Clinical utility and applicability of smoothness index, normalized smoothness index and individualized RDH index during treatment of essential hypertension

The purpose of this study was to assess the clinical utility of the smoothness index (SI) and normalized SI (SIn), measures of duration and homogeneity of blood pressure (BP) reduction, during an observation period without antihypertensive therapy followed by a treatment period using dihydropyridines (DHP) in 54 newly diagnosed and previously untreated subjects (age 46.9 +/- 9.1 years) with essential hypertension. In addition, we aimed to describe the reduction-duration-homogeneity (RDH) index for statistical assessment of the BP reduction in the individual patient. Twenty-four-hour BP was lowered during treatment (139.2 +/- 13.9/ 91.0 +/- 7.6 mmHg vs 130.9 +/- 11.3/85.2 +/- 5.2 mmHg, p < 0.001/p = 0.001). SI showed great interindividual variation, and increased from zero to 0.9 +/- 0.8 (systolic BP) and 0.8 +/- 0.7 (diastolic BP) after treatment (p < 0.001 for both), similar results were obtained for SI(n). The RDH index revealed BP reduction in agreement with the change in individual 24-h, daytime and night-time BP. Although SI and SI(n) may add important information regarding the homogeneity of the antihypertensive effect in a group of patients, and the RDH index for the individual patient, conclusions regarding antihypertensive efficacy can be obtained from assessment of the 24-h, daytime and night-time BP changes and ambulatory BP profiles. Based on our findings, we do not recommend the use of SI or RDH index in the clinical practice.