Days alive out of hospital in heart failure: Insights from the PARADIGM-HF and CHARM trials

Background An endpoint that has received some attention in recent cardiovascular trials is ‘days alive and out of hospital’ (DAOH). Percent DAOH is a natural extension of DAOH that adjusts for differences in length of follow-up. This endpoint measure incorporates mortality and morbidity together in a way that has the potential to give more insight regarding treatment effects compared to conventional time-to-event endpoints. Other advantages of this measure include the relative ease of collection and interpretation. However, research on how to analyze this measure is still limited. Methods We propose using the one-inflated beta model to analyze percent DAOH. This model is appropriate for highly left-skewed data with a large proportion of boundary values. Data from the Prospective Comparison of ARNI [Angiotensin Receptor-Neprilysin Inhibitor] with ACEI [Angiotensin-Converting-Enzyme Inhibitor] to Determine Impact on Global Mortality and Morbidity in Heart Failure Trial (PARADIGM-HF) and Candesartan in Heart Failure Assessment of Reduction in Mortality and morbidity (CHARM) trials are used to illustrate this method. Results Statistically significant differences in percent DAOH were observed for PARADIGM-HF and CHARM in favor of treatment. In PARADIGM-HF, treatment with sacubitril plus valsartan increased DAOH on average by 11 days (95% CI: 1.4-20.9 days) and increased percent DAOH by 1.64% at a fixed follow-up length of 1,000 days (95% CI: 0.61%- 2.67%). For the CHARM overall program, the candesartan group has 1.79% more DAOH (95% CI: 0.91%- 2.68%). Conclusion DAOH, and especially percent DAOH, can enhance our understanding of treatment effects in future cardiovascular trials, and the one-inflated beta model is an appropriate choice for its analysis.