Measuring disease impact in disabling neurological conditions: are patients' perspectives and scientific rigor compatible?

PURPOSE OF REVIEW: Increasing emphasis on the measurement of patient-based outcomes has highlighted the importance of measuring patients' perspectives as rigorously as possible. Therefore, patients' perspectives and scientific rigor must be compatible. This review examines recent information in the area of quantifying patients' perspectives. RECENT FINDINGS: There have been developments in two main areas. First, the application of traditional psychometric methods. Second, the application of new psychometric methods for data analysis, that is, Rasch analysis and Item Response Theory. SUMMARY: The use of traditional psychometric methods results in more reliable and valid rating scales for measuring patient-based outcomes. Whilst it is encouraging that traditional methods are being used, there is still a greater need for examinations that address all psychometric properties, head-to-head comparisons of scales, and the use of these methods during the construction of scales. The application of Rasch analysis and item response theory offers the opportunity to take health measurement to a higher plane, interval level measurement. However, only Rasch analysis appears to enable 'fundamental measurement', the type of measurement taken for granted in the physical sciences.