Interchangeability Observed Between 2 Measures of Minimal Disease Activity in Psoriatic Arthritis

The Health Assessment Questionnaire-Disability Index (HAQ-DI) and Patient-Reported Outcomes Measurement Information System-Physical Function (PROMIS-PF) are interchangeable in assessing minimal disease activity (MDA) in psoriatic arthritis (PsA), according to study results published in Arthritis Care and Research.

While HAQ-DI has been used for many years to assess physical function in patients with PsA, PROMIS-PF is a more current instrument that has the potential to replace HAQ-DI in the classification of MDA.

In this study, researchers collected data from 100 patients to assess the interchangeability between the 2 methods. Data included a total of 352 patient observations with up to 5 visits per patient. Mean age of participants was 52 years; 60% were women; 92% were White. Overall, 93% of participants had at least 2 consecutive visits, 84% had at least 3, 71% had at least 4, and 4% had 5 visits.

The HAQ-DI scores ranging from 0 (“no difficulty)” to 3 (“unable to do”) were collected for various patient activities, as well as for self-reported PROMIS-PF4a and PROMIS-PF computer adaptive test (CAT) measures. Researchers established crosswalk tables between the HAQ-DI and corresponding PROMIS-PF data. Kappa statistic was used to calculate agreement between the 2 definitions, where ≤0.2 corresponded to slight agreement; 0.2 to ≤0.4 was fair; 0.4 to ≤0.6 was moderate; 0.6 to ≤0.8 was substantial; and >0.8 was excellent agreement.

Kappa statistic analysis revealed that HAQ-DI and PROMIS-PF MDA definitions consistently showed excellent agreement (kappa, >0.8) at each visit, with a range of 0.83 to 0.93 for PROMIS-PF4a and 0.91 to 0.98 for PROMIS-PF CAT. Kappa values for very low disease activity were consistent with MDA measures, with a range of 0.81 to 0.88 for PROMIS-PF4a and 0.76 to 0.91 for PROMIS-PF CAT.

Overall, agreement was greater between HAQ-DI and PROMIS-PF CAT than PROMIS-PF4a, with excellent agreement in gender groups (kappa=0.93 for women; kappa=0.95 for men). In general, agreement was higher among patients aged younger than 51 years and among those with lower pain.

These results showed excellent agreement between HAQ-DI and PROMIS-PF measures, which was maintained across patient subgroups. Both measures were found to be interchangeable for calculating PsA disease activity at a threshold of ≤0.5 for HAQ-DI and ≥41.3 for PROMIS-PF.

Study limitations included the relative homogeneity of the cohort (a majority of patients were White and received disease-modifying antirheumatic drugs), which limited the applicability of results to more generalized patient groups, and the utilization of crosswalk tables, which can only be used when all values are present.

Researchers concluded, “Our study findings may encourage clinicians who administer HAQ-DI based measures to switch to PROMIS-PF.”

Reference

Chew E, Perin J, Grader-Beck T, Orbai AM. Measurement of minimal disease activity in psoriatic arthritis using PROMIS‐Physical Function or the Health Assessment Questionnaire‐Disability Index. Published online August 29, 2020. Arthritis Care Res. doi:10.1002/acr.24433