Methodological considerations in the evaluation of the duration of action of antihypertensive therapy using ambulatory blood pressure monitoring.

We review the potential limitations of the two current methodologies for evaluating the duration of action of antihypertensive therapy: the smoothness index (SI) and the trough : peak ratio (TP). We propose a simple correction factor for the SI. The correction factor prevents the SI from reaching erroneous high values in situations in which the reduction in blood pressure (BP) is inadequate but very homogeneous. We refer to the corrected index as the SIn (normalized SI).