The Psychological Inflexibility in Pain Scale (PIPS): Validity and Reliability of the Japanese Version for Chronic Low Back Pain and Knee Pain

Yasuhiro Nagasawa,1,2 Ai Shibata,3 Hanako Fukamachi,4,5 Kaori Ishii,5 Rikard K Wicksell,6 Koichiro Oka5 1Department of Rehabilitation, Hasegawa Hospital, Yachimata, Chiba, Japan; 2Graduate School of Sport Sciences, Waseda University, Tokorozawa, Saitama, Japan; 3Faculty of Health and Sports Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan; 4Sport Sciences Laboratory, Japan Sport Association, Tokyo, Japan; 5Faculty of Sport Sciences, Waseda University, Saitama, Japan; 6Department of Clinical Neuroscience, Karolinska Institute, Stockholm, SwedenCorrespondence: Yasuhiro NagasawaDepartment of Rehabilitation, Hasegawa Hospital, 85 Yachimatani, Yachimata, Chiba, 289-1103, JapanTel +81 3 444 0137Fax +81 3 444 0807Email nagasawaid@toki.waseda.jpPurpose: The aim of this study was to translate the Psychological Inflexibility in Pain Scale Japanese version (PIPS-J) and inspect its validity and reliability in older patients with chronic low back pain and knee pain.Materials and Methods: The PIPS was translated into Japanese by a bilingual linguistic expert and three researchers and administered to 120 outpatients with low back pain and knee pain (61.7% women, age 73.8± 7.8 years). Construct validity and criterion validity were evaluated using confirmatory factor analysis and the correlations with the Acceptance and Action Questionnaire-II Japanese version (AAQ-II-J) and the Cognitive Fusion Questionnaire Japanese version (CFQ-J), respectively. Internal consistency using Cronbach’s alpha and test–retest reliability (n=43) were also examined.Results: Of all, 78.3% had low back pain, 55.6% had knee pain, and 44.2% both. The confirmatory factor analysis reproduced the original PIPS structure with two factors and indicated good model fit (GFI = 0.915, CFI = 0.970, RMSEA = 0.060). All items’ standardized regression weights ranged from 0.35 to 0.80. Criterion validity was shown by correlations of r = 0.58 for PIPS-J pain avoidance with the AAQ-II-J, and r = 0.45 between PIPS-J cognitive fusion and the CFQ-J. Cronbach’s alpha for the PIPS-J total score was α=0.85 (pain avoidance: 0.87; cognitive fusion: 0.68). The test–retest correlation for all 12 items was r = 0.54 (pain avoidance: 0.48; cognitive fusion: 0.54).Conclusion: Although a less relevant item was found on each of subscales, the PIPS-J appear to be fairly valid and reliable to evaluate psychological inflexibility in chronic pain among Japanese older adults.Keywords: pain avoidance, cognitive fusion, older patients, chronic low back pain, chronic knee pain