Item response theory modeling and confirmatory factor analysis of the Geriatric Pain Measure (GPM-24) with a North...

The Geriatric Pain Measure (GPM-24) is a commonly used self-report pain measurement tool among older adults. To date, the GPM-24 has undergone few psychometric evaluations, with limited application of robust statistical methods such as confirmatory factor analysis (CFA). Item response theory (IRT) analysis is also needed to examine its properties at the item level. The objective of this study was to conduct a psychometric evaluation of the GPM-24 at both the factor- and item-level. In January 2024, data were collected via Qualtrics Panels from 486 older adults who completed the GPM-24. Reliability was examined using McDonald's omega coefficient, structural validity using CFA, and item properties using IRT modeling. The results showed that the overall GPM-24 and its subscales had acceptable-to-excellent reliability (ω =.77-.95). After removing two weak item cross-loadings, the five-factor model bordered on adequate fit: χ² = 4.28, CFI =.895, TLI =.881, RMSEA =.082 [CI .077-.087], SRMR =.057. Each GPM-24 item was shown to adequately discriminate between respondents with low and high levels of self-reported pain (a >1), though items 13 and 24 were identified as having the lowest discriminatory and predictive efficacy and may warrant refinement. Item 10 was most effective at distinguishing between respondents with varying levels of self-reported pain (a = 4.74). This is the first study to demonstrate that the GPM-24 is an acceptably reliable and valid tool for evaluating self-reported pain among North American older adults. Future investigations should establish cross-validation with clinical and racially diverse samples. PERSPECTIVE: This article presents the psychometric properties and item performance of the Geriatric Pain Measure (GPM-24) when tested with a North American sample of older adults. Validation of this measure can help clinicians and researchers reliably assess the impact of pain on older adults' physical functioning, affect, and quality of life.