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Considers tests of unidimensionality in polytomous Rasch models against a specified alternative, given by a partition of the items into subgroups, that are believed to measure different dimensions of the latent construct. Uses data from an occupational health study to motivate and illustrate the methods. (SLD)

Background: Patients with rheumatoid arthritis (RA) commonly experience pain despite the availability of disease-modifying treatments. Sleep disturbances are frequently reported in RA, with pain often a contributing factor. The Patient-Reported Outcomes Measurement Information System (PROMIS) Pain Interference and Sleep Disturbance item banks were initially developed to provide insights into the patient experience of pain and sleep, respectively, though they were not specifically intended for use in RA populations. This study evaluated the content validity of the PROMIS Pain Interference and Sleep Disturbance item banks in RA and identified relevant content for short forms for patients with RA that achieved high measurement precision across a broad range of health. Methods: A qualitative approach consisting of hybrid concept elicitation and cognitive debriefing interviews was used to evaluate the content validity of the item banks in RA. Interviews were semi-structured and open-ended, allowing a range of concepts and responses to be captured. Findings from the qualitative interviews were used to select the most relevant items for the short forms, and psychometric evaluation, using existing item-response theory (IRT) item parameters, was used to evaluate the marginal reliability and measurement precision of the short forms across the range of the latent variables (i.e. pain interference and sleep disturbance). Results: Thirty-two participants were interviewed. Participants reported that RA-related pain and sleep disturbances have substantial impacts on their daily lives, particularly with physical functioning. The PROMIS Pain Interference and Sleep Disturbance item banks were easy to understand and mostly relevant to their RA experiences, and the 7-day recall period was deemed appropriate. Qualitative and IRT-based approaches identified short forms for Pain Interference (11 items) and Sleep Disturbance (7 items) that had high relevance and measurement precision, with good coverage of the concepts identified by participants during concept elicitation. Conclusion: Pain and sleep disturbances affect many aspects of daily life in patients with RA and should be considered when novel treatments are developed. This study supports the use of the PROMIS Pain Interference and Sleep Disturbance item banks in RA, and the short forms developed herein have the potential to be used in clinical studies of RA. [ABSTRACT FROM AUTHOR]

Purpose: This paper presents two studies exploring the latent structure of item sets used in the development of the Recovering Quality of Life mental health outcome measures: ReQoL-10 and ReQoL-20.Method: In study 1, 2262 participants completed an initial set of 61 items. In study 2, 4266 participants completed a reduced set of 40 items. Study 2 evaluated two formats of the questionnaires: one version where the items were intermingled and one where the positively worded and negatively worded items were presented as two separate blocks. Exploratory and confirmatory factor analyses were conducted on both datasets where models were specified using ordinal treatment of the item responses. Dimensionality based on the conceptual framework and methods effects reflecting the mixture of positively worded and negatively worded items were explored. Factor invariance was tested across the intermingled and block formats.Results: In both studies, a bi-factor model (study 1: RMSEA = 0.061; CFI = 0.954; study 2: RMSEA = 0.066; CFI = 0.971) with one general factor and two local factors (positively worded questions and negatively worded questions) was preferred. The loadings on the general factor were higher than on the two local factors suggesting that the ReQoL scale scores can be understood in terms of a general factor. Insignificant differences were found between the intermingled and block formats.Conclusions: The analyses confirmed that the ReQoL item sets are sufficiently unidimensional to proceed to item response theory analysis. The model was robust across different ordering of positive and negative items. [ABSTRACT FROM AUTHOR]

Background: Thyroid diseases affect quality of life (QoL). The Thyroid-Related Patient-Reported Outcome (ThyPRO) is an international comprehensive well-validated patient-reported outcome, measuring thyroid-related QoL. The current version is rather long-85 items. The purpose of the present study was to develop an abbreviated version of the ThyPRO, with conserved good measurement properties. Methods: A cross-sectional ( N = 907) and a longitudinal sample ( N = 435) of thyroid patients were analyzed. A graded item response theory (IRT) model was fitted to the cross-sectional data. Short-form scales with three items were aimed for, by selecting items with best fit according to the IRT model, avoiding cross-culturally noninvariant items. Seven scales measuring mental and social well-being and function as well as one overall QoL impact item were analyzed in a bifactor model, to develop a supplementary composite score. Short-form scales were linked to original scales with IRT-based summed-score-linking. Agreement between the short and long form was estimated by agreement plots, intraclass correlations, and mean score levels. Responsiveness was compared by relative validity indices, clinical validity by ability to detect clinically relevant differences, and test-retest reliability by intra-class correlation. Results: One four-item scale was not abbreviated and one two-item scale was omitted from the short-form. For the 11 scales undergoing abbreviation, 10 with three and one with four items were developed. A bifactor model with good overall fit was fitted to the composite score, including the single QoL item. Responsiveness and clinical validity of the short-form scales were preserved, as were test-retest reliability (0.75-0.89). Short- versus long-form intraclass correlations were high (0.89-0.98), and the mean scale levels were similar. Conclusions: A 39-item version of the ThyPRO, with good measurement properties, was developed and is recommended for clinical use. [ABSTRACT FROM AUTHOR]

Background: There are increasing concerns about the appropriateness of generic preference-based measures to capture health benefits in the area of mental health.Objectives: The aim of this study is to estimate preference weights for a new measure, Recovering Quality of Life (ReQoL-10), to better capture the benefits of mental healthcare.Methods: Psychometric analyses of a larger sample of mental health service users (n = 4266) using confirmatory factor analyses and item response theory were used to derive a health state classification system and inform the selection of health states for utility assessment. A valuation survey with members of the UK public representative in terms of age, sex, and region was conducted using face-to-face interviewer administered time-trade-off with props. A series of regression models were fitted to the data and the best performing model selected for the scoring algorithm.Results: The ReQoL-Utility Index (UI) classification system comprises 6 mental health items and 1 physical health item. Sixty-four health states were valued by 305 participants. The preferred model was a random effects model, with significant and consistent coefficients and best model fit. Estimated utilities modeled for all health states ranged from -0.195 (state worse than dead) to 1 (best possible state).Conclusions: The development of the ReQoL-UI is based on a novel application of item response theory methods for generating the classification system and selecting health states for valuation. Conventional time-trade-off was used to elicit utility values that are modeled to enable the generation of QALYs for use in cost-utility analysis of mental health interventions. [ABSTRACT FROM AUTHOR]

Objectives. To describe the development and evaluation of the Pain Impact Questionnaire (PIQ-6TM), a six-item measure of pain severity and impact on health-related quality of life (HRQOL) domains. Participants. Two general US population samples (N = 829 and N = 7,025) and one chronic pain patient sample (N = 350) were included. Methods. The PIQ-6TM was developed using conventional and item response theory (IRT) methods in four steps: 1) initial selection and development of items based on results from a previously developed Bodily Pain item bank; 2) final item selection based on new data and investigations of unidimensionality, differential item functioning (DIF), and IRT modeling; 3) development of scoring algorithms, population norms, and cross-calibrations; and 4) psychometric evaluation. Results. Six items on pain intensity and impact satisfied requirements of unidimensionality and lack of DIF and could be scored using IRT methods. The PIQ-6 showed good internal consistency reliability (coefficient alpha = 0.94) and good construct validity. Convergent validity was supported by strong correlations with pain severity scales ( visual analog and numerical rating scales; r = 0.81–0.84); discriminant validity was suggested by correlations with the SF-8™ Health Survey Physical and Mental Component Summary measures ( r = −0.77; r = −0.32, respectively), significant mean score differences between chronic pain patients and the general population, and between patients differing in self-reported medical conditions ( P < 0.001). Conclusion. The PIQ-6 is a brief, precise questionnaire available in a paper-and-pencil version and a computerized version that includes scoring and feedback software. It may facilitate large-scale, inexpensive, precise, and norm-based pain assessment and monitoring in a wide variety of settings (e.g., homes, clinics, offices). [ABSTRACT FROM AUTHOR]

Objectives: To provide a standardized metric for the assessment of depression severity to enable comparability among results of established depression measures. Study Design and Setting: A common metric for 11 depression questionnaires was developed applying item response theory (IRT) methods. Data of 33,844 adults were used for secondary analysis including routine assessments of 23,817 in- and outpatients with mental and/or medical conditions (46% with depressive disorders) and a general population sample of 10,027 randomly selected participants from three representative German household surveys. Results: A standardized metric for depression severity was defined by 143 items, and scores were normed to a general population mean of 50 (standard deviation 5 10) for easy interpretability. It covers the entire range of depression severity assessed by established instruments. The metric allows comparisons among included measures. Large differences were found in their measurement precision and range, providing a rationale for instrument selection. Published scale-specific threshold scores of depression severity showed remarkable consistencies across different questionnaires. Conclusion: An IRT-based instrument-independent metric for depression severity enables direct comparisons among established measures. The ''common ruler'' simplifies the interpretation of depression assessment by identifying key thresholds for clinical and epidemiologic decision making and facilitates integrative psychometric research across studies, including meta-analysis. [ABSTRACT FROM AUTHOR]