Читать книгу Interventional Cardiology - Группа авторов - Страница 152

For a quantitative measure of patient outcome, it is common to compare the mean outcomes in each treatment group. For example, in the Catheter‐based renal denervation in patients with uncontrolled hypertension in the absence of antihypertensive medications (SPYRAL HTN‐OFF MED) study,[4] 80 patients with uncontrolled hypertension were randomized in a blinded fashion to either renal denervation or sham control with a primary efficacy endpoint of change in 24‐hour blood pressure at three months. The mean change of 24‐hour systolic blood pressure from baseline in the renal denervation and sham groups was –9.0 ± 11.0 mmHg and –1.6 ± 10.7 mmHg, respectively. The mean change between groups was –7.0 mmHg (95% CI –12.0 to 2.1; p = 0.006).

The standard deviation (SD) summarizes the extent of individual patient variation around each mean. If the data are normally distributed, then appropriately 95% of individuals will have a value within two standard deviations either side of the mean. This is sometimes called the reference range. However, for a clinical trial outcome measure it is more useful to calculate the standard error of the mean (SEM) which is SD/N. That is, precision in the estimated mean increases proportionately with the square root of the number of patients. The 95% confidence for the mean is mean ±1.96 × SEM.