Researchers Identify Valid Measures of Function for Psoriatic Arthritis

The Health Assessment Questionnaire Disability Index (HAQ‐DI), the physical component score of the 12-Item Short Form Health Survey (PCS-12), and the functional capacity of the Psoriatic Arthritis Impact of Disease questionnaire (PsAID‐FC) are valid measures of function for psoriatic arthritis (PsA), according to new study findings.

To determine this, the researchers evaluated available data on HAQ‐DI, PCS-12, and PsAID‐FC from a longitudinal study conducted in 14 countries. The study included 414 consecutive adults (52% men) with definite PsA with at least 2 years of duration.

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The score distribution, construct validity, responsiveness, and thresholds of meaning of the 3 patient-reported outcome measures were evaluated.

All three outcome measures met the a priori hypotheses for construct validity. The ceiling effects were noted in 31% of patients for HAQ‐DI and 21% of patients for PsAID‐FC, although the floor effects were minimal.

After a median follow‐up of 4.1 months (interquartile range, 2.7 months) in 350 patients, 27% reported improved function, 54% reported no change in function, and 18% reported worse function, respectively.

Change scores were statistically different for groups for worsening vs no change for all 3 outcome measures. PsAID‐FC was more sensitive to change than HAQ‐DI and PCS-12.

When the researchers compared groups with worsening condition to no change, the standardized response mean square ratios were 29.9 for HAQ‐DI, 16.7 for PCS-12, and 40.1 for PsAID‐FC, respectively.

“HAQ‐DI, PCS12, and PsAID‐FC are valid measures of function for PsA,” the researchers concluded. “PsAID‐FC, a single question, performed similarly to the other [patient-reported outcome measures] and may be an additional option to measure PsA‐specific physical function.”

—Melinda Stevens

Reference:

Leung YY, Orbai A-M, de Wit M, et al; ReFlap Study Group. Comparing the patient reported physical function outcomes measures in a real-life international cohort of patients with psoriatic arthritis [published online January 21, 2020]. Arthritis Care Res (Hoboken). doi:10.1002/acr.24139.