• Marianne Belia Kool, Rens van de Schoot, Isabel López-Chicheri García, Ricarda Mewes, José A P Da Silva, Karoline Vangronsveld, Andreas A J Wismeijer, Mark A Lumley, Henriët van Middendorp, Johannes W J Bijlsma, Geert Crombez, Winfried Rief, and Rinie Geenen.
• Department of Clinical and Health Psychology, Utrecht University, , Utrecht, The Netherlands.
• Ann. Rheum. Dis. 2014 Mar 1; 73 (3): 551-6.

ObjectivesThe Illness Invalidation Inventory (3*I) assesses patients' perception of responses of others that are perceived as denying, lecturing, not supporting and not acknowledging the condition of the patient. It includes two factors: 'discounting' and 'lack of understanding'. In order to use the 3*I to compare and pool scores across groups and countries, the questionnaire must have measurement invariance; that is, it should measure identical concepts with the same factor structure across groups. The aim of this study was to examine measurement invariance of the 3*I across rheumatic diseases, gender and languages.MethodsParticipants with rheumatic disease from various countries completed an online study using the 3*I, which was presented in Dutch, English, French, German, Portuguese and Spanish; 6057 people with rheumatic diseases participated. Single and multiple group confirmatory factor analyses were used to test the factorial structure and measurement invariance of the 3*I with Mplus.ResultsThe model with strong measurement invariance, that is, equal factor loadings and thresholds (distribution cut-points) across gender and rheumatic disease (fibromyalgia vs other rheumatic diseases) had the best fit estimates for the Dutch version, and good fit estimates across the six language versions.ConclusionsThe 3*I showed measurement invariance across gender, rheumatic disease and language. Therefore, it is appropriate to compare and pool scores of the 3*I across groups. Future research may use the questionnaire to examine antecedents and consequences of invalidation as well as the effect of treatments targeting invalidation.

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