To determine psychometric properties of the PROMIS-10 and Standard Stroke Question Set (by International Consortium for Health Outcome Measures) presented as a new 15-item Patient Related Outcome (PRO), for patients with: acquired Brain Injury (ABI), Multiple sclerosis (MS) and Parkinson's disease (PD). In an eight centre, UK wide, cross-sectional study we approached patients during their routine follow-up to complete: a disease-specific instrument (European Brain Injury Questionnaire, Multiple Sclerosis Impact Scale, and Parkinson's disease questionnaire); General Health questionnaire with a Quality of life measure (EQ-5D); and PRO. We validated the PRO using factor analysis to define the latent construct domains, then calculated the internal consistency (Cronbach's-alpha), and construct validity (correlation). There were 340 patients with ABI (N = 91, median age = 55.1, 41% female), MS (N = 99, age = 58.9, 69%) and PD (N = 150, age = 74.5, 40%). Factor analysis suggested the PRO offered three domains of: physical health; functionality-capacity and mental health. All factors correlated strongly with the three disease-specific instruments, and the overall PRO had a large correlation with the EQ-5D (correlation>0.8) offering good construct validity and excellent internal consistency (proportional to>0.89).