Development and testing of an idiopathic pulmonary fibrosis (IPF) patient reported outcome measure (PROM)

Abstract

Patients with Idiopathic Pulmonary Fibrosis (IPF) experience debilitating symptoms which impact their health-related-quality-of-life (HQOL). Treatment options are limited but new approaches are being explored; a robust endpoint model that includes a patient reported outcome measure (PROM) to determine the impact of new treatments on patients’ symptom experience and HQOL in IPF populations is needed. The IPF-PROM study employed a mixed-methods approach, incorporating qualitative and consensus methodologies, embedding patient-centredness throughout. This enabled a robust approach to the generation of candidate items for the IPF-PROM. Twenty-nine patients (60% male, mean age 70 years) participated in focus groups at recruiting centres. IPF clinical experts (n=12) rank-ordered potential IPF-PROM domains in a Nominal Group exercise. Four hundred and twenty-five patients, nineteen caregivers and twenty-nine clinicians completed a Delphi Survey. The application of a psychometric model further reduced the items, resulting in a four domain, twelve-item IPF-PROM. Internal reliability and test-retest reliability were assessed. Eighty-five patients (82% male, mean age 75 years) completed the IPF-PROM twice, approximately three weeks apart. IPF-PROM domains (D) and overall score achieved the following intra-class correlation co-efficient: D1 0.835 (p=0.209); D2 0.895 (p=0.150); D3 0.813 (p=0.786) D4 0.863 (p=0.761); total 0.92 (p 0.784) indicating high test-retest reliability. Sixty patients completed a twelve month validation study; the IPF-PROM correlated strongly with SQRQ; mMRC; EQ-5D-5L and moderately with forced vital capacity. The validation study confirmed that the IPF-PROM is reliable and valid for use in this well characterised IPF population. Longitudinal follow-up of patients with IPF is challenging due to the morbidity and mortality associated with this condition; further studies will explore the validity and sensitivity of the IPF-PROM in different IPF populations.