Concerns with Patient Reported Outcome Measurement and Value Claims for Therapy Response: The Case of Mavacamten and Symptomatic Hypertrophic Cardiomyopathy (SHCM)

Fundamental measurement is the basis for a rational assessment of patient reported outcome (PRO) value claims; both as response to therapy and the submission of credible and evaluable value claims to formulary committees and other health system decision makers. It is important to emphasize the importance of creating interval and ratio scales as opposed to nominal and ordinal scales to support value claims; a recognition that follows from acceptance of conjoint simultaneous measurement and the contribution of Rasch or modern measurement theory (RMT). Failure to appreciate the role of RMT has led thousands of researchers simply to apply numerals to events, inappropriately applying the techniques of classical statistical analysis, with the result that all that is produced are ordinal PRO scores. Instead, we should be aiming for interval and ratio scores based on a comprehensible latent trait and the application of the Rasch model. The purpose of this brief commentary is to review the measurement properties of PRO value claims for mavacamten (Camzyos; Bristol Myers Squibb) in symptomatic hypertrophic cardiomyopathy (SHCM) and to judge whether they have any validity when judged against the requirements of modern measurement theory. The assessment includes both the recent evidence report by the Institute for Clinical and Economic Review (ICER) for mavacamten as well as pivotal randomized trial (RCT) value claims that combine clinical endpoints with PROs that fail the standards of fundamental evidence. These include the Kansas City Cardiomyopathy Questionnaire (KCCQ), the New York Heart Association (NYHA) functional classification and the EuroQuol EQ-5D-5L multiattribute health related quality of life (HRQoL) preference instrument. The review concludes that apart from purely clinical claims based on the various pivotal trials, there are no PRO claims for mavacamten in SHCM that meet the required measurement standards.