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Refractory hypertension is associated with the haptoglobin 2-2 phenotype
J R Delanghe1, D A Duprez, M L De Buyzere
1Department of Clinical Chemistry, University Hospital, Gent, Belgium.
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.
Conclusion:
Hypertension patients with the haptoglobin 2-2 phenotype are at higher risk of developing refractory hypertension than those with other haptoglobin phenotypes.