Linguistic validation of the DN4 for use in international studies.

OBJECTIVES: Traditionally, pain is divided into two main groups: nociceptive pain due to an excess of nociception and neuropathic pain associated with an injury or dysfunction of the central or peripheral nervous system. The French neuropathic pain group has developed a specific questionnaire, the DN4, to help clinicians in the differential diagnosis of neuropathic and non-neuropathic pain. In order to allow this questionnaire to be used in international studies, it has been translated and linguistically validated into Dutch, German, Greek and Hungarian, using a well-established procedure. METHODS: The same method was used for each country and involved four stages: (1) two forward translations followed by comparison and reconciliation of the translations, (2) one backward translation, (3) review by an expert clinician, and (4) cognitive testing of the first seven items on patients. RESULTS: The translation work produced three types of situations. Either the original wording could be translated literally or semantic issues were discussed as the original wording was not always sufficiently clear and had to be clarified by adding an explanation, or, in the case of idiomatic phrases such as "pins and needles", it was necessary to use different expressions, the challenge being to retain the original concept while doing so. The versions proposed to patients and experts were well understood. CONCLUSION: The DN4 items were linguistically validated in each of the target languages, thus providing the means for standardising the diagnosis of neuropathic pain and pooling the data collected during clinical research in the different countries involved.

Health-related quality of life in asthma studies. Can we combine data from different countries?

The aim was to compare health-related quality of life (HRQL) in patients with asthma from 4 countries, and to investigate the correlations between HRQL and clinical indices.341 patients; 140 (Sweden), 54 (Norway), 65 (the Netherlands) and 82 (Greece) were treated with formoterol fumarate 4.5 microg or with terbutaline sulphate 0.5mg for 12 weeks inhaled 'on demand' via Turbuhaler. The Asthma Quality of Life Questionnaire (AQLQ) and clinical indices were assessed. The mean baseline AQLQ overall scores in Sweden (4.97), in the Netherlands (5.04), in Norway (4.68) and in Greece (4.68) were in the same range, however, with a significant difference between the four countries (p=0.038). When comparing AQLQ, activity limitation and symptoms domains, the differences between the countries were not statistically significant. The cross-sectional correlations between AQLQ overall score and the clinical indices were similar in all four countries. The magnitude of change in AQLQ was consistent with the other clinical variables. The correlations between change in AQLQ overall score and change in clinical indices were low to medium in all countries. In conclusion, the consistency of cross-sectional correlations between the AQLQ overall and clinical indices across countries supports the validity of translations of the AQLQ used in this study. There were differences in baseline values between the countries. The treatment response in AQLQ differed to the same extent as other clinical indices. When combining HRQL data from different countries, there might be cultural, gender and socio-economic differences, explaining different responses to treatment.