Validation of a Spanish version of the psychological inflexibility in pain scale (PIPS) and an evaluation of its relation with acceptance of pain and mindfulness in sample of persons with fibromyalgia

BACKGROUND: Psychological flexibility has been suggested as a fundamental process in health. The Psychological Inflexibility in Pain Scale (PIPS) is one of the scales employed for assessing psychological inflexibility in pain patients. The aim of this study was to validate the Spanish version of the PIPS and secondly, to compare it to two other psychological constructs, the acceptance of pain and mindfulness scales. METHODS: The PIPS was translated into Spanish by two bilingual linguistic experts, and then, back-translated into English to assess for equivalence. The final Spanish version was administered along with the Pain Visual Analogue Scale, Fibromyalgia Impact Questionnaire, Hospital Anxiety Depression Scale, Pain Catastrophizing Scale, Chronic Pain Acceptance Questionnaire and the Mindful Attention Awareness Scale, to 250 Spanish patients with fibromyalgia. Face validity, construct validity, reliability (internal consistency and test-retest) and convergent validity were tested. Also a multiple regression analysis was carried out.The usual guidelines have been followed for cross-cultural adaptations. RESULTS: Data were very similar to the ones obtained in the original PIPS version. The construct validity confirmed the original two-components solution which explained 61.6% of the variance. The Spanish PIPS had good test-retest reliability (intraclass correlation coefficient 0.97) and internal consistency reliability (Cronbach’s alpha: 0.90). The Spanish PIPS’ score correlated significantly with worse global functioning (r = 0.55), anxiety (r = 0.54), depression (r = 0.66), pain catastrophizing (r = 0.62), pain acceptance (r = −0.72) and mindfulness (r = −0.47), as well as correlating modestly with pain intensity (r = 0.12). The multiple regression analyses showed that psychological inflexibility, acceptance and mindfulness are not overlapped. CONCLUSIONS: The Spanish PIPS scale appears to be a valid and reliable instrument for the evaluation of psychological inflexibility among a sample of fibromyalgia patients. These results ensure the use of this scale in research as well as in clinical practice. Psychological inflexibility measures processes different from other related components such as acceptance and mindfulness.