Rasch Measurement and Patient Reported Value Claims: A Primer for Hemophilia.

This commentary proposes that Rasch Measurement Theory (RMT) is an innovative method for assessments of patient-centric therapy response in hemophilia A and B, as they are in other disease states or target patient populations. RMT is a necessary and sufficient approach to moving from ordinal observations to interval measurement, which has arithmetic properties. This applies across the board in hemophilia and other disease states for clinical value claims, patient centric or subjective value claims as well as those for anticipated drug utilization and other medical care resources. The purpose of this commentary is to point out limitations regarding current methods for making claims regarding hemophilia response and to propose a new start in hemophilia studies to identify core claims that meet required measurement standards. This applies to both the development of new patient reported outcome instruments as well as the evaluation of existing instruments, with a focus on polytomous instruments and their sub-domains, to evaluate their possible application as measures that approximate RMT requirements.