Background & Objectives: Hemophilia A is an X-linked recessive bleeding disorder , which is caused by several different abnormalities in Factor 8 gene . Intron 22 inversion is the main causative mutation in 45-50% of severe hemophilia A patients. Moreover intron 1 inversion is responsible for >5% of severe hemophilia A cases . The goal of this study was to precisely analyse intron 1 inversion of Factor 8 gene in severe Hemophilia A patients who were negative for intron 22 inversion by Inverse Shifting-PCR (IS-PCR) method.

  Methods: In this experimental study, severe hemophilia A patients with less than 1% of normal FVIII activity level referred from Isfahan Seyedolshohada hospital were analyzed. After obtaining the consent from patients, genomic DNA from peripheral blood leukocytes was extracted. Then, Inverse-Shifting PCR method was exploited for detection of inversion of intron 1 of Factor 8 gene in patients who were negative for inversion intron 22 .

  Results : In 18 out of 32 patients who were negative for inversion intron 22, 2 (6.2%) had intron 1 inversion .

  Conclusion : The allele frequency of inversion of intron 1 at Factor 8 gene is in agreement with related studies. IS-PCR is a rapid, robust and cost effective method that can improve the molecular detection of inversion and is useful for analysis of hemophilia A patients, carrier testing and prenatal diagnosis.