A multilevel item response theory model was investigated for longitudinal vision-related quality-of-life data

ObjectiveTo investigate how a multilevel item response theory (IRT) model for longitudinal dependent data could provide average and individual quality-of-life outcomes of low-vision rehabilitation.Study Design and SettingIn a nonrandomized longitudinal design, visually impaired older patients (n = 296) were referred to multidisciplinary rehabilitation or to an optometric service. The five-dimensional Low Vision Quality of Life Questionnaire was administered at four time points. The IRT model was characterized by the graded response model for rating scales. Covariates were added to the model, mainly to correct for missing data. The invariance assumption across time points was investigated.ResultsAverage and individual rehabilitation effects were estimated. For multidisciplinary rehabilitation, significant average deterioration was seen on three dimensions after 4.4 years. Many individuals in the optometric service group significantly improved on the “reading small print” dimension (18.5%); in both groups, many individuals significantly deteriorated on “visual (motor) skills” (22.2–30.0%). Invariance across time points could be assumed for all dimensions, except for “adjustment.” Gender, education, visual acuity, and health status were significantly associated with the outcome.ConclusionWe present how a multilevel IRT model can be applied to describe longitudinal dependent vision-related quality-of-life data, while focusing on average and individual effects.     

Assessing pain and pain-related fear in acute low back pain: what is the smallest detectable change?

Background: The Tampa Scale for Kinesiophobia (TSK) and the Fear-Avoidance Beliefs Questionnaire (FABQ) are frequently used questionnaires for pain-related fear, and the visual analogue scale (VAS) is for pain. Purpose: This study aims to determine the smallest detectable change (SDC) of these questionnaires in patients with acute low back pain (LBP), as well as ceiling and/or floor effects. Results: The SDC for the TSK (scoring range: 17–68) was 9.2 (95% CI: 8.4; 10.3). The estimated SDC was 9.4 (95% CI: 8.5; 10.6) and 12.7 (95% CI: 11.5; 14.1) for the FABQphysical activity subscale (scoring range: 0–24) and/or work subscale (scoring range: 0–42), respectively. For the VAS for pain (0–100 mm), the SDC turned out to be 36.2 mm (95% CI: 32.4; 41.0). The FABQ physical activity subscale and pain (VAS) seem to have considerable problems in detecting improvement and deterioration. The TSK appears to be able to detect improvement as well as deterioration. Conclusion: The SDCs of the (subscales of) questionnaires range from 18% to 40%. Floor and/or ceiling effects were detected for most scales, except the TSK total and the TSK activity avoidance subscale. These results should be considered when using these questionnaires as measures of therapeutic change in acute LBP.     

Protocol of the COSMIN study: COnsensus-based Standards for the selection of health Measurement INstruments

Background  

Choosing an adequate measurement instrument depends on the proposed use of the instrument, the concept to be measured, the measurement properties (e.g. internal consistency, reproducibility, content and construct validity, responsiveness, and interpretability), the requirements, the burden for subjects, and costs of the available instruments. As far as measurement properties are concerned, there are no sufficiently specific standards for the evaluation of measurement properties of instruments to measure health status, and also no explicit criteria for what constitutes good measurement properties. In this paper we describe the protocol for the COSMIN study, the objective of which is to develop a checklist that contains COnsensus-based Standards for the selection of health Measurement INstruments, including explicit criteria for satisfying these standards. We will focus on evaluative health related patient-reported outcomes (HR-PROs), i.e. patient-reported health measurement instruments used in a longitudinal design as an outcome measure, excluding health care related PROs, such as satisfaction with care or adherence. The COSMIN standards will be made available in the form of an easily applicable checklist.     

Methodological considerations for improving the reproducibility of walking efficiency outcomes in clinical gait studies

In recent clinical gait studies, the use of net energy cost (EC) outcomes has been recommended. This study assessed the comparative reproducibility of gross and net EC of walking in adults and children with locomotion disorders, using a portable system for gas-exchange. Furthermore, methodological considerations were proposed for improving the reproducibility of these outcomes. Assessment of reproducibility was made in adults with polio residuals (n=14) versus healthy adults (n=14), and in children with cerebral palsy (n=13) versus healthy children (n=10). There were four repeated measurement sessions on different days, with inter-session periods of 1 week. All the measurements had been conducted at the outpatient clinic between 2002 and 2004. Based on the Generalizability Theory for data-analysis, it was shown that there was less intra-subject variability in gross EC of walking compared to net EC of walking among adults and children with locomotion disorders, which was apparent from the lower standard error of measurement values. Data-analysis optimisation and study design adjustments were considered and presented in a decision scheme, to demonstrate that the reproducibility of net EC can substantially be increased. The use of gross EC, rather than net EC, in patients with locomotion disorders seems a more reproducible measure of walking efficiency. However, reproducibility of net EC can substantially be improved by careful standardization and using a multiple repetition design, as a result of which this outcome measure becomes suitable for detecting clinically relevant changes at the individual level.