Intention to treat

Intention-to-treat (ITT) analysis refers to analysis based on the initial treatment assignment, not on the treatment eventually received. This type of analysis, now widely accepted as the standard for analysing clinical trials, provides an unbiased comparison across the treatment groups. If cross-overs or drop-outs from the clinical trial are not random and imbalanced across treatment groups (i.e. potentially related to characteristics of the new intervention), then comparisons of groups as treated (‘On Therapy’- OT) may suffer from bias. When using the efficacy results from trials in economic models, care needs to be taken to select the most appropriate efficacy values (ITT or OT) from the source studies, especially if movements between treatment groups of cohort members are being considered explicitly in the model. A validation check is useful to see how well the model replicates the results of the source study.