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Background Scores on an outcome measurement instrument depend on the type and settings of the instrument used, how instructions are given to patients, how professionals administer and score the instrument, etc. The impact of all these sources of variation on scores can be assessed in studies on reliability and measurement error, if properly designed and analyzed. The aim of this study was to develop standards to assess the quality of studies on reliability and measurement error of clinician-reported outcome measurement instruments, performance-based outcome measurement instrument, and laboratory values. Methods We conducted a 3-round Delphi study involving 52 panelists. Results Consensus was reached on how a comprehensive research question can be deduced from the design of a reliability study to determine how the results of a study inform us about the quality of the outcome measurement instrument at issue. Consensus was reached on components of outcome measurement instruments, i.e. the potential sources of variation. Next, we reached consensus on standards on design requirements ( n  = 5), standards on preferred statistical methods for reliability ( n  = 3) and measurement error ( n  = 2), and their ratings on a four-point scale. There was one term for a component and one rating of one standard on which no consensus was reached, and therefore required a decision by the steering committee. Conclusion We developed a tool that enables researchers with and without thorough knowledge on measurement properties to assess the quality of a study on reliability and measurement error of outcome measurement instruments.

Purpose The original COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) checklist was developed to assess the methodological quality of single studies on measurement properties of Patient-Reported Outcome Measures (PROMs). Now it is our aim to adapt the COSMIN checklist and its four-point rating system into a version exclusively for use in systematic reviews of PROMs, aiming to assess risk of bias of studies on measurement properties. Methods For each standard (i.e., a design requirement or preferred statistical method), it was discussed within the COSMIN steering committee if and how it should be adapted. The adapted checklist was pilot-tested to strengthen content validity in a systematic review on the quality of PROMs for patients with hand osteoarthritis. Results Most important changes were the reordering of the measurement properties to be assessed in a systematic review of PROMs; the deletion of standards that concerned reporting issues and standards that not necessarily lead to biased results; the integration of standards on general requirements for studies on item response theory with standards for specific measurement properties; the recommendation to the review team to specify hypotheses for construct validity and responsiveness in advance, and subsequently the removal of the standards about formulating hypotheses; and the change in the labels of the four-point rating system. Conclusions The COSMIN Risk of Bias checklist was developed exclusively for use in systematic reviews of PROMs to distinguish this application from other purposes of assessing the methodological quality of studies on measurement properties, such as guidance for designing or reporting a study on the measurement properties.

Background Content validity is the most important measurement property of a patient-reported outcome measure (PROM) and the most challenging to assess. Our aims were to: (1) develop standards for evaluating the quality of PROM development; (2) update the original COSMIN standards for assessing the quality of content validity studies of PROMs; (3) develop criteria for what constitutes good content validity of PROMs, and (4) develop a rating system for summarizing the evidence on a PROM's content validity and grading the quality of the evidence in systematic reviews of PROMs. Methods An online 4-round Delphi study was performed among 159 experts from 21 countries. Panelists rated the degree to which they (dis)agreed to proposed standards, criteria, and rating issues on 5-point rating scales ('strongly disagree' to 'strongly agree'), and provided arguments for their ratings. Results Discussion focused on sample size requirements, recording and field notes, transcribing cognitive interviews, and data coding. After four rounds, the required 67% consensus was reached on all standards, criteria, and rating issues. After pilot-testing, the steering committee made some final changes. Ten criteria for good content validity were defined regarding item relevance, appropriateness of response options and recall period, comprehensiveness, and comprehensibility of the PROM. Discussion The consensus-based COSMIN methodology for content validity is more detailed, standardized, and transparent than earlier published guidelines, including the previous COSMIN standards. This methodology can contribute to the selection and use of high-quality PROMs in research and clinical practice.

Purpose The Patient and Observer Scar Assessment Scale (POSAS) is widely used for measurements of scar quality . This encompasses visual, tactile and sensory characteristics of the scar. The Patient Scale of previous POSAS versions was lacking input from patients. Therefore, the aim of this study was to develop the POSAS3.0, Patient Scale with involvement of adults patients with all scar types, complying with the highest clinimetric standards. Methods From February 2018 to April 2019, a series of six focus group interviews were performed in the Netherlands and Australia to identify scar quality characteristics that adults with scars consider to be important. All focus groups were transcribed, anonymized and analysed using a thematic analysis. Relevant characteristics were formulated into items, resulting in a Dutch and English version of the Patient Scale. These drafts were pilot tested in Australia, the Netherlands and the United Kingdom, and refined accordingly. Results A total of 21 relevant scar quality characteristics were identified during the focus groups. Two distinct versions of the POSAS3.0, Patient Scale were developed. The Generic version contains 16 items and can be used for all scar types, except linear scars. The Linear Scar version of the Patient Scale contains the same 16 items, with an extra item referring to the widening of scar margins. All included items are rated on a verbal rating scale with five response options. Conclusion Two versions of the POSAS3.0 Patient Scale were developed. Further field tests are being performed to establish the measurement properties and scoring algorithm of the scales.

Research on depression stigma is needed to gain more insight into the underlying construct and to reduce the level of stigma in the community. However, few validated measurements of depression stigma are available in the Netherlands. Therefore, this study first sought to examine the psychometric properties of the Dutch translation of the Depression Stigma Scale (DSS). Second, we examined which demographic (gender, age, education, partner status) and other variables (anxiety and knowledge of depression) are associated with personal and perceived stigma within these samples. The study population consisted of an adult convenience sample (n = 253) (study 1) and a community adult sample with elevated depressive symptoms (n = 264) (study 2). Factor structure, internal consistency, and validity were assessed. The associations between stigma, demographic variables and anxiety level were examined with regression analyses. Confirmatory factor analysis supported the validity and internal consistency of the DSS personal stigma scale. Internal consistency was sufficient (Cronbach's alpha = .70 (study 1) and .77 (study 2)). The results regarding the perceived stigma scale revealed no clear factor structure. Regression analyses showed that personal stigma was higher in younger people, those with no experience with depression, and those with lower education. This study established the validity and internal consistency of the DSS personal scale in the Netherlands, in a community sample and in people with elevated depressive symptoms. However, additional research is needed to examine the factor structure of the DSS perceived scale and its use in other samples.

Content validity is key when developing a new outcome measurement instrument or selecting an existing measurement instrument. Without good content validity, wrong conclusions can be drawn about an outcome that is measured. In this article, we explain that content validity refers to the relevance, comprehensiveness, and comprehensibility of the instruments' content. Content validity is not only relevant for patient-reported outcome measures but also for other outcome measurement instruments, such as clinician-reported outcome measures and performance-based tests. It is preferably assessed in qualitative studies, eg, focus group studies or Delphi studies. When developing an instrument, the focus is first on the relevance and comprehensiveness of the content of the instrument, then the content is developed, and next its comprehensibility is evaluated. Steps may be repeated. When evaluating content validity of an existing measurement instrument, the three aspects of content validity are evaluated at the same time. Content validity helps to understand whether the content of the measurement instrument is a sufficient representation of the outcome being measured (relevance and comprehensiveness), and whether the formulation used in the measurement instrument (eg, to describe instructions, items, tasks, explanations) is sufficiently understood (comprehensibility) by the people involved in the measurement.

Purpose Systematic reviews of patient-reported outcome measures (PROMs) differ from reviews of interventions and diagnostic test accuracy studies and are complex. In fact, conducting a review of one or more PROMs comprises of multiple reviews (i.e., one review for each measurement property of each PROM). In the absence of guidance specifically designed for reviews on measurement properties, our aim was to develop a guideline for conducting systematic reviews of PROMs. Methods Based on literature reviews and expert opinions, and in concordance with existing guidelines, the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) steering committee developed a guideline for systematic reviews of PROMs. Results A consecutive ten-step procedure for conducting a systematic review of PROMs is proposed. Steps 1-4 concern preparing and performing the literature search, and selecting relevant studies. Steps 5-8 concern the evaluation of the quality of the eligible studies, the measurement properties, and the interpretability and feasibility aspects. Steps 9 and 10 concern formulating recommendations and reporting the systematic review. Conclusions The COSMIN guideline for systematic reviews of PROMs includes methodology to combine the methodological quality of studies on measurement properties with the quality of the PROM itself (i.e., its measurement properties). This enables reviewers to draw transparent conclusions and making evidence-based recommendations on the quality of PROMs, and supports the evidence-based selection of PROMs for use in research and in clinical practice.

Any measurement starts with determining what to measure (ie, which outcome) and how to measure it (ie, which outcome measurement instrument). This article is the first from a series of the COnsensus-based Standards for the selection of health Measurement INstruments perspective in which we will explain measurements and how to evaluate measurement quality. In this first perspective, we explain the rationale for defining an outcome and operationalizing it into an outcome measurement instrument. An outcome should first be defined based on theory, and next be operationalized into one or more observable items, questions, tasks or parameters. But a measurement instrument is more than its items or machine. Any type of measurement instrument consist of 5 components: (1) equipment, (2) preparatory actions, (3) unprocessed data collection or collection of the biological sample(s), (4) processing and storage, and (5) assignment of the score or determination of the value of the biological sample. Thinking in terms of the components of measurement instruments can enhance the design and understanding of studies on measurement properties.

Purpose The aims were to evaluate the construct validity and reliability of the Dutch version of the pediatric-modified Total Neuropathy Score (ped-mTNS) for assessing vincristine-induced peripheral neuropathy (VIPN) in Dutch pediatric oncology patients aged 5–18 years. Methods Construct validity (primary aim) of the ped-mTNS was determined by testing hypotheses about expected correlation between scores of the ped-mTNS (range: 0–32) and the Common Terminology Criteria for Adverse Events (CTCAE) (range: 0–18) for patients and healthy controls and by comparing patients and controls regarding their total ped-mTNS scores and the proportion of children identified with VIPN. Inter-rater and intra-rater reliability and measurement error (secondary aims) were assessed in a subgroup of study participants. Results Among the 112 children (56 patients and 56 age- and gender-matched healthy controls) evaluated, correlation between CTCAE and ped-mTNS scores was as expected (moderate ( r = 0.60)). Moreover, as expected, patients had significantly higher ped-mTNS scores and more frequent symptoms of VIPN compared with controls (both p < .001). Reliability as measured within the intra-rater group ( n = 10) (intra-class correlation coefficient (ICC agreement ) = 0.64, standard error of measurement (SEM agreement ) = 2.92, and smallest detectable change (SDC agreement ) = 8.1) and within the inter-rater subgroup ( n = 10) (ICC agreement = 0.63, SEM agreement = 3.7, and SDC agreement = 10.26) indicates insufficient reliability. Conclusion The Dutch version of the ped-mTNS appears to have good construct validity for assessing VIPN in a Dutch pediatric oncology population, whereas reliability appears to be insufficient and measurement error high. To improve standardization of VIPN assessment in children, future research aimed at evaluating and further optimizing the psychometric characteristics of the ped-mTNS is needed.

Background: Guy’s Neurological Disability Scale (GNDS) is designed to assess disability (i.e. activity limitations) in patients with multiple sclerosis. It contains 12 functional domains, each indicating a level of disability. Four domain scores and a total score can be calculated. Objective: The aim of this study was to evaluate the structural validity of the GNDS in a Dutch population who were definitely diagnosed as having multiple sclerosis. Methods: Data of 974 patients were available. The structural validity of the GNDS was evaluated by confirmatory item factor analysis (CIFA). Two first-order models and two bifactor models were investigated. Results: The best fitted model was a bifactor model with a general factor underlying all items, and 10 items loading on 3 group factors. Cronbach’s alpha on the general factor (0.78) and on the group factor spinal-plus (0.74) were satisfying. Cronbach’s alpha on the group factors mental (0.56) and bulbar (0.48) were low. Reliability based on CIFA was 0.85. Conclusion: Results showed a clear factor structure of the GNDS. It justifies the use of the total score of the GNDS. In addition, three sub-scale scores could be used.