Translation and cross-cultural adaptation of the Italian version of the Pain-Invalidation Scale (IT-P-IS) in patients with fibromyalgia

Autori

Bisconti Mattia (Department of Human Neurosciences, Sapienza University of Rome, Rome, Italy)

Caterina Caroli (Department of Human Neurosciences, Sapienza University of Rome, Rome, Italy)

Leonardo Pellicciari (IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy)

Domenico Angilecchia (Department of Human Neurosciences, Sapienza University of Rome, Rome, Italy)

Piercarlo Sarzi Puttini (Department of Biomedical and Clinical Sciences, University of Milan, Milan, Italy)

Giuseppina Fabio (Vice President Italian Association Fibromyalgia Syndrome, Milano)

Filippo Maselli (Department of Human Neurosciences, Sapienza University of Rome, Rome, Italy)

Giuseppe Giovannico (Department of Medicine and Health Science “Vincenzo Tiberio”, University of Molise, Campobasso, Italy)

Massimo Esposto (Department of Physical and Rehabilitation Medicine, Fondazione Policlinico Universitario Campus Bio-Medico, Rome, Italy)

Background and aims

Patients with fibromyalgia (FMS) frequently report feeling dismissed or invalidated by healthcare professionals, close others, and even themselves. These experiences undermine the legitimacy of their pain, reduce self-efficacy, and may exacerbate disability. Invalidation—encompassing disbelief, stigma, and overprotection—is a specific psychosocial stressor that can be more harmful than the absence of social support. The Pain-Invalidation Scale (P-IS) assesses the invalidation and includes 24 items across four domains: self-invalidation, invalidation by immediate others, healthcare professionals, and over-attentive others. Each domain contains six items rated on a 7-point Likert scale (score range: 6–42 points). Despite its clinical relevance, the P-IS is not available in Italian. This study aimed to translate and cross-culturally adapt the Pain-Invalidation Scale (P-IS) into Italian and to test its psychometric properties.

Methods

This COSMIN compliant validation study received ethical approval from the University of Molise (Prot n. 06/2024).

The P-IS was translated into Italian using Beaton’s guidelines: forward translation, synthesis, back-translation, and expert review.

Adults (≥18 years) with medically diagnosed FMS and fluent in Italian were recruited through the Italian Associationn Fibromyalgic Syndrome national newsletter. Participants completed the Italian Pain Invalidation Scale (IT-P-IS) and other specific and generic measurement instruments. A subsample (n=30) completed the IT-P-IS again after five days to assess test-retest reliability.

The statistical plan followed the COSMIN recommendation. Structural validity was examined using confirmatory factor analysis (CFA); model fit was defined as CFI/TLI≥0.95, RMSEA≤0.06, and SRMR≤0.08. Internal consistency was assessed via Cronbach’s α; test-retest reliability via intraclass correlation coefficient (ICC); measurement error via minimal detectable change (MDC95). Construct validity was evaluated via hypothesis testing through Spearman’s correlations with other measurement instruments. Feasibility was assessed through floor/ceiling effects (>15%).

Results

Between 15 May 2024 and 30 April 2025, 164 individuals (94.5% female) completed the IT-P-IS. CFA supported a four-factor structure (CFI=0.992, TLI=0.991, RMSEA=0.047, SRMR=0.061). Internal consistency was excellent across all sections (α=0.885–0.961). Test-retest reliability in a subsample of 30 participants showed good to excellent ICC values (0.809–0.967). The MDC95 values indicated a low measurement error (11.3–5.4 points across sections). Construct validity was satisfactory, with over 75% of correlations confirming a priori hypotheses. No ceiling effects were observed; a floor effect was noted in SectionC.

Conclusion

The IT-P-IS demonstrated strong psychometric properties, including excellent internal consistency and test-retest reliability, as well as satisfactory construct validity. These results support the use of the IT-P-IS as a reliable and valid tool for assessing pain invalidation in Italian populations with fibromyalgia.

REFERENCES

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