Development and validation of a patient-reported gout attack intensity score for use in gout clinical studies.

Abstract

Inflammation-related symptoms such as pain, swelling and tenderness of the affected joint are frequently assessed using 5-point diary rating scales in gout clinical trials. Combining these into a single gout attack symptom intensity score may be a useful summary measure for these data, which is potentially more responsive to change compared with the individual components. The objective of this study was to develop a patient-reported gout flare intensity score, the Gout Attack Intensity Score (GAIS), for use in clinical studies, that includes components for gout-related pain, swelling and tenderness. Data from a randomized controlled trial comparing anakinra to standard of care for the treatment of acute gout attacks were used for this study. A 7-day flare diary was completed by patients, including questions relating to intensity of pain, swelling and tenderness (5-point rating scales). Scalability of these items was assessed using Mokken Scale Analysis, and reliability using greatest lower bound reliability coefficients. Known-groups validity was evaluated, as well as the responsiveness to change and the presence of floor and ceiling effects. Scalability of the single items was supported, and GAIS scores were reliable (greatest lower bound >0.80). GAIS scores demonstrated responsiveness to change with high effect sizes (>0.8), and discriminated better between responders and non-responders compared with its single-item components. No floor and ceiling effects were found. The GAIS seems to be a reliable and responsive instrument for assessing patient-reported gout attack intensity that may be used in gout clinical studies.