Refractory hypertension is associated with the haptoglobin 2-2 phenotype.

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.