AIM: To discuss the calculation method of T/P ratio and compare it with
smoothness index(SI), in order to know which is more
stable for assessing the homogeneity of 24 h BP reduction by antihypertensive treatment. METHOD: While was studied in 60 patients with mild to moderate hypertension the efficacy of lercanidipine, each patient took part in 24 h ABPM at the end of run in period, the 6 wk and the 8 wk of treatment, respectively. Peak/trough changes, T/P ratio and
smoothness index were calculated by different methods, and their
reproducibility was compared. RESULTS: The best compromise between correct estimate of peak change and the reproducibility was the average of the adjacent 2 h with maximal BP fall, and that of trough change and reproducibility was average of the last 2 h of 24 h. Selecting all the patients to treatment, the T/P ratio showed large scatters, while selecting the responders to treatment reduced the dispersion. SI for SBP and DBP showed better reproducibility than T/P ratio at the end of 6 wk and 8 wk of treatment. CONCLUSION: When the T/P ratio is assessed, peak and trough change should preferably be computed over 2 h time window. We should select responders to treatment while calculating the T/P ratio. SI should also be recommended in the evaluation for it can be more stable for evaluating the homogeneity of 24h BP reduction than T/P ratio.