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.

AIMS: To compare two versions of a questionnaire translated using forward-backward (FB) translation and dual-panel (DP) methodologies regarding preference of wording and psychometric properties.

METHODS: The Rheumatoid Arthritis Quality of Life instrument was adapted into Swedish by two independent groups using FB and DP methodologies, respectively. Seven out of thirty resulting items were identical. Nonidentical items were evaluated regarding preference of wording by 23 bilingual Swedes, 50 people with rheumatoid arthritis (RA), and 2 lay panels (n = 11). Psychometric performance was assessed from a postal survey of 200 people with RA randomly assigned to complete one version first and the other 2 weeks later.

RESULTS: Preference did not differ among the 23 bilinguals (P = 0.196), whereas patients and lay people preferred DP over FB item versions (P < 0.0001). Postal survey response rates were 74% (FB) and 75% (DP). There were more missing item responses in the FB than the DP version (6.9% vs. 5.6%; P < 0.0001). Floor/ceiling effects were small (FB, 6.1/0%; DP, 4.4/0.7%) and reliability was 0.92 for both versions. Construct validity was similar for both versions. Differential item functioning by version was detected for five items but cancelled out and did not affect estimated person measures.

CONCLUSIONS: The DP approach showed advantages over FB translation in terms of preference by the target population and by lay people, whereas there were no obvious psychometric differences. This suggests advantages of DP over FB translation from the patients' perspective, and does not support the commonly held view that FB translation is the "gold standard."

OBJECTIVES: Patient-reported health status questionnaires intend to assess illness and therapy from the patients' perspective. To provide fair and valid assessments, they should be equally relevant to major subsets of respondents. Furthermore, disease-specific measures are assumed to be perceived as more relevant than generic ones. This study assessed these assumptions among people with Parkinson's disease.

METHODS: Cross-sectional data from 202 people with Parkinson's disease (54% men; mean age, 70) were analyzed regarding patient-rated relevance and predictors of patient-rated poor relevance of two generic [the 36-item Short Form Health Survey (SF-36) and Nottingham Health Profile (NHP)] and one disease-specific [Parkinson's Disease Questionnaire (PDQ-39)] health status questionnaire.

RESULTS: There were no differences in relevance ratings across the questionnaires. Poorer overall quality of life [odds ratio (OR), 2.459] and mental health (OR, 1.023) were associated with poorer patient-rated relevance of the SF-36, and higher age was associated with poorer patient-rated relevance of the PDQ-39 (OR, 1.040). No significant predictors were found for the NHP.

CONCLUSIONS: The PDQ-39 failed to meet the assumption that disease-specific scales are more relevant than generic ones. Nevertheless, the most important implication of this study is an ethical one. Because the relevance of the SF-36 and PDQ-39 is perceived as poorer by those who fare least well and by older people, these scales may not reflect the perspectives of these groups. This challenges bioethical principles and threatens scientific validity. Perceived relevance of patient-centered outcomes needs to be considered, or the voice of vulnerable groups may be silenced, fair inferences prohibited, and opportunities for improved care lost.

BACKGROUND: The Patient-Reported Indices for Multiple Sclerosis (PRIMUS) comprises a suite of three scales for assessing symptoms, activity limitations, and quality of life in multiple sclerosis (MS). It was developed in the UK and has been shown to have excellent psychometric properties. This study describes the adaptation of eight language versions for Canadian English, Canadian French, French, German, Italian, Spanish, Swedish, and US English.

METHODS: The PRIMUS was translated using the dual-panel process. Cognitive debriefing interviews conducted with MS patients assessed face and content validity. Psychometric and scaling properties were assessed via a two-administration postal survey conducted in each country involving the PRIMUS, the Nottingham Health Profile (NHP), the Unidimensional Fatigue Impact Scale (U-FIS), and demographic questions.

RESULTS: Cognitive debriefing interviews demonstrated the acceptability of the new language versions. Analysis of survey data showed that the new language versions of the three PRIMUS scales were unidimensional (as indicated by fit to the Rasch model) and that they had good internal consistency and reproducibility. PRIMUS scale scores correlated as expected with those on the NHP and the U-FIS. The scales in all countries were able to discriminate between groups of patients on the basis of their self-reported MS severity, general health, and employment status.

CONCLUSIONS: The PRIMUS was successfully adapted into eight new languages. Most of the tests showed the PRIMUS to have good unidimensionality and to have good internal consistency, reproducibility, and construct validity. The measure is now available for use in clinical studies and trials involving these countries and the UK. Further work is required to assess the measure's responsiveness.

Due to the international nature of many clinical studies and trials it is often necessary to produce several language versions of specific measures. While it is generally acknowledged that it is necessary to produce versions that are conceptually equivalent, the best method of achieving this is more controversial. It is commonly stated that there is a gold-standard method, which involves forward and backward translation. However, no evidence has been presented to support this view. This paper argues that the "gold-standard" method is difficult to support and describes an alternative method involving dual translation panels that has been used in the production of all adaptations of needs-based quality of life instruments.

This paper discusses recent advances that have been made in the field of psychometrics, specifically, the application of Rasch analysis to the instrument development process. It emphasizes the importance of assessing the fundamental scaling properties of an instrument prior to consideration of traditional psychometric indicators. The paper introduces Rasch analysis and shows how it has been applied in the development of needs-based measures in order to ensure that they provide unidimensional measurement. By ensuring that scales are based on the same measurement model and that they fit the Rasch model it is possible for QoL scores to be compared across diseases by means of cocalibration and item banking.