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Purpose: Thresholds for meaningful within-individual change (MWIC) are useful for interpreting patient-reported outcome measures (PROM). Transition ratings (TR) have been recommended as anchors to establish MWIC. Traditional statistical methods for analyzing MWIC such as mean change analysis, receiver operating characteristic (ROC) analysis, and predictive modeling ignore problems of floor/ceiling effects and measurement error in the PROM scores and the TR item. We present a novel approach to MWIC estimation for multi-item scales using longitudinal item response theory (LIRT)., Methods: A Graded Response LIRT model for baseline and follow-up PROM data was expanded to include a TR item measuring latent change. The LIRT threshold parameter for the TR established the MWIC threshold on the latent metric, from which the observed PROM score MWIC threshold was estimated. We compared the LIRT approach and traditional methods using an example data set with baseline and three follow-up assessments differing by magnitude of score improvement, variance of score improvement, and baseline-follow-up score correlation., Results: The LIRT model provided good fit to the data. LIRT estimates of observed PROM MWIC varied between 3 and 4 points score improvement. In contrast, results from traditional methods varied from 2 to 10 points-strongly associated with proportion of self-rated improvement. Best agreement between methods was seen when approximately 50% rated their health as improved., Conclusion: Results from traditional analyses of anchor-based MWIC are impacted by study conditions. LIRT constitutes a promising and more robust analytic approach to identifying thresholds for MWIC., (© 2022. The Author(s).)

Purpose: ReQoL-10 and ReQoL-20 have been developed for use as outcome measures with individuals aged 16 and over, experiencing mental health difficulties. This paper reports modelling results from the item response theory (IRT) analyses that were used for item reduction., Methods: From several stages of preparatory work including focus groups and a previous psychometric survey, a pool of items was developed. After confirming that the ReQoL item pool was sufficiently unidimensional for scoring, IRT model parameters were estimated using Samejima's Graded Response Model (GRM). All 39 mental health items were evaluated with respect to item fit and differential item function regarding age, gender, ethnicity, and diagnosis. Scales were evaluated regarding overall measurement precision and known-groups validity (by care setting type and self-rating of overall mental health)., Results: The study recruited 4266 participants with a wide range of mental health diagnoses from multiple settings. The IRT parameters demonstrated excellent coverage of the latent construct with the centres of item information functions ranging from - 0.98 to 0.21 and with discrimination slope parameters from 1.4 to 3.6. We identified only two poorly fitting items and no evidence of differential item functioning of concern. Scales showed excellent measurement precision and known-groups validity., Conclusion: The results from the IRT analyses confirm the robust structure properties and internal construct validity of the ReQoL instruments. The strong psychometric evidence generated guided item selection for the final versions of the ReQoL measures.

Purpose: Tardive dyskinesia (TD) is a common but serious hyperkinetic movement disorder and side effect of antipsychotic medications used to treat bipolar disorder (BD), major depressive disorder (MDD), and schizophrenia (SZ). The purpose of this study was to evaluate health-related quality of life (HRQoL) in a population with diagnoses for BD, MDD, or SZ by comparing patients with TD (n = 197) with those without TD (n = 219). HRQoL in each group was also compared with HRQoL of the general population., Methods: This study employed a cross-sectional web-based survey. HRQoL was assessed by four instruments: the SF-12 Health Survey, Version 2 (SF-12v2), the Quality of Life Enjoyment and Satisfaction Questionnaire, Short Form (Q-LES-Q-SF), the Social Withdrawal subscale of the Internalized Stigma of Mental Illness Scale (SW-ISMI); and two questions on movement disorders., Results: Patients with TD had significantly worse HRQoL and social withdrawal than those without. The differences were more pronounced for physical HRQoL domains than for mental health domains. Patients with more-severe TD, assessed through either self-rating or clinician rating, experienced significantly worse HRQoL than did those with less-severe TD. The impact of TD was substantially greater in patients with SZ than in those with BD or MDD. Compared with the general population, patients with BD, MDD, or SZ experienced significantly worse HRQoL regardless of TD status, although this deficit in HRQoL was greater among those with TD., Conclusions: The presence of TD is associated with worse HRQoL and social withdrawal. The most severe impact of TD is on physical aspects of patients' HRQoL.

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.

Purpose: The objective of this study was to estimate the association between SF-12v2® Health Survey (SF-12v2) scores and subsequent health care resource utilization (HCRU) among patients with cancer., Methods: We analyzed 18+ year participants in the Medical Expenditure Panel Survey, diagnosed with active cancer or malignancy (n = 647). HCRU was measured by total medical expenditures (MEs) and number of medical events (EVs) in the 6 months following the SF-12v2 assessment. The effect of SF-12v2 scores (physical (PCS) and mental (MCS) component summary scores and the SF-6D health-utility score) on HCRU was estimated using generalized linear models. Estimates were obtained for the entire sample and for the four cancer groups present in the sample: breast, prostate, skin, and lung., Results: For PCS and MCS, a one-point better score was associated with 2% lower MEs (P < 0.001) and 2.5% lower MEs (P = 0.015), respectively. A 0.05-point better SF-6D score was associated with 7% lower MEs (P = 0.003). PCS and SF-6D were more strongly associated with MEs for prostate cancer patients (P = 0.009 and P = 0.003) and PCS was more strongly associated with MEs for skin cancer patients (P = 0.019), compared to other cancer groups. A 1-point better PCS predicted 1% lower EVs, while a 0.05 better SF-6D score predicted 4% lower EVs., Conclusions: The significant associations between SF-12v2 scores from oncology patients and subsequent HCRU can guide interpretations of SF-12v2 scores in evaluation of therapies and in health policy decisions.

Purpose: The purpose of this study was to adapt different domains of an existing retrospective questionnaire to momentary versions, to use and assess cognitive interviewing for evaluating the new versions, and to compare momentary compatibility (i.e. an item's potential to be validly converted to a momentary version) across different scales., Methods: Initial momentary versions of retrospective patient-reported outcomes were produced by converting present perfect tense wording to present tense wording. Cognitive interviews were conducted iteratively with 21 patients to determine which reference period they actually employed, and to identify problems with new, revised versions. A think-aloud interview protocol was supplemented with non-specific concurrent and specific retrospective probing. The momentary compatibility of each item was evaluated by calculating the proportion of interviews wherein momentary reference periods were identified; problems were categorized according to cognitive aspects of survey methodology taxonomy. The efficiency of various cognitive interviewing techniques was determined by evaluating whether applied reference periods were identified by think-aloud alone or by supplementary probes., Results: The momentary compatibility varied from 5 to 100% across items. Cognitive interviews revealed potential problems of various severities in the majority of items. Think-aloud alone was sufficient at determining the applied reference period in one-third of the cases, and the efficiency of additional concurrent and retrospective probing was 50 and 94%, respectively., Conclusions: Cognitive interviewing techniques proved useful for developing and evaluating momentary items. Researchers should be aware of the applied reference period and of emerging problems when evaluating adapted momentary items, since not all concepts are suitable. We recommend the proposed method in future adaptations of existing instruments.

Purpose: We aimed to identify the best approach to work ability assessment in patients with thyroid disease by evaluating the factor structure, measurement equivalence, known-groups validity, and predictive validity of a broad set of work ability items., Methods: Based on the literature and interviews with thyroid patients, 24 work ability items were selected from previous questionnaires, revised, or developed anew. Items were tested among 632 patients with thyroid disease (non-toxic goiter, toxic nodular goiter, Graves' disease (with or without orbitopathy), autoimmune hypothyroidism, and other thyroid diseases), 391 of which had participated in a study 5 years previously. Responses to select items were compared to general population data. We used confirmatory factor analyses for categorical data, logistic regression analyses and tests of differential item function, and head-to-head comparisons of relative validity in distinguishing known groups., Results: Although all work ability items loaded on a common factor, the optimal factor solution included five factors: role physical, role emotional, thyroid-specific limitations, work limitations (without disease attribution), and work performance. The scale on thyroid-specific limitations showed the most power in distinguishing clinical groups and time since diagnosis. A global single item proved useful for comparisons with the general population, and a thyroid-specific item predicted labor market exclusion within the next 5 years (OR 5.0, 95 % CI 2.7-9.1)., Conclusions: Items on work limitations with attribution to thyroid disease were most effective in detecting impact on work ability and showed good predictive validity. Generic work ability items remain useful for general population comparisons.

Background and Purpose: Thyroid diseases are common and often affect quality of life (QoL). No cross-culturally validated patient-reported outcome measuring thyroid-related QoL is available. The purpose of the present study was to test the cross-cultural validity of the newly developed thyroid-related patient-reported outcome ThyPRO, using tests for differential item functioning (DIF) according to language version., Methods: The ThyPRO consists of 85 items summarized in 13 multi-item scales and one single item. Scales cover physical and mental symptoms, well-being and function as well as social and daily function and cosmetic concerns. Translation applied standard forward-backward methodology with subsequent cognitive interviews and reviews. Responses (N = 1,810) to the ThyPRO were collected in seven countries: UK (n = 166), The Netherlands (n = 147), Serbia (n = 150), Italy (n = 110), India (n = 148), Denmark (n = 902) and Sweden (n = 187). Translated versions were compared pairwise to the English version by examining uniform and nonuniform DIF, i.e., whether patients from different countries respond differently to a particular item, although they have identical level of the concept measured by the item. Analyses were controlled for thyroid diagnosis. DIF was investigated by ordinal logistic regression, testing for both statistical significance and magnitude (ΔR (2) > 0.02). Scale level was estimated by the sum score, after purification., Results: For twelve of the 84 tested items, DIF was identified in more than one language. Eight of these were small, but four were indicative of possible low translatability. Twenty-one instances of DIF in single languages were identified, indicating potential problems with the particular translation. However, only seven were of a magnitude which could affect scale scores, most of which could be explained by sample differences not controlled for., Conclusion: The ThyPRO has good cross-cultural validity with only minor cross-cultural invariance and is recommended for use in international multicenter studies.

Objective: To evaluate the extent of differential item functioning (DIF) within the thyroid-specific quality of life patient-reported outcome measure, ThyPRO, according to sex, age, education and thyroid diagnosis., Study Design and Setting: A total of 838 patients with benign thyroid diseases completed the ThyPRO questionnaire (84 five-point items, 13 scales). Uniform and nonuniform DIF were investigated using ordinal logistic regression, testing for both statistical significance and magnitude (∆R(2) > 0.02). Scale level was estimated by the sum score, after purification., Results: Twenty instances of DIF in 17 of the 84 items were found. Eight according to diagnosis, where the goiter scale was the one most affected, possibly due to differing perceptions in patients with auto-immune thyroid diseases compared to patients with simple goiter. Eight DIFs according to age were found, of which 5 were in positively worded items, which younger patients were more likely to endorse; one according to gender: women were more likely to report crying, and three according to educational level. The vast majority of DIF had only minor influence on the scale scores (0.1-2.3 points on the 0-100 scales), but two DIF corresponded to a difference of 4.6 and 9.8, respectively., Conclusion: Ordinal logistic regression identified DIF in 17 of 84 items. The potential impact of this on the present scales was low, but items displaying DIF could be avoided when developing abbreviated scales, where the potential impact of DIF (due to fewer items) will be larger.