Background/Purpose: In the assessment of chronic pain patients it is important to measure physical functioning. The National Institutes of Health’s Patient-Reported Outcomes Measurement Information System (PROMIS) initiative developed an item bank for measuring physical functioning. This PROMIS physical functioning item bank was translated into Dutch-Flemish language according to the FACIT methodology. The aim of current study was to validate the Dutch-Flemish translation of the PROMIS physical functioning item bank (DF-PROMIS-PF) in patients with chronic pain.

Methods: A paper-and-pencil or web-based survey including the full DF-PROMIS-PF (121 items), was completed by 857 chronic pain patients (77% female, mean age 49y) satisfying the ACR classification criteria of chronic pain and referred to an outpatient secondary care center for rheumatology and rehabilitation in the Netherlands. One-dimensionality was evaluated by one-factor confirmatory factor analysis. With the future strategy to develop computer adaptive tests (CAT), item response theory (IRT) models were used to evaluate the item characteristics of the two item banks. A graded item response model (GRM) was fitted and Differential Item Functioning (DIF) was evaluated for e.g. language (Dutch vs. English), by ordinal regression models. Furthermore, construct validity was studied.

Results: Through computer technical limitation, the item bank was separated during statistical analysis into DF-PROMIS-PF_A (50 PFA-items) and DF-PROMIS-PF_BC (45 PF_B– and 26 PF_C-items). These interim analysis showed that the DF-PROMIS-PF_A and DF-PROMIS-PF_BC demonstrated good fit to a one-dimensional model (both CFI=0.976 and TLI=0.975). The first factor accounted for 57% of the questionnaire variance. The results showed acceptable test information (SE<0.3) for theta between -2.3 and 3.8 for DF-PROMIS-PF_A and between -1.6 and 4 for DF-PROMIS-PF_BC. The items demonstrated no DIF with respect to survey version. DIF was present with respect to gender (2 items), age (4 items) and language (11 items). However, the impact of DIF on the total item scores was minimal. The analyses of the full DF-PROMIS-PF are in progress and will be presented at the ACR conference.

Conclusion: The first results indicate that the DF-PROMIS-PF fits a GRM and demonstrates good coverage across the range of the physical functioning domain. Nearly all Dutch item parameters match the American item parameters and likely Dutch-specific item calibrations are not needed. The DF-PROMIS-PF can be used to develop a CAT.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/validation-of-the-dutch-flemish-promis-physical-functioning-item-bank-in-patients-with-chronic-pain/