P. Strazzullo et al., Prediction and consistency of blood pressure salt-sensitivity as assessed by a rapid volume expansion and contraction protocol, J NEPHROL, 13(1), 2000, pp. 46-53
Background: This multicenter trial in essential hypertensive patients (n=94
) is aimed i) to evaluate the distribution of blood pressure salt-sensitivi
ty by a rapid volume expansion/contraction protocol over three days; ii) to
investigate the within-patient reproducibility and to identify predictors
of the response to the test; iii) to compare this response with the respons
e to dietary NaCl restriction.
Methods: The study design included: 1) screening for salt-sensitivity by th
e rapid test; 2) a controlled trial of dietary salt restriction; 3) repetit
ion of the rapid test in a subgroup of patients.
Results: The mean BP response to the rapid test fitted a Gaussian curve. In
multivariate regression analysis, controlling for the effect of potential
confounders, the blood pressure increment during the intravenous saline inf
usion was the best independent predictor of the response to the test (r=0.7
13) with minor contributions by the 24-h urinary sodium excretion before th
e test and by baseline fasting serum insulin. These three variables togethe
r explained 61% of the overall variability of the response. The Spearman ra
nk correlation coefficient between the BP response to the rapid test and th
e response to the dietary protocol was 0.21, p=0 05. Upon repetition of the
rapid test, the correlation coefficient between the responses observed on
the two occasions was 0.60 (n=19, p<0.01); there were no patients misclassi
fied across the extreme tertiles of the distribution of salt-sensitivity.
Conclusion: We conclude that the rapid test reproducibly identified patient
s in the upper and lower parts of the distribution of salt sensitivity. The
analysis of possible predictors of the response to the test suggested that
the evaluation of the blood pressure response to saline infusion, upon car
eful standardization of dietary NaCl intake, may represent an. alternative
to the completion of the whole test for the screening of the salt-sensitivi
ty.