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Background: Hemophilia A is an X-linked recessively inherited bleeding disorder characterized by deficiency of procoagulant factor VIII (FVIII)., Methods: Sixty unrelated hemophilia A patients and their family members have undergone tests for carrier detection by linkage analysis using the polymorphic markers Bcl I, Xba I and Intron 13 or 22 VNTRs. In families of sporadic hemophiliacs, the carrier status of female subjects was ascertained by linkage analysis along with FVIII:C/VWD Ag estimation., Results: Of the 33 families with positive family history, the defective X chromosome was tracked in 28 mothers. The carrier status of females from hemophilia A families with positive family history, ascertained by linkage analysis and Intron 22 and 1 inversion, was made out in 85% cases. FVIII:C/VWF Ag ratio was evaluated in 36 females from 9 sporadic hemophilic families. Using the FVIII:C/VWF Ag ratio along with linkage analysis, carrier status was determined in 9 (25%) of the 36 females studied. Using Intron 22 inversion along with linkage analysis and FVIII:C/VWF Ag estimation, the informativity in female subjects from families of sporadic hemophiliacs increased from 25% to 52%., Conclusion: In the West, linkage analysis with Bcl I, Xba I and Intron 13 or 22 VNTR markers and inversion 22 offers a good tool for carrier detection of hemophilia A in India.

Intron 1 and 22 inversions were looked for in 80 severe haemophilia A patients in India using PCR and multiplex Long-Distance Subcycling-PCR, respectively. Intron 1 inversion was seen in 3 (3.75%) and intron 22 inversion was seen in 35 (43.75%) patients. Of severe haemophilics, 47.5% had either of these inversions. It is thus suggested that screening for inversions may be the first step in genetic testing of Indian haemophilics.