title: Impact of sickle cell trait on the thrombotic risk associated with non-O blood groups in northern Nigeria.
abstract: BACKGROUND
  The non-O blood group is an established risk factor for deep vein thrombosis (DVT), while controversy surrounds the role of sickle cell trait (SCT) as a risk factor for DVT. We hypothesised that if SCT is a risk factor for DVT, individuals with non-O blood groups and SCT (Hb AS) would have a higher risk of DVT than their counterparts with non-O blood groups and normal haemoglobin phenotype (Hb AA).
  
  
  METHODS
  We retrospectively analysed the prevalence of SCT and non-O blood groups among 148 DVT patients with control subjects in order to determine the role of SCT as a risk factor for DVT and its impact on the risk of DVT among patients with non-O blood groups.
  
  
  RESULTS
  In comparison with control subjects, DVT patients had significantly higher prevalences of SCT (35.1% vs 27.7%, p=0.04) and non-O blood groups (68.9% vs 45.9%, p=0.02). The odds ratios for DVT due to SCT, non-O blood groups with normal Hb phenotype (Hb AA) and non-O blood groups with SCT (Hb AS) were 1.3, 2.4 and 3.5, respectively.
  
  
  CONCLUSIONS
  These results suggest that SCT by itself is a weak risk factor for DVT but it has the potential of escalating the DVT risk among patients with non-O blood groups. The combined effects of elevated clotting factors (non-O group effect) and increased clotting factor activation (SCT effect) were responsible for the escalated DVT risk among patients with co-inheritance of non-O blood groups and SCT. Co-inheritance of SCT and non-O blood group is, therefore, an important mixed risk factor for DVT. This should be taken into account when assessing DVT risk profiles of patients in Africa and other parts of the world where the SCT is prevalent.
authors.affiliation: Department of Haematology, Aminu Kano Teaching Hospital, Kano, Nigeria.
authors.forename: Sagir G
authors.initials: SG
authors.lastname: Ahmed
authors.affiliation: Department of Haematology, University of Maiduguri Teaching Hospital, Maiduguri, Nigeria.
authors.forename: Modu B
authors.initials: MB
authors.lastname: Kagu
authors.affiliation: Department of Paediatrics, Aminu Kano Teaching Hospital, Kano, Nigeria.
authors.forename: Umma A
authors.initials: UA
authors.lastname: Ibrahim
authors.affiliation: Department of Haematology, University of Maiduguri Teaching Hospital, Maiduguri, Nigeria.
authors.forename: Audu A
authors.initials: AA
authors.lastname: Bukar
mesh_terms: D000017:ABO Blood-Group System / Q000032:analysis / Q000235:genetics*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001779:Blood Coagulation Factors / Q000032:analysis; D016022:Case-Control Studies; D004789:Enzyme Activation; D005260:Female; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D006441:Hemoglobin A / Q000032:analysis; D006451:Hemoglobin, Sickle / Q000032:analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D009549:Nigeria / Q000453:epidemiology; D011247:Pregnancy; D011250:Pregnancy Complications, Hematologic / Q000097:blood / Q000453:epidemiology / Q000235:genetics; D015995:Prevalence; D011655:Pulmonary Embolism / Q000453:epidemiology* / Q000209:etiology / Q000235:genetics; D012189:Retrospective Studies; D012306:Risk; D012307:Risk Factors; D012805:Sickle Cell Trait / Q000097:blood / Q000150:complications / Q000235:genetics*; D062606:Tertiary Care Centers / Q000706:statistics & numerical data; D019851:Thrombophilia / Q000453:epidemiology / Q000209:etiology / Q000235:genetics*; D020246:Venous Thrombosis / Q000453:epidemiology* / Q000209:etiology / Q000235:genetics
chemical_list: D000017:ABO Blood-Group System; D001779:Blood Coagulation Factors; D006451:Hemoglobin, Sickle; C028671:hemoglobin AS; D006441:Hemoglobin A