Aims

Recent trials have evaluated sodium-glucose co-transporter 2 inhibitors in patients with heart failure (HF). We sought to assess the robustness of findings from these trials using the fragility index (FI).

Methods and results

Fragility index is defined as the minimum number of patients that must be moved from the 'non-event' to the 'event' group to turn a statistically significant result to non-significant. In addition to FI, fragility quotient [(FQ); FI divided by the sample size] was calculated to assess the proportion of events that must be moved to change the significance. For statistically non-significant outcomes, reverse fragility index (RFI) and reverse fragility quotient (RFQ) were calculated. Robustness of findings after pooling data from all three trials was also assessed. A robust reduction in first HF hospitalization or cardiovascular mortality was seen with dapagliflozin (FI = 62 and FQ = 0.013), empagliflozin (FI = 50 and FQ = 0.013), and sotagliflozin (FI = 60 and FQ = 0.049). Dapagliflozin nominally improved all-cause and cardiovascular mortality, with modest FI (n = 8 and 5) and FQ (0.002 and 0.001). Empagliflozin and sotagliflozin did not demonstrate statistically significant reductions in all-cause mortality, with modest RFI (empagliflozin: RFI = 26 and RFQ = 0.007; sotagliflozin: RFI = 6 and RFQ = 0.005). A similar trend was seen with cardiovascular mortality (empagliflozin: RFI = 24 and RFQ = 0.006; sotagliflozin: RFI = 7 and RFQ = 0.006). Upon meta-analysis, the result for first HF hospitalization or cardiovascular mortality was robust (FI = 95 and FQ = 0.010). The reductions in all-cause (FI = 12 and FQ = 0.001) and cardiovascular mortality (FI = 9 and FQ = 0.001), while statistically significant, were fragile.

Conclusion

Improvement in the composite outcome of first HF hospitalization or cardiovascular death was highly concordant and robust across sodium-glucose co-transporter 2 inhibitor trials. In contrast, secondary endpoints of all-cause and cardiovascular mortality were statistically fragile, underscoring the need to power trials for mortality to fully understand the benefit of therapies on fatal events.

Aims

This study aimed to investigate the reporting of subgroup analyses in heart failure (HF) randomized controlled trials (RCTs) and to determine the strength and credibility of subgroup claims.

Methods and results

All primary HF RCTs published in nine high-impact journals from 1 January 2008 to 31 December 2017 were included. Multivariable regression analysis was used to identify factors that may favour the reporting of results in specific subgroups. Strength of the subgroup effect claimed was classified into (i) strong, (ii) likely, or (iii) suggestive. Credibility of subgroup claim was scored using a pre-specified 10 pointer criteria. Of the 261 HF RCTs studied, 107 (41%) reported subgroup analyses. Twenty-five (23%) RCTs claimed a subgroup effect for the primary outcome of which six (24%) made a strong claim, eight (32%) claimed a likely effect, and 11 (44%) suggested a possible subgroup effect. Seven of the 25 RCTs did not employ interaction testing for subgroup claims of the primary outcome. Three out of 10 pre-specified credibility criteria were satisfied by half of the trials. Fourteen trials justified the choice of subgroups, and 10 explicitly stated they were underpowered to detect differences within subgroups. Source of funding did not influence the frequency of reporting subgroup analyses (OR 0.53, 95% CI 0.78-3.62, P = 0.52).

Conclusions

Appropriate credibility criteria were rarely met even by HF RCTs that held strong subgroup claims. Subgroup analyses should be pre-specified, be adequately powered, present interaction terms, and be replicated in independent data before being integrated into clinical decision making.

The coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has important implications for the safety of participants in clinical trials and the research staff caring for them and, consequently, for the trials themselves. Patients with heart failure may be at greater risk of infection with COVID-19 and the consequences might also be more serious, but they are also at risk of adverse outcomes if their clinical care is compromised. As physicians and clinical trialists, it is our responsibility to ensure safe and effective care is delivered to trial participants without affecting the integrity of the trial. The social contract with our patients demands no less. Many regulatory authorities from different world regions have issued guidance statements regarding the conduct of clinical trials during this COVID-19 crisis. However, international trials may benefit from expert guidance from a global panel of experts to supplement local advice and regulations, thereby enhancing the safety of participants and the integrity of the trial. Accordingly, the Heart Failure Association of the European Society of Cardiology on 21 and 22 March 2020 conducted web-based meetings with expert clinical trialists in Europe, North America, South America, Australia, and Asia. The main objectives of this Expert Position Paper are to highlight the challenges that this pandemic poses for the conduct of clinical trials in heart failure and to offer advice on how they might be overcome, with some practical examples. While this panel of experts are focused on heart failure clinical trials, these discussions and recommendations may apply to clinical trials in other therapeutic areas.