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Objective: The 22-item Unidimensional Fatigue Impact Scale (U-FIS) provides an index of the impact of fatigue on patients with multiple sclerosis (MS). The objective is to produce eight new language versions of the U-FIS: Canadian-English, Canadian-French, French, German, Italian, Spanish, Swedish, and US-English., Methods: The U-FIS was translated via two translation panels. Cognitive debriefing interviews conducted with patients in each country assessed face and content validity. Scaling and psychometric properties were assessed via survey data with patients in each country completing the U-FIS, Nottingham Health Profile (NHP), and demographic questions., Results: Cognitive debriefing interviews demonstrated U-FIS acceptability. Analysis of postal survey data showed all new language versions to be unidimensional. Reliability was high, with test-retest correlations and internal-consistency coefficients exceeding 0.85. Initial evidence of validity was provided by moderate to high correlations with NHP scales. The U-FIS was able to discriminate between groups based on employment status, perceived MS severity, and general health., Conclusion: The U-FIS is a practical new measure of the impact of fatigue. It was successfully adapted into eight new languages to broaden availability for researchers. Psychometric analyses indicated that the new language versions were unidimensional and reproducible with promising construct validity.

The dermatology life questionnaire index (DLQI) and the Skindex are the most commonly used dermatology-specific health-related quality of life (HRQOL) instruments. Although these tools are used in international surveys and clinical trials, the cross-cultural equivalence of their items has not been documented. We used differential item functioning (DIF), which is part of the Rasch model, to assess the impact of cultural background on the items of the DLQI and Skindex-29 and-17. The data of the 450 psoriasis patients, who attended in- and outpatient dermatology centers, was collected retrospectively from five European and one US center. The DLQI and Skindex-29 scales did not fit the Rasch model (P<0.0008) and 10/10 of the DLQI and 19/29 of the Skindex-29 items displayed significant DIF. Although the psychosocial scale of the Skindex-17 fitted the Rasch model, half or more of the items of the psychosocial (6/12) and the symptom scale (4/5) showed significant DIF across countries. These findings suggest that psoriasis patients from different countries respond differently to a substantial proportion of DLQI and Skindex items despite having the same level of underlying HRQOL impairment. Therefore, these instruments should not be used in their current form in international studies.

Background: A previous study had identified 45 items assessing the impact of atopic dermatitis (AD) on the whole family. From these it was intended to develop two separate scales, one assessing impact on carers and the other determining the effect on the child., Methods: The 45 items were included in three clinical trials designed to test the efficacy of a new topical treatment (pimecrolimus, Elidel cream 1%) in the treatment of AD in infants and children and in validation studies in the UK, US, Germany, France and the Netherlands. Rasch analyses were undertaken to determine whether an internationally valid, unidimensional scale could be developed that would inform on the direct impact of AD on the child., Results: Rasch analyses applied to the data from the trials indicated that the draft measure consisted of two scales, one assessing the QoL of the carer and the other (consisting of 12 items) measuring the impact of AD on the child. Three of the 12 potential items failed to fit the measurement model in Europe and five in the US. In addition, four items exhibiting differential item functioning (DIF) by country were identified. After removing the misfitting items and controlling for DIF it was possible to derive a scale; The Childhood Impact of Atopic Dermatitis (CIAD) with good item fit for each trial analysis. Analysis of the validation data from each of the different countries confirmed that the CIAD had adequate internal consistency, reproducibility and construct validity. The CIAD demonstrated the benefits of treatment with Elidel over placebo in the European trial. A similar (non-significant) trend was found for the US trials., Conclusion: The study represents a novel method of dealing with the problem of DIF associated with different cultures. Such problems are likely to arise in any multinational study involving patient-reported outcome measures, as items in the scales are likely to be valued differently in different cultures. However, where all items in a scale fit both a single theoretical construct and the Rasch measurement model, it is feasible to conceive of outcome measures with a different set of items in each language.

Background: The Ankylosing Spondylitis Quality of Life (ASQOL) questionnaire is a unidimensional, disease-specific measure developed in the UK and the Netherlands. This study describes its adaptation into other languages., Methods: The UK English ASQOL was translated into US English; Canadian French and English; French; German; Italian; Spanish; and Swedish (dual-panel methods). Cognitive debriefing interviews were conducted with AS patients. Psychometric/scaling properties were assessed using data from two Phase III studies of adalimumab. Baseline and Week-2 data were used to assess test-retest reliability. Validity was determined by correlation of ASQOL with SF-36 and BASFI and by discriminative ability of ASQOL based on disease severity. Item response theory (Rasch model) was used to test ASQOL's scaling properties., Results: Cognitive debriefing showed the new ASQOL versions to be clear, relevant and comprehensive. Sample sizes varied, but were sufficient for: psychometric/scaling assessment for US English and Canadian English; psychometric but not scaling analyses for German; and preliminary evidence of these properties for the remaining languages. Test-retest reliability and Cronbach's alpha coefficients were high: US English (0.85, 0.85), Canadian English (0.87, 0.86), and German (0.77, 0.79). Correlations of ASQOL with SF-36 and BASFI for US English, Canadian English, and German measures were moderate, but ASQOL discriminated between patients based on perceived disease severities (p < 0.01). Results were comparable for the other languages. US English and Canadian English exhibited fit to the Rasch model (non-significant p-values: 0.54, 0.68), confirming unidimensionality., Conclusion: The ASQOL was successfully translated into all eight languages. Psychometric properties were excellent for US English, Canadian English, and German, and extremely promising for the other languages.