Number needed to treat and reduction of outcomes with RAAS inhibitors

Abstract

Incorporating the results of randomized trials into clinical practice is of high priority for physicians. In this regard, number needed to treat (NNT) has given decision makers access to a more intuitive statistical tool compared with relative risk reduction (RRR) in assessing treatment efficacy. Objective: Mortality and cardiovascular (CV) events were compared in hypertension trials involving angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARB) based on NNTs to illustrate differences in CV protection of these two classes. Design and objectives: All-cause and CV mortality as well as coronary and cerebrovascular events were analysed in a selection of 20 large randomized trials enrolling a total of 158 998 hypertensive patients as previously reported in a meta-analysis published by van Vark et al. in the European Heart Journal in 2012. NNT was calculated over the 4.3 years follow-up as the inverse of the absolute risk reduction between active treatment and comparator. Results: Among renin-angiotensin-system antagonists, only ACE inhibitors significantly reduced all-cause mortality. Respectively 70 and 124 patients have to be treated with an ACE-inhibitor to prevent one all-cause and cardiovascular death. For ARBs, with the same objectives, respectively 446 and 750 patients have to be treated. The protective effect of ACE inhibitors is due more to coronary event reduction (NNT=54) than to cerebrovascular events reduction (NNT=1415). For ARBs the trend was opposite, showing a greater decrease in cerebrovascular events (NNT=173) than in coronary events (NNT=3580). Among ACE inhibitor trials, the largest mortality reductions were observed in ASCOT-BPLA, ADVANCE, and HYVET which studied perindopril (RRR 13%, P<0.001), due to reduction in both coronary event reduction (NNT=109) and cerebrovascular events (NNT=131). Conclusion: In hypertension trials, NNT analysis of morbidity and mortality provides relevant figures to compare the cardioprotective effect of treatments. This analysis confirms that coronary event reduction is an important component of mortality reduction observed with ACE inhibitors.