Reliability, validity, and simplification of the Chinese version of the Global Pain Scale in patients with rheumatoid arthritis

Abstract

Background Persistent pain is the most reported symptom in patients with rheumatoid arthritis (RA); however, effective and brief assessment tools are lacking. We validated the Chinese version of the Global Pain Scale (C-GPS) in Chinese patients with RA and proposed a short version of the C-GPS (s-C-GPS). Method The study was conducted using a face-to-face questionnaire survey with a multicenter cross-sectional design from March to December 2019. Patients aged > 18 years who met the RA diagnostic criteria were included. Based on the classical test theory (CTT) and the item response theory (IRT), we assessed the validity and reliability of the C-GPS and the adaptability of each item. An s-C-GPS was developed using IRT-based computerized adaptive testing (CAT) analytics. Results In total, 580 patients with RA (mean age, 51.04 ± 24.65 years; mean BMI, 22.36 ± 4.07 kg/m2), including 513 (88.4%) women, were included. Most participants lived in a suburb (49.3%), were employed (72.2%) and married (91.2%), reported 9–12 years of education (66.9%), and had partial medical insurance (57.8%). Approximately 88.1% smoked and 84.5% drank alcohol. Analysis of the CTT demonstrated that all items in the C-GPS were positively correlated with the total scale score, and the factor loadings of all these items were > 0.870. A significant positive relationship was found between the Visual Analog Scale (VAS) and the C-GPS. IRT analysis showed that discrimination of the C-GPS was between 2.271 and 3.312, and items 6, 8, 13, 14, and 16 provided a large amount of information. Based on the CAT and clinical practice, six items covering four dimensions were included to form the s-C-GPS, all of which had very high discrimination. The s-C-GPS positively correlated with the VAS. Conclusion The C-GPS has good reliability and validity and can be used to evaluate pain in RA patients from a Chinese cultural background. The s-C-GPS, which contains six items, has good criterion validity and may be suitable for pain assessment in busy clinical practice. Trial registration This cross-sectional study was registered in the Chinese Clinical Trial Registry (ChiCTR1800020343), granted on December 25, 2018.