Table. Measures to Summarize Treatment Effect Using Examples of the Placement of Aortic Transcatheter Valves (PARTNER) Trials*.
| Effect Measure | PARTNER A (TAVR vs. SAVR) Estimate (95% CI) |
PARTNER B (TAVR vs. MT) Estimate (95% CI) |
Caveats |
|---|---|---|---|
| Hazard ratio | 1.01 (0.84 to 1.23) |
0.50 (0.39 to 0.65) |
• The hazard is non-intuitive to interpret. • Treatment effect is assumed constant over time; if this is not the case, the interpretation is unclear. • Presenting hazard ratio without absolute event rates can be misleading. • The statistical power depends on the number of events during the follow-up time. |
| Median survival time difference | 4.3 months (−3.9 to 12.5) |
19.3 months (9.4 to 29.2) |
• The median survival time is intuitive to interpret. • The median survival time is insensitive to early deaths or long-term survivors. • The estimation procedure is less efficient (i.e., wide 95% Cis). It may be inconsistent with hazard ratio estimates. • When the event rate is low, the median survival time is not observed. |
| Risk difference at time t (5 years) | −5.0 % (−12.6 to 2.6) |
−22.9 % (−31.1 to −14.6) |
• Risk difference is intuitive to interpret. • Risk difference does not reflect the cumulative incidence profiles before time t. |
| NNT at time t (5 years) | 20.0 (not calculated) |
4.4 (3.2 to 6.8) |
• NNT does not reflect the cumulative incidence profiles before time t. • It may be intuitive to clinicians, but may not improve patients’ understanding. • When the risk difference is not statistically significant, interpretation of NNT is unclear. |
| RMST difference at time t (5 years) | 1.0 month (−2.7 to 4.6) |
12.6 months (8.2 to 17.1) |
• RMST is intuitively interpreted as the average survival time from baseline to time t. • Clinically important time frame to evaluate RMST should be chosen a priori. • In case of low event rate, the CI of RMST can be narrow and provide sufficient evidence for a non-inferiority claim. |
CI, confidence interval; MT, medical treatment; NNT, number needed to treat; RMST, restricted mean survival time; SAVR, surgical aortic valve replacement; TAVR, transcatheter aortic valve replacement.
*
Individual patient data were not available to the authors; we reconstructed time-to-event data from the Kaplan-Meier curves in the published papers1,2 using a well-established algorithm.7 The hazard ratios (95% confidence intervals) estimated from the reconstructed data were close to the published hazard ratios and 95% confidence intervals.