Detección de portadores del rasgo drepanocítico en una muestra de población de Maracay y su zona metropolitana / Detection of sickle cell trait carriers in a population sample of Maracay and its Metropolitan area

La Anemia drepanocítica es una enfermedad genética con patrón de herencia autosómico recesivo, caracterizada por la presencia de eritrocitos en forma de hoz, los cuales no pueden pasar eficientemente por los capilares provocando vaso-oclusión, daños en tejidos y crisis dolorosas. En el Estado Aragua se ha reportado una frecuencia relativamente alta de pacientes drepanocíticos y portadores del rasgo drepanocítico, quienes pueden ser sintomáticos en condiciones de hipoxia. El objetivo del trabajo consistió en detectar portadores del rasgo drepanocítico en una muestra de 200 individuos sin relación de parentesco y sin síntomas de anemia drepanocítica, habitantes de Maracay y su zona Metropolitana, estado Aragua; para dar información genético-patológica pertinente a los portadores y sus familias. Una vez obtenido el consentimiento informado, se tomó una muestra de sangre para detectar células drepanocíticas mediante la prueba de Metabisulfito de Sodio y el diagnóstico se confirmó con un ensayo de Reacción en Cadena de la Polimerasa y posterior digestión con la enzima Bsu 36 I. Se encontraron 13 portadores del rasgo drepanocítico (6,5%). Al incluir 20 familiares de 6 de estos portadores sanos, se obtuvo una frecuencia de 45%. Se dio información genético-patológica al grupo familiar, con énfasis en la prevención a la exposición de factores de riesgo y la prevención de la producción del nacimiento de homocigotos afectados. Estos resultados alertan sobre la necesidad de establecer programas de detección y educación de portadores del rasgo drepanocítico para prevenir complicaciones de salud en estas personas.

The sickle cell disease is a genetic disease, with autosomal recessive inheritance pattern, characterized by the presence of sickleshaped red blood cells, which cannot pass efficiently through the capillaries causing vaso-occlusion, tissue damage and painful crisis. In Aragua State it has been reported a relatively high frequency of sickle cell patients and healthy carriers of sickle cell trait, who may be symptomatic under conditions of hypoxia. The aim of this study was to detect carriers of sickle cell trait in a sample of 200 nonrelated individuals without symptoms of sickle cell disease, habitants of Maracay and its metropolitan area, Aragua state, to provide genetic-pathological information relevant to families of healthy carriers identified. After obtaining informed consent, a sample of peripheral blood was taken to detect sickle cell through sodium metabisulfite test, the diagnosis was confirmed by a Polymerase Chain Reaction test and subsequent digestion by Bsu 36 I enzyme. Thirteen carriers of sickle cell trait were found, (6.5%). By including 20 relatives of 6 healthy carriers a frequency of 45% was obtained. Pathological genetic information to the family was provided with emphasis on prevention of exposure to risk factors and prevention of production of homozygous affected birth. These results highlight the need to establish detection and education of sickle cell trait carriers to prevent health complications in these individuals.

Utility of MLPA in mutation analysis and carrier detection for Duchenne muscular dystrophy.

CONTEXT: Multiplex ligation probe amplification (MLPA) is a new technique to identify deletions and duplications and can evaluate all 79 exons in dystrophin gene in patients with Duchenne muscular dystrophy (DMD). Being semi-quantitative, MLPA is also effective in detecting duplications and carrier testing of females; both of which cannot be done using multiplex PCR. It has found applications in diagnostics of many genetic disorders. AIM: To study the utility of MLPA in diagnosis and carrier detection for DMD. MATERIALS AND METHODS: Mutation analysis and carrier detection was done by multiplex PCR and MLPA and the results were compared. RESULTS AND CONCLUSIONS: We present data showing utility of MLPA in identifying mutations in cases with DMD/BMD. In the present study using MLPA, we identified mutations in additional 5.6% cases of DMD in whom multiplex PCR was not able to detect intragenic deletions. In addition, MLPA also correctly confirmed carrier status of two obligate carriers and revealed carrier status in 6 of 8 mothers of sporadic cases.

Ethical issues in genetic counselling with special reference to haemoglobinopathies.

Genetic counselling is provided in places where genetic tests are carried out. The process involves pre-test counselling as well as post-test counselling to enable the individuals to face the situation and take appropriate decisions with the right frame of mind. Major ethical principles which govern the attitudes and actions of counsellors include: respect for patient autonomy, non-maleficence, beneficence, or taking action to help benefit others and prevent harm, both physical and mental, and justice, which requires that services be distributed fairly to those in need. Other moral issues include veracity, the duty to disclose information or to be truthful, and respect for patient confidentiality. Nondirective counselling, a hallmark of this profession, is in accordance with the principle of individual autonomy. High prevalence of haemoglobinopathies with availability of good and sensitive carrier detection tests and prenatal diagnostic techniques makes these good candidates for population screening of carriers along with genetic counselling for primary prevention of the disease. Screening of the extended family members of the affected child, high risk communities and general population screening including antenatal women are the main target groups for planning a Haemoglobinopathy control programme. A critical mass of trained genetic counsellors who have understanding of the ethical issues and its appropriate handling with the required sensitivity is needed in India.

As bases moleculares da hemofilia A

As hemofilias são doenças hemorrágicas resultantes da deficiência de fator VIII (hemofilia A) ou de fator IX (hemofilia B) da coagulação, decorrentes de mutações nos genes que codificam os fatores VIII ou IX, respectivamente. A hemofilia A é mais frequente que a hemofilia B e acomete aproximadamente 1:10.000 nascimentos masculinos. A gravidade e frequência dos episódios hemorrágicos está relacionado ao nível residual de atividade de fator VIII presente no plasma e este relaciona-se ao tipo de mutação associada à doença. A clonagem do gene do fator VIII tornou possível o conhecimento das bases moleculares da hemofilia A, sendo hoje conhecidas mais de 1.000 mutações associadas à doença. O conhecimento das bases moleculares da hemofilia A permite uma melhor compreensão da relação genótipo-fenótipo da doença, tomada de condutas clínicas diferenciadas em casos de mutações associadas a um maior risco de desenvolvimento de inibidor, determinação da condição de portadora de hemofilia em mulheres relacionadas aos pacientes, implementação de programa de aconselhamento genético/orientação familiar e melhor compreensão das relações estruturais-funcionais do gene-proteína. Este artigo propõe revisar as bases moleculares da hemofilia A, os métodos laboratoriais utilizados para a caracterização das mutações e as implicações clínicas envolvidas no diagnóstico molecular da hemofilia A.

Hemophilias are bleeding disorders due to deficiency of the blood coagulation factor VIII (hemophilia A) or factor IX (hemophilia B), resulting from mutation on the gene coding for factor VIII or factor IX. Hemophilia A is more frequent than hemophilia B and affects 1:10,000 male newborns. The severity and frequency of hemorrhagic episodes is related to residual activity of factor VIII present in the plasma and relates to the type of mutation associated with the disorder. Cloning of the factor VIII gene has enabled researchers to better understand the molecular basis of hemophilia A, accounting to date, for more than 1,000 mutations associated with the disease. This comprehensive knowledge permits an improved comprehension of the genotype-phenotype relation, establishment of clinical policies when mutations related to higher risk of inhibitors development are known, identification of hemophilia carriers in case of women related to patients, implementation of a program of genetic counseling and discovery of structural-functional relationship between gene-protein. This article aims to review the molecular basis of hemophilia A, laboratory techniques used to characterize mutations and clinical implications involved in the molecular diagnosis of hemophilia A.

The relative research between gene deletion with DMD and carrier screening / 重庆医科大学学报

Objective:To understand the distributional characteristics of dystrophin gene deletion in Chinese population and to search the linkage analysis of STR polymorphisms for DMD gene carriers.Methods:Contrasted with internal standard primer,A multiple PCR system was established according to the multiple sites of DMD exon deletion.The multiple exon deletions were examined in 40 DMD patients;At the same time,6 suspected carriers were detected using the linkage analysis of STR polymorphisms.Results:The thirty-tow of the 40 DMD patients were identified as having gene deletion,In this study,56%,56%,16%DMD patients could be detected in exon 45、48、51 gene deletion,so the three pairs primers could be used as best combination for detecting the gene deletion;six female relatives were diagnosed as carriers of the genes.Conclusion:It is important clinical value of allocating gene mutation sites in Chinese population according to the choosen exons and It is an effective approach to applying the linkage analysis of STR polymorphisms to detect carrier.

Diagnosis of factor VIII gene inversion by PCR in Korean patients with hemophilia A and its application to carrier detection / 대한산부인과학회지

OBJECTIVE: To establish PCR (polymerase chain reaction) method for detecting factor VIII gene inversion (intron 22) causing hemophilia A, and to apply it to carrier detection of hemophilia A. DESIGN: A laboratory analysis MATERIALS AND METHODS: An inversion pattern of the factor VIII gene was analyzed in 130 unrelated Korean patients with hemophilia A and 26 female subjects using PCR. RESULTS: PCR analysis of the factor VIII gene for intron 22 inversion revealed that 91 patients (70%) were negative for the inversion, yielding 12 kb band by PQ primer. And all the other 39 (30%) patients who showed no amplification by PQ primer were positive for the inversion, yielding 11kb band by AQ primer. Among 113 patients with severe hemophilia A, 39 (35%) patients were positive for the inversion. Carrier detection for intron 22 inversion in 26 female subjects was performed, and revealed that 22 cases were carriers and 4 cases were normal female. CONCLUSION: This result suggests that PCR analysis of the inversion within the factor VIII gene is useful in the carrier detection of hemophilia A as well as in identifying hemophilia A patients with intron 22 inversion, in the Korean population.

Molecular diagnosis of hemophilia A and B. Report of five families from Costa Rica

Hemophilia A and B are X-chromosome linked bleeding disorders caused by deficiency of the respective coagulation factor VIII and IX. Affected individuals develop a variable phenotype of hemorrhage caused by a broad range of mutations within the Factor VIII or Factor IX gene. Here, were report the results of the molecular diagnosis in a five Costa Rican families affected with Hemophilia. Methods of indirect and direct molecular diagnosis are applied in three Hemophilia A and two Hemophilia B families from Costa Rica as well as preconditions, practicability and facilities of this diagnosis. In two families with Hemophilia A and both families with Hemophilia B the causative mutation could be detected by Southern blotting, polymerase chain reaction or sequence analysis. One Hemophilia A family could only analyzed by linkage analysis using genomic markers.

Alternate strategies for carrier detection and antenatal diagnosis in haemophilias in developing countries.

Carrier detection and prenatal diagnosis constitute an important component of haemophilia management . Recent advances in molecular biology allows us to use the tools of molecular biology to give such a diagnosis early in the pregnancy with a much higher confidence. Because of lyonisation, diagnosis of a carrier by factor assay is imperfect and hence lacks sensitivity. Molecular diagnosis in such cases is robust.There are several techniques by which this diagnosis can be made.Though the preferred method is to do direct mutation studies, yet the complexities of factor VIII and factor IX genes may not make this approach easy or cost effective. Hence depending on the capability of the laboratory, education status of the family, availability of data through several generations and economic situation of the country, a combination of these techniques need to be adopted for optimum results. These techniques are broadly classified as indirect techniques through linkage analysis or direct detection of affected genes by a combination of screening and sequencing techniques. Occasionally in our country even all the gene based techniques may prove inadequate and we may have to give prenatal diagnosis by antigen and clotting activity assay of the defective factor by cordocentesis between 17-20 weeks of gestation. For any prenatal diagnosis of haemophilia, prior detection of fetal sex either by USG or by molecular technique is necessary to decide whether any further work up is necessary or not? The present article describes various algorithms of carrier detection prenatal diagnosis of haemophilia that was found suitable in our country.

Molecular Genetic Diagnosis of Hemophilia A by Linkage Analysis of XbaI/intron 22 DNA Polymorphism Using PCR / 대한산부인과학회잡지

OBJECTIVE: To set up the methodology for PCR analysis of XbaI/intron 22 polymorphism of the factor VIII gene, and to identify the usefulness of XbaI/intron 22 polymorphism analysis for carrier detection and prenatal diagnosis of hemophilia A in the Korean population. DESIGN: A laboratory analysis. MATERIALS AND METHODS: A XbaI/intron 22 polymorphism of the factor VIII gene was analyzed in 56 unrelated Korean mothers of patients with severe hemophilia A, using polymerase chain reaction. RESULTS: Analysis of XbaI/intron 22 polymorphisms of the factor VIII gene were feasible by PCR method. The expected heterozygosity rates of XbaI/intron 22 polymorphism of the factor VIII gene were 44.8%. Analysis of XbaI/intron 22 polymorphism revealed heterozygous patterns in 22 (39.3%) of 56 mothers studied. Using linkage analysis with XbaI/intron 22 polymorphism, we have attempted one case of carrier detection and two cases of prenatal diagnosis in two families of patients with severe hemophilia A. CONCLUSION: These results suggest that PCR analysis of the XbaI/intron 22 polymorphism within the factor VIII gene is very useful in the carrier detection and prenatal diagnosis of hemophilia A in the Korean population.

Characterization of Mutations in Bruton's Tyrosine Kinase(Btk)Gene from Unrelated 3 X-linked Agammaglobulinemia(XLA) Families in Korea

PURPOSE: X-linked agammaglobulinemia(XLA) is an immunodeficiency caused by abnormalities in Bruton's tyrosine kinase(Btk), and is characterized by a deficiency of peripheral blood B cells. We studied cytoplasmic expression of Btk protein and analyzed the Btk gene in peripheral blood mononuclear cells(PBMC) from three XLA families in Korea. METHODS: Heparinized venous blood samples were collected from four XLA patients and additional family members in three unrelated XLA families. Mononuclear cells were separated from their blood and the intracellular Btk protein was characterized by a flow cytometry. The mutation analysis was performed using direct sequencing. RESULTS: Cytoplasmic expression of Btk protein in monocytes was not detected in the patients with XLA. We observed a novel deletion and two point mutations within introns(intron 1 and intron 18) resulting in alternative splicings. In XLA family 2, a 980 bp deletion(from intron 9+191 T to intron 10-215 C) including exon 10 was found in patient P2. He was the only sporadic case in this study, because his mother and brother showed a normal Btk expression by flow cytometry. CONCLUSION: These identified genetic alterations support the molecular heterogeneity of Btk gene in XLA disease. Additionally, by means of flow cytometric analysis, we diagnosed three hypogammaglobulinemia patients as XLA. Advancements in diagnostic methods has facilitated a prompt and definite diagnosis of this disease.

Characterization of Bruton's Tyrosine Kinase Genetic Mutations in One Korean X-linked Agammaglobulinemia Family

PURPOSE: X-linked agammaglobulinemia(XLA) is an immunodeficiency caused by abnormalities in Bruton's tyrosine kinase(Btk), and is characterized by a deficiency of peripheral blood B cells. We studied the cytoplasmic expression of Btk protein and analyzed the Btk gene in peripheral blood mononuclear cells from two siblings and one cousin with XLA, as well as additional family members. METHODS: Btk protein expression was analyzed by flow cytometry. Isolation of the coding sequence of the Btk gene was performed by amplification using the reverse transcription-polymerase chain reaction(RT-PCR) technique. Sequence alterations were screened by the single-stranded conformation polymorphism(SSCP) method and characterized by standard sequencing protocols. RESULTS: Cytoplasmic expression of Btk protein in monocytes was not detected in three patients with XLA. In addition, Btk protein analysis clearly showed cellular mosaicism in monocytes from four obligate carriers, findings further supported by SSCP. A single base pair mutation(T to C) in Btk-exon three, which encodes the PH domain, was identified in four XLA patients. A diagnostic sequencing analysis was established to detect heterozygotic pattern in 4 carrier females. Furthermore, we found significant clinical heterogeneity in individuals with the same gene mutation. CONCLUSION: The implicating genetic alteration provided valuable clues to the pathogenesis of XLA in Korea and the flow cytometric analysis was suggested as a useful tool for rapid detection of XLA patients and carriers. The present study has identified a genetic mutation in the Btk coding region and demonstrated heterogeneity in clinical manifestations among patients with the same mutation. A flow cytometric analysis was found to be informative in establishing a deficiency of Btk protein in both patients and carriers and is recommended as a frontline procedure in the molecular diagnosis and work-up of XLA.

Protein and Genetic Analysis of Bruton's Tyrosine Kinase(Btk) in Three Korean X-linked gammaglobulinemia(XLA) Families

PURPOSE: Mutations in the Bruton's tyrosine kinase(Btk) gene are responsible for X-linked agammaglobulinemia(XLA), an immunodeficiency caused by a block in B cell differentiation. In this report we characterize the protein expression and genetic mutations of Btk in four Korean patients with three unrelated XLA families. METHODS: The resulting Btk proteins were characterized by a flow cytometry and the mutations were analyzed using single strand conformation polymorphism(SSCP) and direct sequencing. RESULTS: Two deletions, including one novel genetic alteration, and one splicing error, were found in these three XLA families. Along with the identification of mutations, Btk protein analysis using flow cytometry clearly showed cellular mosaicism in monocytes from five obligate carriers, findings consistent with those by SSCP. We attempted to determine the origin of mutation in an XLA family with a novel 4-bp deletion of exon eight, suggesting a germline mutation in this family. In addition, we found some clinical heterogeneities in the affected brothers with the same gene mutation. CONCLUSION: These identified genetic alterations provided valuable clues to the pathogenesis of XLA in Korea. The flow cytometric analysis is suggested as a useful tool for rapid detection of XLA patients and carriers.

Status of Calpain In gene deleted carriers of Duchenne Muscular Dystrophy (DMD).

Though DNA testing gives precise diagnosis, molecular heterogeneity of disease makes testing an elaborate effort in Duchenne Muscular Dystrophy (DMD) in spite of the fact that 60°% of the cases are caused by deletions. The molecular diagnosis of carriers is elaborate needing quantitation of amplifed exonic products. Use of polymorphic markers for other mutations are also involved. We had reported in a large pedigree of DMD with one exonic deletion, the status of calpain by ELISA, CPK and deletion assessed by quantitative PCR (QPCR) in mothers and female siblings. The results pointed to the fact that calpain test is positive in true carriers (showing gene deletion). Status of catpain was assessed in many unrelated female members of DMD families carrying other exonic deletions, which was positive to calpain changes in true carriers.

Carrier Detection and Prenatal Diagnosis of Hemophilia A in a Korean Population by Analysis of Two Variable Dinucleotide Tandem Repeats within the Factor VIII Gene / 대한산부인과학회잡지

We have undertaken this study to identify the usefulness of two variable dinucleotide tandem repeats within the factor VIII gene for carrier detection and prenatal diagnosis of hemophilia A in the Korean population. We have analyzed these polymorphisms in 50 unrelated Korean mothers of patients with severe hemophilia A, using polymerase chain reaction. The expected heterozygosity rates of the intron 13 and intron 22 dinucleotide repeats were 56% and 40%, respectively. Analysis of the intron 13 and intron 22 dinucleotide repeats revealed heterozygous patterns in 29(58%) and 17(34%) of 50 mothers studied, respectively. The combined overall informativity of the intron 13 and intron 22 dinucleotide repeats was 68%. Using linkage analysis with the intron 13 dinucleotide repeats, we have attempted three cases of carrier detection and two cases of prenatal diagnosis in two families of patients with severe hemophilia A. Two pregnant women were diagnosed as carriers, and the other patients as non-carrier Prenatal diagnosis revealed an unaffected male in one fetus, and an unaffected female in another fetus. This data demonstrated that the analysis of the intron 13 and intron 22 dinucleotide repeats very useful in the carrier detection and prenatal diagnosis of hemophilia A in the Korean population.

Usefulness of HhaI and MseI DNA Polymorphism of Factor IX Gene in the Molecular Genetic Diagnosis of Hemophilia B in Korean Population / 대한산부인과학회잡지

OBJECTIVES: Hemophilia B has been known to result from more than 500 kinds of mutations. And it is difficult to find out a mutation specific for each family. Therefore, linkage analysis of DNA polymorphism within or near the factor IX gene has been frequently used in the clinical practice for molecular genetic diagnosis of hemophilia B. But the ethnic variation makes more difficult to apply useful markers in Caucasian population. To investigate the usefulness of the MseI and HhaI polymorphism in Korean population, we analysed the MseI and HhaI polymorphism. METHODS: Forty-five normal Korean and thirteen parents of the hemophilia B patients, using PCR and restriction enzyme analysis. RESULTS: The heterozygosity rate of MseI polymorphism was 49.7% and that of HhaI polymorphism was 25.5%. CONCLUSION: These data indicated that PCR-based analysis of MseI and HhaI polymorphism of factor IX was useful in molecular genetic diagnosis of hemophilia B in Korean population.

Carrier Dectection and Prenatal Diagnosis of Hemophilia Ain Korean Populations Using PCR Analysis of DNA Polymorphismin St14 VNTR Locus / 대한산부인과학회잡지

At present, because of enormous variety of mutations in hemophilia A, carrier detection and prenatal diagnosis by DNA analysis has been relied almost always on indirect detection using linkage analysis of DNA polymorphisms withim or near to the factor VIII gene. However, there is marked ethnic variation in the incidence of heterozygosity for a given DNA polymorphism. So it is very important to find out which DNA polymorphism pattern is useful in Korean families with hemophilia A for carrier detection and prenatal diagnosis. To identify the usefulness of DNA polymorphism in St14 VNTR locus for carrier detection and prenatal diagnosis of hemophilia A in Korean populations, we have analysed the DNA polymorphism in St14 VNTR locus in 80 Korean families with hemophilia A using polymerase chain reaction. We could identify 14 alleles in subjects studied, which ranges from 620 bp to 2830 bp. Expected heterozygosity rate, calculated from the allele frequencies, was 78.7%, and observed heterozygosity rate was 71.3% (57/80). Carrier detection was performed in 43 women from families informative with St14 VNTR : Seventeen women were diagnosed as non-carriers, 11 women as carriers. And 15 women were suspected to be carriers since they were from families of sporadic cases of hemophilia A. And prenatal diagnosis was done in 4 pregnant carrier women : noe fetus proved to be normal males, two fetuses to be normal females, and one to be a carrier. And five pregnant women, suspected to be carrier since they were from families of sporadic cases of hemophilia A, underwent prenatal diagnosis : One fetus was diagnosed as a normal mali, one as a normal female, two as possible carriers, and one as a possible affeted mali, whom the analysis of factor VIII level in fetal blood by cordocentesis revealed to be affected by hemophilia A. These data indicate that PCR-based analysis of St14 VNTR is very useful for the carrier detection and prenatal diagnosis of hemophilia A in Korea.

The prevalence study on restriction fragment length polymorphism analysis for the detection of hemophilia A carrier

We have analyzed two (BclI and XbaI) intragenic restriction fragment length polymorphisms (RFLPs) and St14 (DXS52) variable number of tandem repeats (VNTR) by rapid PCR method in 97 unrelated normal subjects. The incidences for positive Bc1I and XbaI polymorphic sites in the Koreans were 81% and 72%, respectively, which were higher than other ethnic groups but similar to that reported in the Chinese or Japanese, giving the heterozygosity rate of 0.32 and 0.40, respectively. The amplified allele size was 880 bp with no other polymorphism in the analysis of St14 (DXS52) VNTR. This finding should be taken into account in the planning of a prenatal diagnosis program for ethnic Koreans

Carrier detection and prenatal diagnosis of haemophilia / 中国输血杂志

Objects To establish a simple,rapid carrier detection and prenatal diagnosis system for hemophilia.Methods Thirty-eight HA families were tested for the intron 22 and 1 inversions in factor VIII gene by LD-PCR and PCR.The remaining inversion negative families,but with family history,were screened using linkage analysis with 8 combined polymorphic markers,including St14,F8IVS13,CA22,DXS15,DXS9901,G6PD,DXS1073,and DXS1108.For sporadic families,the whole gene sequencing was applied directly to detect the mutation.For HB families,linkage analysis with 6 STRs,including DXS1192,DXS1211,DXS8094,DXS8013,DXS1227 and DXS102,was applied to get quick diagnostic information.The whole gene sequencing was used to get the final diagnosis.The rapid fluorescent PCR combined with polymorphism markers were applied for linkage analysis in HA and HB families,respectively.As soon as the pregnancy was identified,additional Amelo site detection would be performed.Results In 38 HA families,introns 22 and 1 inversions were found in 10 and 1 probands,respectively.The diagnostic rates of St14,F8IVS13,CA22,DXS15,DXS9901,G6PD,DXS1073 and DXS1108 were 61.11%,76.67%,71.43%,70.59%,62.50%,10.00%,75.00% and 50.00%,respectively.Combining inversion detection and linkage analysis,the diagnostic rate of carrier detection and prenatal diagnosis of families with HA family history were both 100%.One intron 22 inversion and 3 mutations were detected in 4 sporadic families.The total diagnostic rate of 38 HA families was 94.81%.And 10 mutations were detected in the 12 HB families.Combined with the linkage analysis,the total diagnostic rate was 96.88%.Conclusions Introns 22 and 1 inversion screening combined with the linkage analysis,using the highly informative polymorphic markers,can be used for carrier detection and prenatal diagnosis in Chinese HA families.The direct sequencing of FⅨ with the linkage analysis can be successfully applied for carrier detection and prenatal diagnosis of HB families.