Applying the Argument-Based Approach to Validation With Clinical Outcome Assessments: Strategies for Constructing a Rationale

The argument-based approach to validation, adopted in the US Food and Drug Administration's most recent Patient-Focused Drug Development draft guidance on clinical outcome assessments (COAs), emphasizes the importance of constructing explicit rationales to support proposed interpretations of COA scores. To assist researchers and sponsors in building such rationales, we describe 2 complementary strategies: (1) reviewing steps in the assessment process to identify essential assumptions and (2) evaluating potential threats to validity from construct underrepresentation and construct irrelevance. Using these strategies, we offer initial generic rationales tailored to 4 types of COAs: patient-reported outcomes (PROs), observer-reported outcomes (ObsROs), clinician-reported outcomes (ClinROs), and performance outcome (PerfO) measures. The generic rationales serve as starting points, with the expectation that they will be adapted to specific contexts of use. Greater discussion within the field is needed to advance consensus on the construction and evaluation of evidence-based rationales, with attention to the pragmatic and iterative nature of validation work.