Centre for Health Services Development, University of Wollongong, Wollongong, New South Wales, Australia.
Pharmacoeconomics. 2011 Feb;29(2):87-96. doi: 10.2165/11585910-000000000-00000.
Economic analysis and assessment of net clinical benefit often requires estimation of absolute risk difference (ARD) for binary outcomes (e.g. survival, response, disease progression) given baseline epidemiological risk in a jurisdiction of interest and trial evidence of treatment effects. Typically, the assumption is made that relative treatment effects are constant across baseline risk, in which case relative risk (RR) or odds ratios (OR) could be applied to estimate ARD. The objective of this article is to establish whether such use of RR or OR allows consistent estimates of ARD. ARD is calculated from alternative framing of effects (e.g. mortality vs survival) applying standard methods for translating evidence with RR and OR. For RR, the RR is applied to baseline risk in the jurisdiction to estimate treatment risk; for OR, the baseline risk is converted to odds, the OR applied and the resulting treatment odds converted back to risk. ARD is shown to be consistently estimated with OR but changes with framing of effects using RR wherever there is a treatment effect and epidemiological risk differs from trial risk. Additionally, in indirect comparisons, ARD is shown to be consistently estimated with OR, while calculation with RR allows inconsistency, with alternative framing of effects in the direction, let alone the extent, of ARD. OR ensures consistent calculation of ARD in translating evidence from trial settings and across trials in direct and indirect comparisons, avoiding inconsistencies from RR with alternative outcome framing and associated biases. These findings are critical for consistently translating evidence to inform economic analysis and assessment of net clinical benefit, as translation of evidence is proposed precisely where the advantages of OR over RR arise.
经济分析和评估净临床获益通常需要估计给定感兴趣司法管辖区的基线流行病学风险和试验治疗效果的二项结局（例如生存、反应、疾病进展）的绝对风险差异（ARD）。通常，假设相对治疗效果在基线风险中是恒定的，在这种情况下，可以应用相对风险（RR）或比值比（OR）来估计 ARD。本文的目的是确定 RR 或 OR 的这种使用是否允许对 ARD 进行一致的估计。ARD 是从替代效果框架（例如死亡率与生存）计算得出的，应用了使用 RR 和 OR 转换证据的标准方法。对于 RR，将 RR 应用于司法管辖区的基线风险以估计治疗风险；对于 OR，将基线风险转换为几率，应用 OR，并将治疗几率转换回风险。RR 用于替代效果框架时，ARD 的估计会发生变化，而 OR 用于替代效果框架时，ARD 的估计会发生变化，只要存在治疗效果且流行病学风险与试验风险不同，RR 就会发生变化。此外，在间接比较中，OR 用于替代效果框架时，ARD 一致估计，而 RR 计算允许不一致，ARD 的替代效果框架的方向，更不用说程度。OR 确保在将来自试验环境和直接和间接比较中的试验的证据进行翻译时一致地计算 ARD，从而避免了 RR 与替代结局框架相关的不一致性和潜在偏倚。这些发现对于一致地将证据转化为经济分析和评估净临床获益至关重要，因为正是在 RR 具有优势的情况下，才提出了对 OR 的证据进行翻译。
