A comparison of the allelic frequencies of ten DNA polymorphisms associated with factor VIII and factor IX genes in Thai and Western European populations

National strategic advocacy to manage patients with inherited bleeding disorders in low and lower-middle income countries

INTRODUCTION

Inherited bleeding disorders (IBDs) including hemophilia, von Willebrand disease, platelet disorders, mucocutaneous bleeding disorders and coagulation factor deficiencies are rarely found and under-recognized in low and lower-middle-income countries. Some patients succumbed to serious bleeding without diagnosis and treatment during childhood.

AREA COVERED

Diagnosis, management, and prevention should be integrated into the existing health care system. Although some countries have not implemented appropriate health care infrastructure, an initiative plan should be set up by cooperation of experienced experts and health care providers. Identification of patients with IBDs should be started in the antenatal setting to search for females at risk of carrier state. The investigations include bleeding assessment, mixing venous clotting time, coagulogram, coagulation factor assay and mutation detection. Genotypic analysis is helpful for confirming the definite diagnosis, carrier detection as well as prenatal diagnosis for females at risk of bearing an offspring with severe bleeding manifestations. Management involves replacement therapy ranging from blood component to virus-inactivated factor concentrate. Appropriate research is an essential backbone for improving patients' care.

EXPERT OPINION

Effective national strategic advocacy to manage patients with IBDs requires intensive collaboration among policy makers, health care providers, patients, and family members.

Three-Decade Successive Establishment of Care for Women/Girls from Families with Haemophilia

Objective

The study aimed to report a 3-decade successive establishment of care for women/girls from families with haemophilia.

Methods

A retrospective analysis was conducted on 462 women/girls from 243 families from 1987 to 2021.

Results

Combining phenotypic analysis of coagulation factor and genotypic analysis of either linkage analysis or mutation detection confirmed the status of all obligate haemophilia carriers (A118, B19). For potential carrier, 159 proven carriers (A130, B29) and 146 noncarrier status (A126, B20) were diagnosed except 20 potential carriers (A16, B4). Only 54 prenatal diagnoses were requested resulting in normal males (n = 21), males with haemophilia A (n = 12) and females with either normal or carrier status (n = 21). Additionally, 40 women/girls with haemophilia carrier received a diagnosis of severe haemophilia A with Turner’s syndrome (n = 2) and mild haemophilia (A31, B7). The skewed X-chromosome inactivation of the nonmutant factor VIII/IX carrying X-chromosome of 8% (2/25) was found in mild haemophilia. Factor concentrate and desmopressin are prescribed for these affected women/girls. The response of women/girls with either haemophilia carrier or haemophilia was amazement with their religious beliefs and cultural acceptance.

Conclusion

Appropriate care for women/girls from families with haemophilia concerning diagnosis and management of haemophilia and carrier has been successively established.

Prenatal diagnosis for haemophilia: the Thai experience

BACKGROUND

Haemophilia is a lifelong X-linked recessive inherited bleeding disorder. Since the haemophilia management in economically less-developed countries is inadequately provided, prevention of new cases of haemophilia is essentially required.

SUBJECTS AND METHODS

A total of 42 pregnancies in 37 women at risk for severe and moderate haemophilia (A = 33, B = 4) were enrolled. The prenatal diagnostic (PND) procedure was performed in 32 women, while 10 women refused further PND procedure after knowing their foetuses were female (n = 8) and male (n = 2). The foetal specimen was obtained through chorionic villus sampling (n = 14), amniocentesis (n = 1) and cordocentesis (n = 17). The status of haemophilia was determined using informative RFLP markers and inversion of intron 22 of the F8 gene, and/or foetal FVIII:C or FIX:C.

RESULTS

The final diagnosis revealed normal males (n = 18), haemophilia A males (n = 9), normal females (n = 3) and haemophilia A carrier females (n = 2). All women with affected haemophilia sons requested to terminate their pregnancies except one woman. One of 32 pregnancies (3.1%) had spontaneous abortion. At follow-up after birth, the PND was accurately confirmed in one haemophilia A male, three normal females and two carrier females by laboratory testing, and 18 unaffected normal males by history taking of no bleeding manifestations. However, 10 women who continued their pregnancies after knowing foetal sex turned out to have two haemophilia A males, one normal female, one haemophilia A carrier female and six normal or carrier females.

CONCLUSION

The PND of haemophilia could be accurately determined but it was not well accepted by all couples at risk.

Screening for hemophilia A carriers: utility of PCR-RFLP--based polymorphism analysis

Health schemes are promoting application of molecular diagnosis and screening in peripheral diagnostics labs. Intragenic restriction fragment length polymorphisms in the intron 18 (BclI), intron 19 (HindIII), and intron 22 (XbaI) of the Factor VIII gene were studied in 100 patients with hemophilia A and their relatives at risk from different regions of north India. For Bcl I, HindIII, and XbaI, the positive allele frequency was 0.57, 0.38, and 0.43, respectively, and heterozygosity was 0.54, 0.49, 0.41, respectively, whereas the heterozygosity in terms of informativity of the above markers was 53% for BclI, 44% for HindIII, and 34% for XbaI. Combined informativity of these markers was 77%. Review of Indian and world literature shows a marked variation in the informativity of polymorphic sites. Screening for carriers forms the baseline for prevention of hemophilia A. Polymerase chain reaction-restriction fragment length polymorphism is a low-cost procedure, efficient in the north Indian population.

Essential issues of laboratory investigation for patients with haemophilia and bleeding disorders

Apart from history-taking and physical examination, laboratory investigation is one of the essential issues for the definite diagnosis of haemophilia and bleeding disorders. The limited resources of medical personnel, equipment and reagents should be shared among several departments in the hospital, especially for serving patients with common genetic diseases such as thalassemia and haemoglobinopathies. Medical personnel require appropriate training to expand their skills in laboratory techniques. Laboratory procedures can be created, modified and simplified using locally produced and shared equipment. Molecular genetic studies can also be set up at different levels of hospital service using simple, rapid and low-cost methods. Finally, a system of periodic external quality control will guarantee the accuracy of laboratory results.

Allele frequencies of two polymorphisms associated with the factor IX gene in Iranian population

Indirect genetic diagnosis using polymorphic DNA markers can be useful in large-scale screening programs, which is technically simpler, more rapid and amenable. The main objective of this study was to test the informativeness of two common intragenic markers (TaqI and XmnI) in Iranian haemophilia B families to detect the carriers by using a strategy that would be accurate and informative, yet less expensive compared to direct mutation analysis. The efficacy of these sites has been examined in 50 unrelated Iranian haemophilia B families and 50 normal females. The method used was polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP), which is economical and the enzymes XmnI and TaqI are cheap enough to be accessible in most of laboratories in developing countries. Our results show that 25% of X-chromosomes had the restriction site for TaqI enzyme. The XmnI site was 21%. The heterozygosity rates for TaqI and XmnI polymorphisms were 37% and 38%, respectively. Using the two polymorphisms together, the informative rate reached 46%. Taking advantage of TaqI and XmnI polymorphisms, carrier detection was performed for seven females with unknown status in five haemophilia B families (including one large extended family) with positive history. Six of the girls were normal and one was haemophilia B carrier. Therefore, carrier detection might be possible for informative Iranian haemophilia B families in the familial cases. Additionally, similarities in term of heterozygosity rates for these two polymorphic sites were seen between some European and Iranian populations.

Haemophilia B: from molecular diagnosis to gene therapy

Thanks to its typical expression, haemophilia can be identified in writings from the second century AD. Haemophilia B, an X-linked recessive bleeding disorder due to factor IX (FIX) deficiency, has an incidence of about 1:30,000 live male births. The factor 9 (F9) gene was mapped in 1984 on Xq27.1. Haemophilia is diagnosed from prothrombin time, activated partial thromboplastin time, and FIX levels. Carrier females are usually asymptomatic and must be identified only with molecular analysis. Linkage analysis of F9 polymorphisms is rapid and inexpensive but limited by non-informative families, recombinant events, and the high incidence of germline mutations; thus, various procedures have been used for the direct scan of F9 mutations. We set up a novel denaturing high performance liquid chromatographic procedure to scan the F9 gene. This rapid, reproducible procedure detected F9 mutations in 100% of a preliminary cohort of 18 haemophilia B patients. Parallel to the development of more efficient diagnostic tools, the life expectancy and reproductive fitness of haemophilic patients have greatly improved and will continue to improve thanks to the use of less immunogenic recombinant FIX. Hopefully, new approaches based on gene therapy now being evaluated in clinical trials will revolutionise haemophilia B treatment.

Management of haemophilia in the developing world

The problems with management of haemophilia in developing countries are poor awareness, inadequate diagnostic facilities and scarce factor concentrates for therapy. The priorities in establishing services for haemophilia include training care providers, setting up care centres, initiating a registry, educating affected people and their families about the condition, providing low-cost factor concentrates, improving social awareness and developing a comprehensive care team. A coagulation laboratory capable of reliably performing clotting times with correction studies using normal pooled, FVIII and FIX deficient patient plasma and factor assay is most essential for diagnosis. More advanced centralized laboratories are also needed. Molecular biology techniques for mutation detection and gene tracking should be established in each country for accurate carrier detection and antenatal diagnosis. Different models of haemophilia care exists. In India, there is no support from the government. Services, including import of factor concentrates, are organized by the Haemophilia Federation of India, with support from other institutions. Haemophilia is managed with minimal replacement therapy (about 2000 i.u./PWH/year). In Malaysia, where the system is fully supported by the government, facilities are available at all public hospitals and moderate levels of factor concentrates are available 'on-demand' (about 11,000 i.u./PWH/year) at the hospitals. Haemophilia care in South Africa is provided through major public hospitals. Intermediate purity factor concentrates are locally produced (about 12,000 i.u./PWH/year) at low cost. The combined experience in the developing world in providing haemophilia services should be used to define standards for care and set achievable goals.