, Thorsteinsdottir and Stefansson2021; Ouwens et al., Reference Ouwens, Jansen, Tolhuis, Slagboom, Penninx and Boomsma2018). This provides unique opportunities to study gene–environment interaction and phenotypic discordance in MZ pairs.
Qatar Precision Health Institute
The establishment of the QTR has leveraged Qatar’s robust and well-established national infrastructure, though QPHI (https://www.qphi.org.qa/).
QPHI biobank was established in 2012 as a national prospective cohort study in Qatar. It collects extensive data from Qatari nationals and long-term residents through detailed questionnaires, clinical imaging, omics analyses, and biological samples. The comprehensive dataset enables researchers to investigate the relationship between genetic and environmental factors in the development of diseases (Al Thani et al., Reference Al Thani, Fthenou, Paparrodopoulos, Al Marri, Shi, Qafoud and Afifi2019).
The QPHI genomic program, launched in 2015, is a national, population-based research initiative aimed at understanding the genetic makeup of the Qatari and broader Arab populations. The program generates large-scale WGS data and integrates it with the extensive phenotypic and clinical data collected by QPHI biobank. One of the primary goals is to create a population-specific reference genome and facilitate the integration of precision medicine into Qatar’s healthcare system (Elfatih et al., Reference Elfatih, Mifsud, Syed, Badii, Mbarek, Abbaszadeh, Consortium, Estivill, Management and Ismail2021; Razali et al., Reference Razali, Rodriguez-Flores, Ghorbani, Naeem, Aamer, Aliyev, Jubran, Clark, Fakhro and Mokrab2021). The value of the program as a resource has already been demonstrated in several milestone publications: for example, a large-scale WGS study of 6218 Qatari participants (later replicated in 7768) identified 281 variant–trait associations across 45 clinically relevant traits (Thareja et al., Reference Thareja, Al-Sarraj, Belkadi, Almotawa, Suhre and Albagha2021). Additionally, phase 1 sequencing of 6047 Qataris revealed over 88 million variants (≈approximately 24 million novel), highlighting the unique genetic architecture of the Qatari population (Mbarek et al., Reference Mbarek, Devadoss Gandhi, Selvaraj, Al-Muftah, Badji, Al-Sarraj, Saad, Darwish, Alvi, Fadl, Yasin, Alkuwari, Razali, Aamer, Abbaszadeh, Ahmed, Mokrab, Suhre, Albagha and Althani2022).
Participants
Eligibility criteria
Eligible participants include MZ and DZ twins, higher-order multiples, and their first-degree relatives, including parents, full siblings, and offsprings, in addition to half-siblings. Inclusion criteria are as follows: (1) Qatari nationals or residents; (2) male or female; (3) children or adults; and (4) naturally conceived or conceived through assisted reproductive technologies (ART). There are no exclusions based on phenotype or disease status. Individuals who are unable to provide informed consent due to medical or language barriers (i.e., non-Arabic or non-English speakers) are excluded. Participation in this study is voluntary.
Identification of Potential Participants
Eligible participants for the QTR are identified through both prospective and retrospective approaches.
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• The prospective approach involves community-based outreach efforts such as awareness campaigns conducted through universities, schools, social media platforms, and public events. These activities are designed to engage the public and encourage self-identification and registration by twins/multiples and their families. Qatar University plays a crucial role in participant identification by providing physical spaces at various locations across the university for QTR promotion and outreach campaigns, which commenced in December 2024.
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• The retrospective approach involves reviewing existing QPHI records to identify individuals who are already enrolled and confirmed to be twins or higher-order multiples. These individuals are then contacted for potential inclusion in the QTR.
Outreach of QTR
To facilitate recruitment, the QTR research team developed a multi-platform outreach strategy. In addition, advertisement materials, such as flyers and an introductory video, were posted regularly at QPHI.
The official social media accounts for QTR were created on:
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• Twitter/X: https://x.com/twinregistryQtr
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• Instagram: https://www.instagram.com/qatar_twinregistry/
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• Facebook: https://www.facebook.com/profile.php?id=61551794506613
Through these outreach activities, interested individuals are introduced to the study’s purpose and procedures and invited to register their contact information through: https://docs.google.com/forms/d/1udCeEFnevdrsN_6keSJZ9LpmdlxW3RsmTsHJfxTSo_8/edit for participation.
Recruitment for QTR follows two approaches.
Clinic-based recruitment at QTR recruiting clinics in the QPHI biobank. This approach focuses on recruiting adult twins and multiples and their first-degree adult relatives. This phase is currently underway and utilizes the well-equipped clinics and well-optimized protocols for recruiting adult participants at QBB (Figure 3). Participants undergo a full assessment (Al Thani et al., Reference Al Thani, Fthenou, Paparrodopoulos, Al Marri, Shi, Qafoud and Afifi2019), which includes: (1) Comprehensive QBB questionnaires, including Main Questionnaire, Diet Questionnaire, Short Form Health Survey (SF-36), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and a nurse-administered interview; (2) Clinical measurements, including height, weight, body composition (Tanita), iDXA scans, ECG, carotid ultrasound, spirometry, grip strength, and treadmill fitness tests; (3) Biospecimen collection, including blood (up to 70 mL in clinic), urine, stool, and buccal swabs.
Clinic-based recruitment workflow for the Qatar Twin Registry (QTR) at Qatar Precision Health Institute (QPHI).
Figure 3. Long description
A flowchart illustrating the clinic-based recruitment workflow for the Qatar Twin Registry at Qatar Precision Health Institute. The process begins with clinic-based recruitment at QPHI, targeting adult twins, multiples, and first-degree adult relatives. The flowchart is divided into three main sections: Questionnaires, Clinical Measurements, and Biospecimen Collection. The Questionnaires section includes the Main Questionnaire, Diet Questionnaire, SF-36, WOMAC, and Nurse Interview. The Clinical Measurements section involves height/weight, body composition, IDXA scans, ECG, carotid ultrasound, spirometry, sprimetry, and grip strength. The Biospecimen Collection section includes blood (70 mL), urine, stool, and buccal swabs. The flowchart also indicates the integration of twin-specific questionnaires and registration relatedness questionnaires, which cover family relationships, demographics, and contact information, and are integrated with QPHI standard operating procedures.
All QPHI’s standard operating procedures (SOPs) and instruments were reviewed to ensure alignment with the specific goals of QTR. While QTR adopted QPHI biobank’s SOPs for biospecimen collection, participant recruitment, and imaging, necessary adaptations were made to tailor them for twin research. These include the integration of two additional twin-specific questionnaires specifically developed and incorporated into the QTR protocol.
A Registration Relatedness Questionnaire was developed to capture detailed family and pedigree relationships. It collects: (1) Twins or multiples status of the participant, their siblings, parents, and offspring and as well as parental relatedness and/or consanguinity; (2) Basic demographic and contact information for each family member (QID, name, date of birth, sex, contact availability); (3) Number and distribution of twins and/or multiples within the family. These data support the construction of multigeneration family pedigrees, facilitates recruitment of additional family members, and enables analyses of heritability and familial clustering.
The Qatar Twin Registry Survey (QTR survey) was designed to gather detailed biological, psychosocial, and lifestyle data from twins/multiples, as well as their parental relatedness or consanguinity, and their families. This survey was adapted and further modified from surveys developed by the Netherlands Twin Registry (e.g., Willemsen et al., Reference Willemsen, de Geus, Bartels, van Beijsterveldt, Brooks, Estourgie-van Burk, Fugman, Hoekstra, Hottenga and Kluft2010). Key domains include: (1) Demographics, including age, sex, nationality, education, marital status, and living arrangements; (2) Family and twin structure, including Twin status, zygosity indicators, and consanguinity; (3) Prenatal/perinatal history, including gestational age, conception method, birth order, delivery mode, placental data. This information enables the consideration of assisted reproductive technologies as a relevant variable in downstream analyses; (4) Developmental milestones, including puberty timing, growth patterns, and handedness; (5) Health history, including chronic conditions, medication use, and medical consultations; (6) Behavioral and lifestyle factors, including sleep habits, sports, diet, transport, and daily activities; (7) Mental health and wellbeing, including life satisfaction, contact with mental health services; (8) Eating behaviors, including dieting patterns, body image perception, eating habits; (9) Zygosity and similarity, including physical resemblance, shared clothing, school environments; (10) Family background, including parental age, education, and sibling data.
This instrument enables in-depth exploration of twin-specific research topics, including psychosocial development, gene-environment interactions, and behavioral traits. Participation through this approach typically takes around three hours for each participant.
Recruitment metrics, including number of participants contacted, enrolled, and response rates, are continuously monitored to evaluate feasibility and optimize outreach strategies.
Home visits. The second approach is a home-visit, which allows the recruitment of both children and adults, including those unable to attend their appointments at QTR recruiting clinics within QBB. During home visits or community campaigns, a trained QTR research coordinator introduces the study objectives and procedures to eligible participants, followed by obtaining informed consent. To maintain privacy, the team requests the use of a designated private area within the home for the consent process and data and sample collection.
Participants complete the same comprehensive questionnaires administered at QTR-QPHI biobank facility, covering sociodemographic, health, lifestyle, and twin-related information. Due to equipment limitations, a basic set of clinical measurements is performed during home visits. These include basic physical assessments such as weight, height, and body composition (using portable analyzers such as Tanita devices), along with documentation of demographics, family history, and pedigree information.
Regarding biospecimen collection, a reduced volume of blood (up to 44 mL, adjusted according to the participant’s age and weight) is collected during home visits. Additionally, buccal swab samples are obtained for DNA isolation. Unlike the clinic-based assessments, urine and stool samples are not collected during home visits. Participation through this approach takes around 2 hours for each participant.
The majority of participants are expected to be recruited through clinic-based visits at the QPHI biobank facility, while home visits represent a complementary strategy to enhance accessibility, particularly for children and individuals unable to attend clinic appointments. While differences between clinic-based and home-based recruitment may introduce potential selection bias, the inclusion of both approaches is intended to improve representativeness and inclusivity of the study population across different age groups and accessibility levels.
Sample Handling
All samples are processed and stored at QPHI following standardized protocols. Serum is used for biochemical assays, and the buffy coat is used for DNA extraction. All samples are anonymized and coded.
Genotyping and Zygosity Determination
WGS is performed through QPHI using the Illumina NovaSeq platform, with standard downstream quality control and variant calling pipelines. Zygosity will be determined using genomewide allele-sharing estimates in PLINK based on the pairwise proportion of alleles shared (π-hat), where MZ twins are expected to show π-hat ≈ 1 and DZ twins ≈ 0.5. Identity-by-descent (IBD) metrics derived from a genetic relationship matrix will be used to confirm zygosity, assess kinship, and evaluate population structure.
The timeframe from participant enrollment to WGS completion and zygosity confirmation is dependent on sequencing and data-processing workflows within the QPHI Genome Program. Generally, the samples will be sent for whole genome sequencing in batches of 50 samples.
Zygosity information is generated as part of the research workflow. At the current stage, return of individual-level genomic results, including zygosity status, is governed by institutional policies and may be incorporated into future phases of the registry.
Questionnaire-based indicators of twin zygosity may be used for preliminary presumptive classification of zygosity during early recruitment stages; however, conclusive zygosity determination will rely on genomic confirmation when available.
These genomic data will support classical twin modeling and enable downstream genomewide association studies (GWAS) and future epigenomewide association studies (EWAS).
Recruitment Progress
Outreach through various social media platforms, campaigns, and community activities has resulted in a growing pool of registered twins and multiples across Qatar. Public engagement began with online registration forms and awareness events organized at Qatar University and QPHI Biobank, collectively enhancing visibility and interest in participation.
Active in-clinic recruitment at QPHI Biobank commenced in June 2025, marking the transition from outreach to direct participant enrollment. As of April 2026, a total of 48 participants have been successfully enrolled in the study, including twin pairs and family members.
Through outreach activities, 256 individuals registered their interest in participation and were all contacted. Of these, 88 were confirmed eligible for the current phase (i.e., adults and twins or twin relatives). Among eligible individuals, 72 agreed to participate while 16 declined, corresponding to an acceptance rate of 81%. Recruitment remains ongoing, with continued expansion through digital channels to reach a broader segment of the Qatari population.
Discussion
Significance and Novelty
Individuals of Arab ancestry account for fewer than 0.2 % of participants in published genomewide association studies (Bhattacharya et al., Reference Bhattacharya, Chen, Shim, Kuwahara, Gao, Alkuraya and Fahed2023). Therefore, QTR represents an important step in bridging this gap. QTR incorporates an Arab population characterized by high rates of consanguinity and inbreeding, which are common in many Arab communities due to cultural and social practices. These factors contribute to a unique genetic architecture of diseases and phenotypes, including increased homozygosity and the enrichment of rare recessive alleles that may not be detectable in more genetically diverse populations (Al-Gazali & Hamamy, Reference Al-Gazali and Hamamy2014; Bhattacharya et al., Reference Bhattacharya, Chen, Shim, Kuwahara, Gao, Alkuraya and Fahed2023; Tadmouri et al., Reference Tadmouri, Nair, Obeid, Al Ali, Al Khaja and Hamamy2009). By including this population in the global twin research framework, QTR enables new investigations into heritability, gene–environment interactions, and population-specific disease mechanisms (Manolio et al., Reference Manolio, Collins, Cox, Goldstein, Hindorff, Hunter, McCarthy, Ramos, Cardon and Chakravarti2009; Sirugo et al., Reference Sirugo, Williams and Tishkoff2019).
The inclusion of twins conceived through assisted reproductive technology (ART) represents an important aspect of the QTR design and will contribute to research on the genetic spectrum of female fertility, which appears to exist on a continuum, with anovulation or infertility at one end and DZ twinning at the other (Hubers et al., Reference Hubers, Page, Pool, Mbarek, Lambalk, Mijatovic, Ligthart, van Dongen, Håberg, Corfield, Beck, Ehli, Martin, Willemsen, Harris, Hottenga and Boomsma2025). Information on conception methods is systematically collected, allowing future analyses to account for ART status when investigating genetic and environmental contributions to complex traits.
Biobank Integration Benefits
QTR is the first twin registry in the Arab world, established by Qatar University in collaboration with QPHI. The registry benefits from an existing population-based biobank and a large-scale whole-genome sequencing infrastructure at QPHI. In addition to recruiting adult participants through the QTR recruiting clinic at QPHI biobank, we introduced a home-visit protocol to facilitate the recruitment of children, multiples, and their relatives.
A key advantage of integrating with an established national biobank is the ability to utilize an existing infrastructure, which significantly reduces the time and resources required to establish a new registry. QBB, with over a decade of operational experience, provided SOPs for participant recruitment, biospecimen collection and processing, and imaging. QTR adopted these SOPs, adapting them to meet the specific requirements of twin research. This ensured methodological consistency while enabling us to benefit from QPHI’s validated workflows, trained personnel, and logistical capacity.
Additionally, integrating with QPHI has a significant impact on community engagement. QPHI has already recruited 42,000 participants and includes a specific question on twin status in its survey (Al Thani et al., Reference Al Thani, Fthenou, Paparrodopoulos, Al Marri, Shi, Qafoud and Afifi2019). This enables the retrospective identification of twins already registered in the biobank and their linkage to QTR, thereby expanding the registry’s coverage.
Several international twin registries have successfully integrated with biobank infrastructures, demonstrating the efficiency and research potential of this model. For example, TwinsUK at King’s College London is embedded within the university’s biobank and supports longitudinal phenotyping, imaging, and multiomics analyses in a large volunteer cohort (Hur et al., Reference Hur, Bogl, Ordoñana, Taylor, Hart, Tuvblad, Ystrom, Dalgård, Skytthe and Willemsen2019). The Netherlands Twin Register maintains a biobank that has been connected to phenotypic data collected over several decades (Willemsen et al., Reference Willemsen, de Geus, Bartels, van Beijsterveldt, Brooks, Estourgie-van Burk, Fugman, Hoekstra, Hottenga and Kluft2010). In Sri Lanka, the twin biobank houses more than 3300 DNA and serum samples, collected under rigorous protocols suitable for both clinical and home settings (Jayaweera et al., Reference Jayaweera, Warnakula, Dissanayake, Adikari, Siribaddana, Zavos, Rijsdijk, Zunszain, Pariante and Glozier2020). The Swedish Twin Registry integrates biobanking with nationwide health register linkages, enabling comprehensive population-based studies (Lichtenstein et al., Reference Lichtenstein, Sullivan, Cnattingius, Gatz, Johansson, Carlström, Björk, Svartengren, Wolk and Klareskog2006), while the Finnish FinnGen project demonstrates how large-scale population biobanking linked to national health records can further enhance genomic discovery at scale (Kurki et al., Reference Kurki, Karjalainen, Palta, Sipilä, Kristiansson, Donner, Reeve, Laivuori, Aavikko and Kaunisto2022). These examples highlight the strategic advantages of QTR’s integration with QPHI, combining existing biobank and genomic resources to facilitate high-quality, large-scale twin research in an underrepresented population. Additionally, our home-visit recruitment model for children and their relatives further increases sample size and demographic diversity.
Challenges and Lessons
Several challenges emerged during the initial implementation of the Qatar Twin Registry. First, the process of establishing formal agreements and obtaining IRB approvals from the contributing institutions required some time, given the project’s large scope and novelty within the region. Implementing modifications to the pre-existing QPHI protocols also required substantial time and justification. Multiple user acceptance testing (UAT) sessions were conducted with the project team to verify, refine, and confirm that all system changes were correctly implemented and thoroughly tested.
Second, the current infrastructure at QPHI is designed primarily for adult participants. Although many parents have expressed interest in enrolling their children, the lack of ready clinics for children has limited recruitment and reduced participant diversity at this early stage. To address this, we implemented home-visit protocols, which are expected to improve accessibility and expand participation in future phases of the study. While the data collected through home visits is less comprehensive compared to data obtained at QPHI facilities, it still meets the core requirements for sample and data collection. The use of both clinic-based, and home-visit recruitment strategies may introduce selection bias; however, this approach was intentionally implemented to maximize inclusivity and capture a broader representation of the population, particularly among pediatric participants and families with limited access to clinic-based services.
Cultural and social factors may influence participation in twin research within the Qatari population, as well as in research more broadly. Family-centered decision-making, cultural perceptions of research, and preferences regarding privacy may all affect participant engagement. To address this, recruitment strategies were designed to be culturally sensitive, including the use of Arabic-language materials and community-based outreach initiatives.
Conclusion
The establishment of the QTR marks a significant milestone for genetic and epidemiological research in the Arab world. As the first twin registry in the region and one of only two in the Middle East and North Africa, QTR addresses a critical gap in global twin resources. Its design within QPHI demonstrates how benefiting from existing infrastructure can accelerate the development of high-impact population resources.
By integrating and linking comprehensive phenotyping, longitudinal follow-up, and genomic analysis, QTR provides a powerful platform for studying heritability, gene–environment interactions, and complex disease risk in a population characterized by high rates of consanguinity.
Although still in its early stages, QTR has successfully launched. Early engagement metrics suggest strong public interest. Planned future expansions, including recruitment of children and home visits, will enhance the depth and reach of the registry.
QTR will contribute to the international twin research community, cross-population meta-analyses, and regional public health research. It serves as a strong model for other countries in the Arab world seeking to build biobank-linked twin registries that are both scientifically strong and practically efficient.
Acknowledgments
The authors would like to thank Qatar University for funding the establishment of the QTR. Special appreciation is extended to the teams at QPHI for their invaluable collaboration and technical support in participant recruitment and data management. Finally, sincere gratitude is expressed to all twins, multiples, and their families who generously volunteered to participate in the registry. We also thank Qatar National Library for providing Open Access funding for this article.
Financial support
This work was supported by Qatar University under grant number QUCG-CHS-23/24-201.
Conflict of interest
The authors declare no conflicts of interest related to the study.
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