A validity-driven approach to the understanding of the personal and societal burden of low back pain : development of a conceptual and measurement model

Introduction: While the importance and magnitude of the burden of low back pain upon the individual is well recognized, a systematic understanding of the impact of the condition on individuals is currently hampered by the lack of an organized understanding of what aspects of a person’s life are affected and the lack of comprehensive measures for these effects. The aim of the present study was to develop a conceptual and measurement model of the overall burden of low back pain from the individual’s perspective using a validity-driven approach.
Methods: To define the breadth of low back pain burden we conducted three concept-mapping workshops to generate an item pool. Two face-to-face workshops (Australia) were conducted with people with low back pain and clinicians and policy-makers, respectively. A third workshop (USA) was held with international multidisciplinary experts. Multidimensional scaling, cluster analysis, participant input and thematic analyses organized participants’ ideas into clusters of ideas that then informed the conceptual model.
Results: One hundred and ninety-nine statements were generated. Considerable overlap was observed between groups, and four major clusters were observed - Psychosocial, Physical, Treatment and Employment - each with between two and six subclusters. Content analysis revealed that elements of the Psychosocial cluster were sufficiently distinct to be split into Psychological and Social, and a further cluster of elements termed Positive Effects also emerged. Finally, a hypothesized structure was proposed with six domains and 16 subdomains. New domains not previously considered in the back pain field emerged for psychometric verification: loss of independence, worry about the future, and negative or discriminatory actions by others.
Conclusions: Using a grounded approach, an explicit a priori and testable model of the overall burden of low back pain has been proposed that captures the full breadth of the burden experienced by patients and observed by experts.

Continuous corrosion rate measurement by noise resistance calculation

A commonly employed method of corrosion rate measurement is to determine the electrochemical impedance of the corroding material. One technique for estimating the impedance is the noise impedance calculation. While it has been shown to yield useful results, there are a number of problems that require attention. This paper identifies some of those problems-specifically, those of detrending and resolution-and provides a solution that allows continuous, time-varying noise resistance and noise impedance calculations to be performed with known time, frequency, and magnitude resolutions. Applications to synthetic and experimental data are included as illustrations