Background/Purpose: The use of immune checkpoint inhibitors (ICI) continues to increase with an expanding number of indications across varying cancer types and stages. ICIs can induce an inflammatory arthritis (ICI-IA) which can have significant impacts on patient function and quality of life. The Health Assessment Questionnaire Disability Index (HAQ-DI) is a health-related patient-reported outcome measure widely used to assess functional limitations in patients with rheumatoid arthritis. To date, use of the HAQ-DI has not been studied in patients with ICI-IA. Our objective was to evaluate the measurement properties (reliability, construct validity and responsiveness) of the HAQ-DI in patients with ICI-IA.

Methods: All patients enrolled in a multicenter prospective cohort, with a diagnosis of ICI-IA, who completed a baseline HAQ-DI at first study visit were included. Demographic, clinical and laboratory data including the HAQ-DI were extracted from the study database. Internal consistency reliability was assessed using Cronbach’s alpha coefficient with values ≥ 0.7 considered acceptable. Construct validity was assessed by correlating HAQ-DI scores with other measures of disease activity including c-reactive protein (CRP), tender joint count (TJC), swollen joint count (SJC), patient global assessment of disease activity (PtGA) as well as physician global assessment of disease activity (PGA). Responsiveness was assessed by calculating the standardized response mean (SRM) and effect size (ES) in those with ≥ 3-point improvement on the PGA (defined a priori) at 3-6 month follow up.

Results: Ninety-six patients from 9 centers were included in this study. The median age of study participants was 67 years (range 39-84), 50% were female and the most common malignancies were melanoma and non-small cell lung cancer (Table 1). The most common presentation of ICI-IA was polyarticular involvement (64%) with a median TJC of 6 (range 0-36) at baseline and SJC of 2 (range 0-30). The median HAQ-DI at baseline was 0.5 (range 0, 3). The median HAQ-DI at 6 months (n=66) was 0.125 (range 0, 2.375). HAQ-DI floor and ceiling effects for the whole group were 24% and 1%, respectively. Cronbach’s alpha for the 8 HAQ-DI categories ranged from 0.72-0.91 and for the 20 HAQ DI Items was 0.94 suggesting high internal consistency reliability (Table 2). The HAQ-DI had a significant positive correlation with CRP, TJC, SJC, ptGA and PGA (Table 3). Responsiveness of the HAQ-DI was moderate with an SRM =1.4 and ES = 0.3 when calculated in the 23 participants with ≥ 3-point improvement on the PGA.

Conclusion: In this prospective cohort study, the HAQ-DI was reliable, valid and sensitive to change in patients with ICI-IA. Future research will further explore content validity, establish the minimal clinically important difference of the HAQ-DI in ICI-IA and explore correlation of the HAQ-DI with the physical functioning components of other patient-reported outcome measures currently validated in cancer patients.

Table 1: Characteristics of subjects at time of baseline assessment (n=96)

Legend: TJC = tender joint count; SJC = swollen joint count, PtGA = patient global assessment of disease activity, PGA = physician global assessment of disease activity, CRP = c-reactive protein, CTCAE = common terminology criteria for adverse events, HAQ-DI = health assessment questionnaire disability index

Table 2: HAQ-DI Score component and overall internal consistency reliability (Cronbach’s alpha) component analysis at baseline (n=96)

Table 3: HAQ correlations with clinical and demographic variables

Legend: CRP = c-reactive protein, TJC = tender joint count, SJC = swollen joint count, PtGA = patient global assessment of disease activity, PGA = physician global assessment of disease activity

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/validation-of-the-health-assessment-questionnaire-disability-index-in-immune-checkpoint-inhibitor-induced-inflammatory-arthritis/