5 Transformation of Evidence
Key Recommendation: Clinical trials should be analysed using data from the intention-to-treat (ITT) population. All statistically significant clinical events should be included in base-case analyses. For clinical events with a p value close to 0.05, consideration should be given to the magnitude of effect; whether the results are likely to be clinically significant; the relevance and validity of composite measures; and whether statistical significance has been demonstrated in an independent study. The exclusion of any event from an analysis should be justified.
It is important to make sure the outcomes most relevant to the condition are included in the CUA and that they reflect the perspective and scope of the model. This will often require incorporating information on relative treatment effects (usually obtained from clinical trials) with baseline health events.
Outcomes included in the model may include (but are not limited to):
- probability of success or failure
- adverse events
- discontinuation/loss to follow-up
These outcomes should be well defined, mutually exclusive, and generally long-term or final outcomes.
5.1.1 Use of Surrogate versus Clinically Important Outcome Measures
Economic analysis should ideally be based on studies that report clinically important outcome measures. These are valid outcomes that are important to the health of the patient.
In some cases, only surrogate outcomes may be available. These are a substitute for a clinically meaningful endpoint, and measure how a patient feels, functions or survives.
Surrogate measures should only be used in CUAs where no alternative health outcome data are available. Caution must be used when using surrogate measures, as these may not necessarily translate into clinically relevant and effective outcomes.
5.1.2 Analysing Data from Clinical Trials
Clinical trials should be analysed using data from the intention-to-treat (ITT) population, rather than per protocol (PP), in order to take into account outcomes of all patients irrespective of whether they received treatment. For further information on data sources to be used when estimating relative treatment effects, refer to Chapter 4.
Where ITT analysis has not been reported, the effectiveness rates should ideally be recalculated by adding to the ‘on treatment’ participant population for th