title: Refractory hypertension is associated with the haptoglobin 2-2 phenotype.
abstract: BACKGROUND
  Many cases of refractory hypertension cannot be attributed to specific identifiable factors. Haptoglobin polymorphism has been suggested as a candidate genetic marker in essential hypertension. The aim of this study was to investigate the distribution of haptoglobin types in patients with refractory hypertension.
  
  
  METHODS
  Haptoglobin polymorphism was studied in 383 patients with non-refractory and 62 patients with refractory hypertension. Haptoglobin was typed using starch gel electrophoresis of haemoglobin-supplemented serum.
  
  
  RESULTS
  In the group of patients with refractory hypertension, the relative allele frequency of haptoglobin 1 (0.266) was lower than in the group with non-refractory hypertension (0.385: P < or = 0.05). The relative frequency of haptoglobin 2-2 was 39% in the non-refractory compared with 56% in the refractory group (P < or = 0.05). In the latter group, the relative frequency of haptoglobin 2-2 was highest (75%) in patients requiring medication with four classes of drug.
  
  
  CONCLUSIONS
  Hypertension patients with the haptoglobin 2-2 phenotype are at higher risk of developing refractory hypertension than those with other haptoglobin phenotypes.
authors.affiliation: Department of Clinical Chemistry, University Hospital, Gent, Belgium.
authors.forename: J R
authors.initials: JR
authors.lastname: Delanghe
authors.forename: D A
authors.initials: DA
authors.lastname: Duprez
authors.forename: M L
authors.initials: ML
authors.lastname: De Buyzere
authors.forename: B M
authors.initials: BM
authors.lastname: Bergez
authors.forename: L R
authors.initials: LR
authors.lastname: Claeys
authors.forename: G G
authors.initials: GG
authors.lastname: Leroux-Roels
authors.forename: D L
authors.initials: DL
authors.lastname: Clement
mesh_terms: D000483:Alleles; D000959:Antihypertensive Agents / Q000008:administration & dosage / Q000627:therapeutic use; D001794:Blood Pressure; D004338:Drug Combinations; D005260:Female; D005787:Gene Frequency; D005819:Genetic Markers; D006242:Haptoglobins / Q000235:genetics*; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D017379:Hypertrophy, Left Ventricular / Q000209:etiology; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D011110:Polymorphism, Genetic / Q000235:genetics
chemical_list: D000959:Antihypertensive Agents; D004338:Drug Combinations; D005819:Genetic Markers; D006242:Haptoglobins