Methodological aspects of the highly adaptive testing design for PISA.

This methods paper describes the methodological and statistical underpinnings of the highly adaptive testing design (HAT), which was developed for the Programme for International Student Assessment (PISA). The aim of HAT is to allow for a maximum of adaptivity in selecting items while taking the constraints of PISA into account with appropriate computer algorithms. HAT combines established methods from the area of computerized adaptive testing (a) to improve item selection when items are nested in units, (b) to make use of the correlation between the dimensions measured, (c) to efficiently accomplish constraint management, (d) to control for item position effects, and (e) to foster students' test-taking experience. The algorithm is implemented using the programming language R and readers are provided with the necessary code. This should facilitate future implementations of the HAT design and inspire other adaptive testing designs that aim to maximize adaptivity while meeting constraints.

Exploring Effects of Race and Differential Item Functioning on PrEP Stigma Experiences: Implications for Latent Stigma Measurement in Racially and Sexually Diverse Populations.

PrEP stigma measurement remains a challenge to the validity of studies and interventions addressing HIV prevention. It may lead to inaccurate assessment of the relationship between PrEP stigma and health outcomes such as PrEP persistence and care retention in groups experiencing HIV-related inequities. The present research explored the psychometric properties of a novel IV pre-exposure prophylaxis (PrEP) stigma scale in a cohort of racially diverse men who have sex with men (MSM). Using item response theory, analyses explored presence of differential item functioning (DIF) among Black and White respondents. Participants completed baseline surveys measuring psychosocial factors, sociodemographic factors, and PrEP stigma items. The primary analysis used a machine learning approach to assess (a) the presence of DIF; and (b) compare latent stigma between Black and White respondents, after correcting for any DIF. The model identified four out of 13 scale items as having a high probability of DIF for Black respondents, which is relatively good given that the original PrEP stigma scale was neither designed nor tested for validation comparing Black and White respondents. The DIF-adjusted latent PrEP stigma measure reveals statistically and substantially significantly higher levels of stigma for Black compared to White respondents (Diff.: 1.05 +/- 0.19). While most items performed well, findings demonstrate the importance of assessing measurement error in populations where stigma is rampant and being studied or intervened upon (and in this case, where multilevel and intersectional stigma may be present).

Improved Scoring of the Center for Epidemiologic Studies Depression Scale - Revised: An Item Response Theory Analysis.

The Center for Epidemiologic Studies Depression Scale - Revised (CESD-R) is a popular self-report screening measure for depression. A 20-item questionnaire with scores ranging from 0 to 4 for each item, the CESD-R can produce total scores ranging from 0 to 80. However, the typical scoring protocol for the CESD-R restricts the range of possible scores to between 0 and 60 to retain the same range and clinical cutoff scores as the original CES-D. Despite the widespread adoption of this scoring approach, the psychometric impact has never been systematically examined. In an undergraduate and community adult sample (n = 869), item response theory analyses indicated that scoring the CESD-R with all 5 response options (CESD-R5opt) provided nearly twice as much information about a person's latent depression for individuals with high levels of depression than did scoring the CESD-R with 4 response options per item (CESD-R4opt). The CESD-R5opt retained the strong reliability and factor structure of the CESD-R4opt and was more sensitive to individual differences for participants at high levels of depression compared to the CESD-R4opt. Results provide preliminary evidence that researchers and clinicians should score the CESD-R using the full 0-to-80 scale and a clinical cutoff score of 29. Supplementary Information: The online version contains supplementary material available at 10.1007/s10862-024-10155-y.

Psychometric Properties of Different Short Forms of Social Interaction Anxiety Scale in Chinese College Students.

Background: There exist four short forms of the Social Interaction Anxiety Scale (SIAS): 10-item version (SIAS-10), 6-item version by Peters et al (SIAS-6P), 6-item version by Fergus et al (SIAS-6F), and 5-item version (SIAS-5). This study aims to comprehensively examine the psychometric properties of the SIAS-10, SIAS-6P, SIAS-6F, and SIAS-5 and to determine which one performs relatively better in Chinese population. Methods: This study enrolled 733 Chinese college students. The unidimensionality of the SIAS-10, SIAS-6P, SIAS-6F, SIAS-5 was examined using Confirmatory Factor Analysis (CFA). Multi-Group CFA was further adopted to assess measurement equivalence across gender. Internal consistency reliability and criteria-related validity were also evaluated. Additionally, the measurement performance of the SIAS-10, SIAS-6P, SIAS-6F, and SIAS-5 was assessed with Item Response Theory (IRT), which estimated the discrimination parameter and the Item Characteristic Curve (ICC) for each item. Results: Except for the SIAS-5, the SIAS-10, SIAS-6P, and SIAS-6F displayed a good-fit to the one-factor model. Furthermore, the SIAS-10 achieved strict equivalence across gender while other versions did not. The SIAS-10, SIAS-6P, SIAS-6F and SIAS-5 all had acceptable internal consistency and significant correlations with criteria scales. The IRT results showed that the SIAS-10 included more items with higher discrimination and peaked ICCs (indicating more informative), whereas the SIAS-6P included more items with lower discrimination and flat ICCs (indicating less informative). Conclusion: For assessing social anxiety in Chinese under constrained conditions, the SIAS-10 is recommended to clinicians for it measuring equivalently across gender, reflecting the relevant criteria variables well, and discriminating various levels of social anxiety sensitively.

Psychometric properties of Parenting Sense of Competence Scale using item-response theory.

Parental competence is one of the essential components of raising ethical and healthy children. The mother's satisfaction with her maternal role significantly influences her cognitive responses and parenting behaviors. Having appropriate instruments to measure maternal satisfaction and identify and solve potential problems after childbirth can substantially contribute to maintaining and improving mother and infant health. This study aimed to evaluate the psychometric properties of the Parenting Sense of Competence (PSOC) Scale in mothers referring to the healthcare centers affiliated with Qazvin University of Medical Sciences. This cross-sectional psychometric study collected data from 254 mothers with 1.5-month-old infants referred to the healthcare centers in Qazvin Province. Data were analyzed using the item response theory (IRT) in SPSS 26 and Stata 17 software. The mean age (±standard deviation) of participants was 30.05 ± 5.7, and the overall Cronbach's alpha for the scale was 0.931. We used the graded response model (GRM) appropriate for Likert-type rating scales to fit the IRT. The discrimination parameter estimates showed that item 5 had a discrimination level <0.65, leading to its exclusion from the final analysis. In addition, the total information index confirmed that the scale was suitable in the trait range of -2.1 to 1.8. Compared with other common models for ordered responses based on general model fit indices, the GRM showed a better fit. The study results recommend applying the IRT models to improve and enhance the quality of questionnaires in various measurement fields.

Non-Gaussian Liability Distribution for Depression in the General Population.

Unlike depression sum scores, the underlying risk for depression is typically assumed to be normally distributed across the general population. To assess the true empirical shape of depression risk, we created a continuous-valued estimate of the latent depression density, using the Davidian-Curve Item Response Theory (DC-IRT) and the National Health and Nutrition Examination Survey (NHANES) cohorts from 2005 to 2018 (n = 36,244 on the Nine-item Patient Health Questionnaire; PHQ-9). We conducted simulations to investigate the performance of DC-IRT for large samples and realistic items. The method can recover complex latent-risk distributions even when they are not evident from sum scores. However, estimation accuracy for different sample sizes depends on the method of model selection. In addition to full-data analysis, random samples of a few thousand observations were drawn for analysis. The latent shape of depression was left-skewed and bimodal in both investigations, indicating that the latent-normality assumption does not hold for depression.

Pre-natal and early life lead exposure and childhood inhibitory control: an item response theory approach to improve measurement precision of inhibitory control.

BACKGROUND: Neurodevelopmental performance tasks are often separately analyzed, even when they tap into a similar construct. This may yield mixed findings for associations of an exposure-neurobehavioral outcome. We develop an item response theory (IRT) approach to integrate multiple task variables together to improve measurement precision of the underlying construct. We apply this approach to create an integrative measure of childhood inhibitory control, and study impacts of pre/post-natal lead exposure. METHODS: Using data from a prospective cohort based in Mexico (N = 533), we created an inhibitory control scale that integrates accuracy and reaction time information from four inhibitory control tasks (Go/NoGo Letter, Go/NoGo Neutral, Go/NoGo Happy, Delis-Kaplan Executive Function System (D-KEFS) Color-Word Interference Test, Condition 3). Using a generalized partial credit item response theory model, we estimated an inhibitory control index for each participant. We then assessed adjusted associations between umbilical cord blood and 4-year lead and childhood inhibitory control. We developed a resampling approach to incorporate error estimates from the inhibitory control variable to confirm the consistency of the lead-inhibitory control associations. We modeled time-varying associations of lead with each inhibitory control measure separately. RESULTS: Participants had a median age of 9 years; 51.4% were males. Umbilical cord blood [-0.06 (95% CI: -0.11, -0.01)] and 4-year lead [-0.07 (95% CI: -0.12, -0.02)] were associated with inhibitory control index at 8-10 years. A resampling approach confirmed that 4-year lead was consistently associated with childhood inhibitory control index. Umbilical cord blood and 4-year lead were each associated with 3 out of 8 measures in separate models. CONCLUSION: This is the first application of IRT in environmental epidemiology to create a latent variable for inhibitory control that integrates accuracy and reaction time information from multiple, related tasks. This framework can be applied to other correlated neurobehavioral assessments or other phenotype data.

Psychometric properties of computerized adaptive testing for chronic obstructive pulmonary disease patient-reported outcome measurement.

BACKGROUND: Computerized adaptive testing (CAT) is an effective way to reduce time, repetitious redundancy, and respond burden, and has been used to measure outcomes in many diseases. This study aimed to develop and validate a comprehensive disease-specific CAT for chronic obstructive pulmonary disease (COPD) patient-reported outcome measurement. METHODS: The discrimination and difficulty of the items from the modified patient-reported outcome scale for COPD (mCOPD-PRO) were analyzed using item response theory. Then the initial item, item selection method, ability estimation method, and stopping criteria were further set based on Concerto platform to form the CAT. Finally, the reliability and validity were validated. RESULTS: The item discrimination ranged from 1.05 to 2.71, and the item difficulty ranged from - 3.08 to 3.65. The measurement reliability of the CAT ranged from 0.910 to 0.922 using random method, while that ranged from 0.910 to 0.924 using maximum Fisher information (MFI) method. The content validity was good. The correlation coefficient between theta of the CAT and COPD assessment test and modified Medical Research Council dyspnea scale scores using random method was 0.628 and 0.540 (P < 0.001; P < 0.001) respectively, while that using MFI method was 0.347 and 0.328 (P = 0.007; P = 0.010) respectively. About 11 items (reducing by 59.3%) on average were tested using random method, while about seven items (reducing by 74.1%) on average using MFI method. The correlation coefficient between theta of the CAT and mCOPD-PRO total scores using random method was 0.919 (P < 0.001), while that using MFI method was 0.760 (P < 0.001). CONCLUSIONS: The comprehensive disease-specific CAT for COPD patient-reported outcome measurement is well developed with good psychometric properties, which can provide an efficient, accurate, and user-friendly measurement for patient-reported outcome of COPD.

A Review of Some of the History of Factorial Invariance and Differential Item Functioning.

The concept of factorial invariance has evolved since it originated in the 1930s as a criterion for the usefulness of the multiple factor model; it has become a form of analysis supporting the validity of inferences about group differences on underlying latent variables. The analysis of differential item functioning (DIF) arose in the literature of item response theory (IRT), where its original purpose was the detection and removal of test items that are differentially difficult for, or biased against, one subpopulation or another. The two traditions merge at the level of the underlying latent variable model, but their separate origins and different purposes have led them to differ in details of terminology and procedure. This review traces some aspects of the histories of the two traditions, ultimately drawing some conclusions about how analysts may draw on elements of both, and how the nature of the research question determines the procedures used. Whether statistical tests are grouped by parameter (as in studies of factorial invariance) or across parameters by variable (as in DIF analysis) depends on the context and is independent of the model, as are subtle aspects of the order of the tests. In any case in which DIF or partial invariance is a possibility, the invariant parameters, or anchor items in DIF analysis, are best selected in an interplay between the statistics and judgment about what is being measured.

Item response theory for before-after designs in interprofessional education research.

Although Item Response Theory (IRT) has been recommended for helping advance interprofessional education (IPE) research, its use remains limited. This may be partly explained by potential misconceptions regarding IRT`s "limitation" to cross-sectional data. The aim of this study is to demonstrate how Item Response Theory (IRT) can be applied effectively in before-and-after designs in IPE research. Specifically, a two-week before-after design with survey methodology using the Extended Professional Identity Scale (EPIS), an interprofessional identity measure, was conducted among n = 146 mixed health-science students. Results indicated that EPIS increased significantly before-after intervention by .74 standardised mean differences, t146 = 7.73, p < .05. The before-after IRT model also gave a test-retest reliability estimate of .60 which was considered acceptable. Comparison of the IRT model with a conventional paired-t-test indicated similar effect size estimates of Cohen's d = .56 and .54, respectively. We demonstrate IRT`s flexibility to before-after studies in IPE. Application of this model can yield accurate changes in target IPE constructs, and it is advantageous to classical test theory vis-à-vis baseline differences.

An Item Response Theory Analysis of the Psychosis Screening Questionnaire in Ethiopia.

AIM: Few psychosis screening instruments have been tested for use in Africa, yet appropriate tools can increase the detection of self-reported psychotic symptoms, improve the detection of psychosis and impact its prognosis. METHOD: The construct validity and factor structure of Psychosis Screening Questionnaire (PSQ) were tested with confirmatory factor analysis (CFA) and item response theory (IRT) in a sample of 1928 Ethiopian adults without any history of psychosis. We tested a unidimensional model with and without an item on mania. For IRT, unidimensional latent structure one-parameter logistic (1PL) and two-parameter (2PL) logistic models were tested and compared for relative fit using a likelihood-ratio test. RESULT AND DISCUSSION: The prevalence of lifetime positive screens was 2.8% in an Ethiopian sample of adults from a general medical setting. A unidimensional model demonstrated good fit for the PSQ, (CFI = 0.993, TLI = 0.986 and RMSEA = 0.025). For IRT, a 2PL model was the best fitting one. IRT tests of item difficulty and discrimination parameters showed that paranoia had the highest discrimination α = 4.59 $$ \left(\alpha =4.59\right) $$ and lowest difficulty ( ß = 2.53 $$ \beta =2.53 $$ ), likely to be endorsed at low levels of psychotic features. Thought insertion had the highest item difficulty ( ß = 2.98 $$ \beta =2.98 $$ ). Overall, the measure captures the psychosis construct at higher levels of the latent trait and may be suited for detecting moderate to severe levels of psychosis. CONCLUSION: The PSQ is found to have good construct validity in screening for psychosis among Ethiopian adults. Future studies may focus on the diagnostic validity of the PSQ comparing it with a structured clinical interview.

Chinese version of the Death Anxiety Beliefs and Behaviours Scale: Psychometric properties based on CTT and IRT.

OBJECTIVES: The Death Anxiety Beliefs and Behaviour Scale (DABBS) is a unique tool designed to assess the detrimental beliefs and avoidant behaviors linked to death anxiety. This study aimed to adapt the DABBS into Chinese and verify its psychometric characteristics within a community-dwelling older adult population. METHODS: This study used a cross-sectional design and translated the DABBS into Chinese. The psychometric properties of 437 community-dwelling older persons were assessed using the Classical Test Theory (CTT) and Item Response Theory (IRT). RESULTS: The DABBS consisted of affect, beliefs, and behaviours, with 18 entries in 3 dimensions. The I-CVI of the DABBS ranged from 0.857 to 1.000, and the S-CVI was 0.968; Cronbach's alpha of 0.905. Rasch analysis results showed that the 3 dimensions of the scale possessed good unidimensionality, and the entries were well-fitted to the dimensions in which they were located; each entry Infit MNSQ and Outfit MNSQ were in the range of 0.50 to 1.50; the analysis of the functional differences of items in different characteristic subgroups (gender) showed that the absolute value of DIF Contrast was <0.50. The results of the Wright map showed that the ability of the participants was normally distributed, and the difficulty of the scale's entries was adapted to the average ability level of older adults. CONCLUSIONS: The present data indicate that the revised DABBS is a valid and reliable tool for assessing affect, beliefs, and behaviors associated with death anxiety in community-dwelling older individuals.

Item response theory analysis of the Chinese version compulsive shopping scale.

Compulsive shopping, a behavioral disorder with significant personal and social repercussions, necessitates reliable assessment tools, especially within different cultural contexts. While several scales exist to measure compulsive buying behavior, there is a lack of validated instruments tailored to the Chinese population. This study aimed to examine the psychometric properties of the Chinese version of the Compulsive Shopping Scale (CSS) using Item Response Theory (IRT). A total of 637 young healthy participants (42.5 % males and 57.5 % females), with a mean age of 21.32 years (SD = 2.06), both undergraduate and postgraduate students, were recruited from various cities in China. Sixty-four participants were retested after a two-week interval to assess test-retest reliability. The results indicated that a one-dimensional factor structure was appropriate. The reliability analyses, including test-retest reliability, ω, α, and λ6 tests, demonstrated good internal consistency. The rating scale model analysis showed infit and outfit MNSQ values between 0.6 and 1.4, indicating a good fit. The item information curve and test information curve indicated a normal distribution of scores. Differential item functioning was observed in two items, suggesting potential gender-related differences. These findings indicate that the Chinese version of the CSS is a reliable and valid instrument for measuring compulsive shopping behaviors in Chinese populations.

Large-Scale Item-Level Analysis of the Figural Matrices Test in the Norwegian Armed Forces: Examining Measurement Precision and Sex Bias.

Figural matrices tests are common in intelligence research and have been used to draw conclusions regarding secular changes in intelligence. However, their measurement properties have seldom been evaluated with large samples that include both sexes. Using data from the Norwegian Armed Forces, we study the measurement properties of a test used for selection in military recruitment. Item-level data were available from 113,671 Norwegian adolescents (32% female) tested between the years 2011 and 2017. Utilizing item response theory (IRT), we characterize the measurement properties of the test in terms of difficulty, discrimination, precision, and measurement invariance between males and females. We estimate sex differences in the mean and variance of the latent variable and evaluate the impact of violations to measurement invariance on the estimated distribution parameters. The results show that unidimensional IRT models fit well in all groups and years. There is little difference in precision and test difficulty between males and females, with precision that is generally poor on the upper part of the scale. In the sample, male latent proficiency is estimated to be slightly higher on average, with higher variance. Adjusting for measurement invariance generally reduces the sex differences but does not eliminate them. We conclude that previous studies using the Norwegian GMA data must be interpreted with more caution but that the test should measure males and females equally fairly.

A Follow up on the Continuum Theory of Eco-Anxiety: Analysis of the Climate Change Anxiety Scale Using Item Response Theory among French Speaking Population.

The mental health impact of the environmental crisis, particularly eco-anxiety, is a growing research topic whose measurement still lacks consensus. This study aims to use item response theory (IRT) to gain a deeper understanding of the constructs measured by existing questionnaires. To conduct this review, we applied the graded response model with the help of the MIRT package in R on open-access data from the short French version of the Climate Change Anxiety Questionnaire, which measures cognitive-emotional impairment and functional impairment. The models tested in this study are the one, two, and three-factor models, and the bifactor model. After model selection, the psychometric properties of the selected model were tested. Our results suggest that the unidimensional model seems to be the most appropriate for measuring eco-anxiety. The item difficulty parameter extracted from the IRT enabled us to discuss the severity levels of the items comprising this tool. The Climate Change Anxiety Questionnaire appears to be more appropriate for measuring moderate to severe eco-anxiety. Avenues for improving this questionnaire and the measurement of eco-anxiety in general are then discussed.

A longitudinal examination of the psychometric properties of the English perceived stress scale- four (PSS-4) in mental health counsellors using item response theory.

We examined the longitudinal psychometric properties of the Perceived Stress Scale - 4 items version (PSS-4) using item response theory with a sample of 361 mental health counsellors. Participants completed the PSS-4 at three timepoints at six-month intervals in a one-year period. There were 290 participants who (80.3%) identified as female, 51 (14.1%) identified as male, eight (2.2%) identified as gender variant/non-conforming, seven (1.9%) wrote in their own gender identity (e.g., genderqueer, gender expansive), three (0.8%) identified as Transgender male, and two (0.6%) did not respond to the item. The racial and ethnic backgrounds were as follows: White (87.3%), Multiracial (5.5%), Latino or Hispanic or Spanish (2.8%), Black or African American (1.4%), Asian (0.8%), Middle Eastern (0.8%), and five did not respond to the item (1.4%). We found unidimensionality evidence of the PSS-4 across all three timepoints and response categories were monotonically ordered. We also found that across all timepoints, the average person location was lower than the average item location, suggesting that the PSS-4 may not be well-targeted for this sample of mental health counsellors. We observed no significant interactions between timepoints, hours worked per week, and length of employment. Implications of the findings, including a discussion of the utility of the PSS-4 as a global measure of stress and with mental health counsellors.

Item response theory validation of the Oxford knee score and Activity and Participation Questionnaire: a step toward a common metric.

OBJECTIVES: The Oxford knee score (OKS) and OKS Activity and Participation Questionnaire (OKS-APQ) are patient-reported outcome measures used to assess people undergoing knee replacement surgery. They have not explicitly been tested for unidimensionality (whether they measure one underlying trait such as 'knee health'). This study applied item response theory (IRT) to improve the validity of the instruments to optimize for ongoing use. STUDY DESIGN AND SETTING: Participants undergoing primary total knee replacement (TKR) provided preoperative and postoperative responses for OKS and OKS-APQ. Confirmatory factor analysis (CFA) were performed on the OKS and OKS-APQ separately and then on both when pooled into one. An IRT model was fitted to the data. RESULTS: 2972 individual response patterns were analyzed. CFA demonstrated that when combining OKS and OKS-APQ as one instrument, they measure one latent health trait. A user-friendly, free-to-use, web app has been developed to allow clinicians to upload raw data and instantly receive IRT scores. CONCLUSIONS: The OKS and OKS-APQ can be combined to use effectively as a single instrument (producing a single score). For the separate OKS and OKS-APQ the original items and response options can continue to be posed to patients, and this study has confirmed the suitability of IRT-weighted scoring. Applying IRT to existing responses converts traditional sum scores into continuous measurements with greater granularity, including individual measurement error.

Cross-cultural adaptation of the awareness and beliefs about cancer measure for Hispanics/Latinos living in the United States.

Introduction: The purpose of this study is to culturally adapt the Awareness and Beliefs about Cancer (ABC) measure for use in the Hispanic/Latino population living in the United States (US). Methods: In accordance with Patient Reported Outcomes (PRO) Consortium guidelines for cross-cultural adaptation of measures for content and linguistic validity, we conducted: two forward-translations, reconciliation, two back-translations, revision and harmonization, six cognitive interviews, revision, external expert review, and finalization of the version. We used a mixed methods approach, conducting cognitive interviews with Hispanic/Latino community members while also convening an expert panel of six clinicians, health professionals, and community representatives and including the in the entire process. After cross-culturally adapting the ABC measure, we assessed the psychometric properties of the instrument using item response theory analysis. Item parameters, discrimination and category thresholds, and standard errors were calculated. For each of the adapted subdomains, we used item information curves to report the graphical profile of item effectiveness. Results: Twenty-two Hispanic/Latino community members were enrolled in cognitive interviews, and Hispanics/Latinos fluent in Spanish completed the measure to assess its psychometric properties. Cognitive interviews revealed opportunities to improve items. Key changes from the original measure include the inclusion of gender inclusive language and an inquiry into e-cigarette use on items related to smoking habits. Psychometric property analyses revealed that the anticipated delay in seeking medical help, general cancer beliefs, and cancer screening beliefs and behaviors subdomains had some slope parameters that were < 1; this implies that those items were not able to adequately discriminate the latent trait and had poor performance. Discussion: The adapted ABC measure for US Hispanics/Latinos meets content and linguistic validity standards, with construct validity confirmed for cancer symptom recognition and barriers to symptomatic presentation subdomains, but revisions are necessary for others, highlighting the need for ongoing refinement to ensure the cultural appropriateness of instruments.

Investigating Heterogeneity in Response Strategies: A Mixture Multidimensional IRTree Approach.

To improve the validity of self-report measures, researchers should control for response style (RS) effects, which can be achieved with IRTree models. A traditional IRTree model considers a response as a combination of distinct decision-making processes, where the substantive trait affects the decision on response direction, while decisions about choosing the middle category or extreme categories are largely determined by midpoint RS (MRS) and extreme RS (ERS). One limitation of traditional IRTree models is the assumption that all respondents utilize the same set of RS in their response strategies, whereas it can be assumed that the nature and the strength of RS effects can differ between individuals. To address this limitation, we propose a mixture multidimensional IRTree (MM-IRTree) model that detects heterogeneity in response strategies. The MM-IRTree model comprises four latent classes of respondents, each associated with a different set of RS traits in addition to the substantive trait. More specifically, the class-specific response strategies involve (1) only ERS in the "ERS only" class, (2) only MRS in the "MRS only" class, (3) both ERS and MRS in the "2RS" class, and (4) neither ERS nor MRS in the "0RS" class. In a simulation study, we showed that the MM-IRTree model performed well in recovering model parameters and class memberships, whereas the traditional IRTree approach showed poor performance if the population includes a mixture of response strategies. In an application to empirical data, the MM-IRTree model revealed distinct classes with noticeable class sizes, suggesting that respondents indeed utilize different response strategies.

How well can we measure chronic pain impact in existing longitudinal cohort studies? Lessons learned.

Multiple large longitudinal cohorts provide opportunities to address questions about predictors of pain and pain trajectories, even when not anticipated in design of the historical databases. This focus article uses two empirical examples to illustrate the processes of assessing the measurement properties of data from large cohort studies to answer questions about pain. In both examples, data were screened to select candidate variables that captured the impact of chronic pain on self-care activities, productivity and social activities. We describe a series of steps to select candidate items and evaluate their psychometric characteristics in relation to the measurement of pain impact proposed. In UK Biobank, a general lack of internal consistency of variables selected prevented the identification of a satisfactory measurement model, with lessons for the measurement of chronic pain impact. In the English Longitudinal Study of Ageing, a measurement model for chronic pain impact was identified, albeit limited to capturing the impact of pain on self-care and productivity but lacking coverage related to social participation. In conjunction with its supplementary material, this focus article aims to encourage exploration of these valuable prospectively collected data; to support researchers to make explicit the relationships between items in the databases and constructs of interest in pain research; and to use empirical methods to estimate the possible biases in these variables. PERSPECTIVE: This focus article outlines a theory-driven approach for fitting new measurement models to data from large cohort studies, and evaluating their psychometric properties. This aims to help researchers develop an empirical understanding of the gains and limitations connected with the process of re-purposing the data stored in these datasets.