Diagnosis and phenotypic assessment of Pakistani Haemophilia B carriers.

Muhammad Tariq Masood Khan,Tahir Sultan Shamsi,Abid Sohail Taj,Jawad Ahmed,Arshi Naz

doi:10.12669/pjms.333.12496

Abstract

Objectives:1: To assess the diagnostic utility of three polymorphisms (DdeI, XmnI and TaqI) and direct sequencing in haemophilia B (HB) carrier detection in Pakistani families. 2: To compare phenotypes of HB carriers with those of healthy females.Methods:The study was conducted from March 2014 till February 2016 at Khyber Medical University Peshawar and National Institute of Blood Diseases, Karachi. Individuals from HB families of Khyber Pakhtunkhwa (KP) and Federally Administered Tribal Areas (FATA) with known F9 mutation in the proband were enrolled into the study. FIX activity (FIX: C) levels were determined in all the participants. Bleeding scores (BS) and complete blood counts were performed in the female participants. Linkage analysis followed by targeted Sanger sequencing was carried out in all the study participants. Heterozygosity rate was determined for each polymorphism. Healthy females and the carrier groups were compared for bleeding phenotypes.Results:A total of 30 males and 48 females from 13 HB families were studied. The polymorphisms had a low heterozygosity rate. Direct sequencing determined the carrier status in all cases. The mean FIX: C was reduced whereas BS was raised in the carriers when compared with healthy females. A significant raise in white blood cells (WBCs) count was observed in the carriers.Conclusion:The three polymorphisms have a low heterozygosity rate in HB families from KP and FATA. Sanger sequencing is conclusive in determining carrier status in all the cases. FIX: C is low and BS is raised in the HB carriers in comparison to that of normal females. The mean WBCs count is significantly higher in the HB carriers than the normal females.

Highlights

Factor IX (FIX) is a coagulation factor with a pivotal role in the amplification and propagation phases of coagulation process.[1]
Prothrombin time (PT), activated partial thromboplastin time (APTT) and FIX: C assay were performed on STA COMPACT MAX® (STAGO, US) haemostasis analyzer
Four families were found to be heterozygous for TaqI polymorphism; five were heterozygous for XmnI polymorphism while three had DdeI polymorphism

Summary

Introduction

Factor IX (FIX) is a coagulation factor with a pivotal role in the amplification and propagation phases of coagulation process.[1] A deficiency in FIX activity (FIX:C) causes haemophilia B (HB). The FIX gene (F9) (MIM: 300746) has 8 exons and is approximately 32.7kbp long. A number of polymorphisms have been reported in this gene.[2] Of particular interest are the restriction fragment length polymorphisms (RFLPs). These restriction sites include one exonic (MnlI in exon 6), three intronic (XmnI in intron 3, TaqI and MspI in intron 4), two in the 5’ flanking region (MSeI and BamHI) and one in the 3’ untranslated region (UTR) (HhaI). Two other unique complex repeats are found in intron 1

Methods

Results

Conclusion