Health care utilization and costs associated with functional status in patients with psoriatic arthritis

BACKGROUND: The Health Assessment Questionnaire Disability Index (HAQ-DI) has been validated and widely used in psoriatic arthritis (PsA) clinical trials for the assessment of patient functional status. Significant improvements in the HAQ-DI have been reported in response to therapeutic interventions; however, few US studies have evaluated the economic impact of functional disability in patients with PsA. OBJECTIVE: To evaluate the association of functional status with health care resource utilization (HCRU) and total health care costs in US patients diagnosed with PsA. METHODS: This retrospective study included adult patients with PsA enrolled in FORWARD between July 2009 and June 2019 who completed 1 or more HAQ-DI questionnaires between January 2010 and December 2019. Patient demographics, clinical characteristics, and patient-reported outcomes were collected from the most recent questionnaire. HCRU and total health care costs (2019 US dollars) for all hospitalizations, emergency department (ED) visits, outpatient visits, diagnostic tests, and procedures were assessed for the 6 months prior to survey completion. Negative binomial regression models (HCRU outcomes) and generalized linear models with γ distribution and log-link function (cost outcomes) were used to assess the relationship between HAQ-DI and HCRU and cost outcomes, respectively. RESULTS: A total of 828 patients with PsA who completed HAQ-DI questionnaires were included. The mean (SD) age was 58.5 (13.5) years, 72.3% were female, and 92.3% were White. The mean (SD) disease duration was 17.5 (12.4) years, and the mean (SD) HAQ-DI score at the time of the patients’ most recent questionnaire was 0.9 (0.7). More severe functional disability, measured by higher HAQ-DI score, was significantly associated with increased risk (incident rate ratio [95% CI]) of hospitalizations (1.68 [1.11-2.55]), ED visits (2.09 [1.47-2.96]), outpatient visits (1.14 [1.05-1.24]), and diagnostic tests (1.42 [1.16-1.74]). There was also a significant positive association between greater HAQ-DI score and increased total annualized health care costs (incremental amount [95% CI], 1.13 [1.03-1.23]) and medical costs (1.38 [1.13-1.69]), but there was no significant association found with pharmacy costs. Total adjusted average patient medical costs increased with increasing HAQ-DI score. CONCLUSIONS: Among patients with PsA enrolled in FORWARD, more functional disability—as measured by higher HAQ-DI scores—was associated with greater HCRU and increased total health care costs. These results suggest that improving functional status in patients with PsA may reduce economic burden for health care payers and systems.