The Portuguese Rheumatoid Arthritis Impact of Disease (RAID) score and its measurement equivalence in three countries: validation study using Rasch Models

© 2018, The Author(s). Purpose: The Rheumatoid Arthritis Impact of Disease (RAID) score assesses seven impact domains of interest for people with RA. This study aimed to test patients’ understanding of the Portuguese RAID and evaluate its cross-cultural validity for use in Portugal. Methods: This was a mixed methods study comprising two phases: (i) cognitive debriefing to determine patient’s comprehension of the Portuguese RAID and (ii) cross-cultural validation using Rasch analysis. Construct validity was determined by fit to the model, invariance culture (compared with France and UK datasets) and evidence of convergent and divergent validity. Results: Patients’ input (n = 38) led to minor changes in the phrasing of two items to ensure conceptual equivalence between the Portuguese and the original RAID. In Rasch analysis (n = 288), two items ‘Sleep’ and ‘Physical well-being’ in the Portuguese dataset did not adequately fit the model specifications, suggesting multidimensionality (sleep—not necessarily associated with RA) and redundancy (physical well-being overlapping with functional disability). Despite the imperfections, the scale had high internal consistency, evidence of convergent and divergent validity and invariance to culture (compared to France n = 195 and UK n = 205 datasets). The scale was well targeted for patients with different levels of disease impact. Conclusions: The RAID has been successfully adapted into Portuguese and it can be used with confidence in clinical practice. Further research will be required to ensure it captures the full range of sleep problems in RA. Meanwhile, data across the three countries (Portugal, France and the UK) are comparable except for the two items (sleep and physical well-being)

Fatigue testing of a NiTi rotary instrument. Part 1: Strain-life relationship

Aim To examine the fatigue behaviour using a strain-life approach, and to determine the effect of water on the fatigue life of a NiTi rotary instrument. Methodology Instruments of one brand of NiTi engine-file (size 25, ProFile 0.04 and 0.06) were subjected to rotational bending either in air or under water, the number of revolutions to fracture (Nf) being recorded using an optical counter and an electronic break-detection circuit. The effective surface strain amplitude (εa) for each specimen was determined from the curvature of the instrument (on a photograph) and the diameter of the fracture cross-section (from a scanning electron micrograph of the fracture surface). Strain was plotted against fatigue life and the low-cycle fatigue (LCF) region identified. Values were examined using two-way analysis of variance for difference between various instrument-environment combinations. Results A total of 212 instruments were tested. A strain-life relationship typical of metals was found. Nf declined with an inverse power function dependence on εa. A fatigue limit was present at about 0.7% strain. The apparent fatigue-ductility exponent, a material constant for the LCF life of metals, was found to be between -0.45 and -0.55. There was a significant effect of the environmental condition on the LCF life, water being more detrimental than air. Conclusions The fatigue behaviour of NiTi rotary instrument is typical of most metals, provided that the analysis is based on the surface strain amplitude, and showed a high-cycle and a LCF region. The LCF life is adversely affected by water. © 2007 International Endodontic Journal.link_to_subscribed_fulltex