Nonuniform Differential Item Functioning Research Articles

The Use of Multidimensional Item Response Theory Estimations in Controlling Differential Item Functioning

ABSTRACT Differential Item Functioning (DIF), which indicates differences in item performance between individuals of equivalent ability in different groups, is the focus of this study. The aim was to investigate the effectiveness of Multidimensional Item Response Theory (MIRT) ability estimation in controlling DIF under different simulation conditions. For the purpose of the study, different experimental conditions were created by varying the number of dimensions, DIF percentage, DIF size and DIF type. Depending on the changed conditions, Item Response Theory and MIRT estimations were performed; the significance of the differences in Type I error and power ratios obtained from the DIF analysis of the data sets obtained from the estimations were tested with Factorial ANOVA. This study shows that in tests with DIF, taking into account the ability level related to the structure by estimating with MIRT provides a correction in the ability estimation and controls the DIF effect. In the Uniform DIF type, Type 1 error increases as the DIF size and percentage increase, and multidimensional estimation provides more correction on power ratios as the DIF size and number of dimensions increase. Whereas in the non-uniform DIF type, Type 1 error increases as DIF size increases; multidimensional estimation provides more correction on power ratios as DIF size, DIF percentage and number of dimensions increase. In this context, it is recommended that practitioners should perform MIRT estimation in the presence of DIF and conduct DIF investigations based on the corrected ability estimation taking into account the ability scores related to the structure.

Validation of the Barthel Index in Chinese nursing home residents: an item response theory analysis.

The Barthel Index (BI) is used to standardize the grading of assessments for clinical needs, insurance support, and long-term care resource allocation in China. However, its psychometric properties among nursing home residents remain unclear. Therefore, this study aims to assess and modify the psychometric properties of BI in nursing home residents. A total of 1,402 individuals undergoing evaluation in a nursing home facility in China were included in this study from November 2021 to November 2022. Correlations between items were examined to identify the potential multicollinearity concerns. The unidimensional item response theory (IRT) was used to validate and modify the single structure of BI. Furthermore, the logistic regression/IRT hybrid DIF detection method was conducted to assess differential item functioning (DIF) between the dementia group and the normal group. The pairing of items 5 ("bowl control") and 6 ("bladder control") revealed a local dependence issue, leading to their consolidation. Items 56 (bowel and bladder control) and 9 (mobility) both displayed poor fit indices and underwent category collapsing. Through the application of the generalized partial credit model, the adjusted scale displayed better fit indices, demonstrating a robust discriminative power (DC >1.5) and orderly thresholds. Furthermore, non-uniform DIF was identified in item 2 (bathing) between the dementia group and the normal group. The modified BI demonstrated favorable psychometric properties and proved to be suitable for evaluating nursing home residents experiencing moderate functional impairment, which may provide a precise evaluation for long-term care resource allocation. Future studies could explore integrating supplementary measurements, such as objective indices, to assess a broader spectrum of functional statuses to potentially enhance the limited precision width observed in BI.

A cross-cultural study of differential item functioning analysis of beliefs about Language Learning Inventory (BALLI)

This research examines students' beliefs about language learning by evaluating the measurement equivalence of the beliefs about Language Learning Inventory (BALLI). The graded response model (GRM) was used to examine differential item functioning (DIF) in the BALLI across four different countries, namely: Iran, Malaysia, Indonesia, and Bangladesh. The sample was drawn from 1613, including 500 males and 1113 females who completed the online version of the BALLI, comprising five subscales of beliefs about foreign language aptitude, the difficulty of language learning, the nature of language learning, learning and communication strategies, and motivations and expectations. Most BALLI items showed non-uniform DIF. This finding implies that students in different countries had different perceptions of the BALLI items. Therefore, researchers should be very cautious about using the BALLI in different countries. This cross-cultural comparison may generate new insights into revising the BALLI items or developing another scale to compare students' beliefs about language learning in different countries.

Understanding the alternative Mantel-Haenszel statistic: Factors affecting its robustness to detect non-uniform DIF

Test-item bias has become an increasingly challenging issue in statistics and education. A popular method, the Mantel-Haenszel test, is used for detecting non-uniform differential item functioning (DIF) but requires constructing several performance tiers to maintain robustness. The alternative Mantel-Haenszel (AMH) test was developed within the last three decades as a proxy procedure requiring only two scoring tiers. However, there needs to be more information on how essential factors like comparison group sizes and question discrimination affect its ability to detect bias. This study investigates how item difficulty and discrimination and the examined ratio between the focal and reference groups impact the likelihood of the AMH test detecting DIF. A comprehensive simulation study was conducted where the test scores were generated under three conditions. There are three commonly used difficulty levels (easy, medium, and hard), two discrimination levels (referred to as 'low’ and 'high’), and three group comparison ratios (1:1, 2:1, and 5:1). The simulation study showed the AMH test’s detection rates comparable to those of other standardized procedures like the Breslow-Day (BD) and even better. The current study aims to investigate and determine the factors that affect AMH test detection behavior. The study concludes with an application involving collegiate-level test data comparing students across genders and majors.

Examining Differential Item Functioning from a Multidimensional IRT Perspective.

Differential item functioning (DIF) is a standard analysis for every testing company. Research has demonstrated that DIF can result when test items measure different ability composites, and the groups being examined for DIF exhibit distinct underlying ability distributions on those composite abilities. In this article, we examine DIF from a two-dimensional multidimensional item response theory (MIRT) perspective. We begin by delving into the compensatory MIRT model, illustrating and how items and the composites they measure can be graphically represented. Additionally, we discuss how estimated item parameters can vary based on the underlying latent ability distributions of the examinees. Analytical research highlighting the consequences of ignoring dimensionally and applying unidimensional IRT models, where the two-dimensional latent space is mapped onto a unidimensional, is reviewed. Next, we investigate three different approaches to understanding DIF from a MIRT standpoint: 1. Analytically Uniform and Nonuniform DIF: When two groups of interest have different two-dimensional ability distributions, a unidimensional model is estimated. 2. Accounting for complete latent ability space: We emphasize the importance of considering the entire latent ability space when using DIF conditional approaches, which leads to the mitigation of DIF effects. 3. Scenario-Based DIF: Even when underlying two-dimensional distributions are identical for two groups, differing problem-solving approaches can still lead to DIF. Modern software programs facilitate routine DIF procedures for comparing response data from two identified groups of interest. The real challenge is to identify why DIF could occur with flagged items. Thus, as a closing challenge, we present four items (Appendix A) from a standardized test and invite readers to identify which group was favored by a DIF analysis.

사교육 참여가 수학 정의적 태도에 미치는 영향

This study examined the direct effect of math private education participation on the indicators of math affective attitudes, and analyzed the effect of private education participation on the latent class membership of math affective attitudes. To this end, the survey data of first-year middle school students in the 2015 Gyeonggi Education Panel Study(GEPS) were applied to the latent class MIMIC model. As a result, heterogeneous latent classes for math affective attitudes were detected, and uniform and non-uniform differential item functioning were detected depending on whether math private education participated. In addition, the significant impact of participation in math private education on latent class membership was confirmed. This study confirmed the necessity of measurement invariance by analyzing the effect of math private education on individual items of math affective attitudes, and verified the effect of participation in private education on the latent class of math affective attitudes, it presents meaningful implications for math education in the school field.

30 Item response theory and differential item functioning of the AD8: The High School & Beyond Study

Objective:The AD8 is a validated screening instrument for functional changes that may be caused by cognitive decline and dementia. It is frequently used in clinics and research studies because it is short and easy to administer, with a cut off score of 2 out of 8 items recommended to maximize sensitivity and specificity. This cutoff assumes that all 8 items provide equivalent “information” about everyday functioning. In this study, we used item response theory (IRT) to test this assumption. To determine the relevance of this measure of everyday functioning in men and women, and across race, ethnicity, and education, we conducted differential item functioning (DIF) analysis to test for item bias.Participants and Methods:Data came from the 2021 follow up of the High School & Beyond cohort (N=8,690; mean age 57.5 ± 1.2; 55% women), a nationally representative, longitudinal study of Americans who were first surveyed in 1980 when they were in the 10th or 12th grade. Participants were asked AD8 questions about their own functioning via phone or internet survey. First, we estimated a one-parameter (i.e., differing difficulty, equal discrimination across items) and two-parameter IRT model (i.e., differing difficulty and differing discrimination across items). We compared model fit using a likelihood-ratio test. Second, we tested for uniform and non-uniform DIF on AD8 items by sex, race and ethnicity (non-Hispanic White, non-Hispanic Black, Hispanic), education level (high school or less, some college, BA degree or more), and survey mode (phone or internet). We examined DIF salience by comparing the difference between original and DIF-adjusted AD8 scores to the standard error of measurement of the original score.Results:The two-parameter IRT model fit the data significantly better than the one-parameter model, indicating that some items were more strongly related to underlying everyday functional ability than others. For example, the “problems with judgment” item had higher discrimination (more information) than the “less interest in hobbies/activities” item. There were significant differences in item endorsement by race/ethnicity, education, and survey mode. We found significant uniform and non-uniform DIF on several items across each of these groups. For example, for a given level of functional decline (theta) White participants were more likely to endorse “Daily problems with thinking/memory” than Black and Hispanic participants. The DIF was salient (i.e., caused AD8 scores to change by greater than the standard error of measurement for a large portion of respondents) for those with a college degree and phone respondents.Conclusions:In a population representative sample of Americans ∼age 57, the items on the AD8 contributed differing levels of discrimination along the range of everyday functioning that is impacted by later life cognitive impairment. This suggests that a simple cut-off or summed score may not be appropriate since some items yield more information about the underlying construct than others. Furthermore, we observed significant and salient DIF on several items by education and survey mode, AD8 scores should not be compared across education groups and assessment modes without adjustment for this measurement bias.

Comparing different trend estimation approaches in country means and standard deviations in international large-scale assessment studies

One major aim of international large-scale assessments (ILSA) like PISA is to monitor changes in student performance over time. To accomplish this task, a set of common items (i.e., link items) is repeatedly administered in each assessment. Linking methods based on item response theory (IRT) models are used to align the results from the different assessments on a common scale. This work employs the one-parameter logistic (1PL) and the two-parameter logistic (2PL) IRT models as scaling models for dichotomous item response data. The present article discusses different types of trend estimates in country means and standard deviations for countries in ILSA. These types differ in three aspects. First, the trend can be assessed by an indirect or direct linking approach for linking a country’s performance at an international metric. Second, the linking for the trend estimation can rely on either all items or only the link items. Third, item parameters can be assumed to be invariant or noninvariant across countries. It is shown that the most often employed trend estimation methods of original trends and marginal trends can be conceived as particular cases of indirect and direct linking approaches, respectively. Through a simulation study and analytical derivations, it is demonstrated that trend estimates using a direct linking approach and those that rely on only link items outperformed alternatives for the 1PL model with uniform country differential item functioning (DIF) and the 2PL model with uniform and nonuniform country DIF. We also illustrated the performance of the different scaling models for assessing the PISA trend from PISA 2006 to PISA 2009 in the cognitive domains of reading, mathematics, and science. In this empirical application, linking errors based on jackknifing testlets were utilized that adequately quantify DIF effects in the uncertainty of trend estimates.

Evaluation of psychometric properties of the Dental Anxiety Inventory (DAI-36) questionnaire using iterative hybrid ordinal logistic: Differential item functioning (DIF).

Dental Anxiety Inventory (DAI-36) questionnaire is an instrument for assessing dental anxiety. The different perceptions of the questionnaire items in the individual at the same level of underlying dental anxiety may lead to different reported dental anxieties. This study aims to determine the differential item functioning (DIF) of the DAI-36 measure items. The DAI-36 was completed by 950 participants. An iterative hybrid ordinal logistic regression model was used to detect DIF across gender, education, and age groups. DIF analysis was done by lordif package in R3.1.3 software. The chi-square statistics declared 7, 7, and 4 nonuniform DIF items, and 2, 5, and 4 uniform DIF items across gender, education, and age groups, respectively. ΔR2 was always lower than 0.07 in all uniform and nonuniform DIF items. However, Δβ1 revealed significant uniform DIF in items 1 and 8 across gender (Δβ1(item 1)=0.0137, Δβ1(item 8)=0.0124) and items 22 and 27 across age categories (Δβ1(item 22)=0.0110, Δβ1(item 27)=0.0136). DIF items had no large magnitude or cancel out each other, so statements phrased in the DAI-36 questionnaire have equivalent meaning across participants, regardless of their gender, education, and age groups.

Wald χ2 Test for Differential Item Functioning Detection with Polytomous Items in Multilevel Data

Identifying items with differential item functioning (DIF) in an assessment is a crucial step for achieving equitable measurement. One critical issue that has not been fully addressed with existing studies is how DIF items can be detected when data are multilevel. In the present study, we introduced a Lord’s Wald [Formula: see text] test-based procedure for detecting both uniform and non-uniform DIF with polytomous items in the presence of the ubiquitous multilevel data structure. The proposed approach is a multilevel extension of a two-stage procedure, which identifies anchor items in its first stage and formally evaluates candidate items in the second stage. We applied the Metropolis–Hastings Robbins–Monro (MH-RM) algorithm to estimate multilevel polytomous item response theory (IRT) models and to obtain accurate covariance matrices. To evaluate the performance of the proposed approach, we conducted a preliminary simulation study that considered various conditions to mimic real-world scenarios. The simulation results indicated that the proposed approach has great power for identifying DIF items and well controls the Type I error rate. Limitations and future research directions were also discussed.

Assessment of differential item functioning of the PHQ-9, HADS-D and PROMIS-depression scales in persons with and without multiple sclerosis

ObjectiveWe tested for the presence of differential item functioning (DIF) in commonly used measures of depressive symptoms, in people with multiple sclerosis (MS) versus people with a psychiatric disorder without MS. MethodsParticipants included individuals with MS, or with a lifetime history of a depressive or anxiety disorder (Dep/Anx) but no immune-mediated inflammatory disease. Participants completed the Patient Health Questionnaire (PHQ-9), Hospital Anxiety and Depression Scale (HADS), and the Patient Reported Outcome Measurement Information System (PROMIS)-Depression. We assessed unidimensionality of the measures using factor analysis. We evaluated DIF using logistic regression, with and without adjustment for age, gender and body mass index (BMI). ResultsWe included 555 participants (MS: 252, Dep/Anx: 303). Factor analysis showed that each depression symptom measure had acceptable evidence of unidimensionality. In unadjusted analyses comparing the MS versus Dep/Anx groups we identified multiple items with evidence of DIF, but few items showed DIF effects that were large enough to be clinically meaningful. We observed non-uniform DIF for one PHQ-9 item, and three HADS-D items. We also observed DIF with respect to gender (one HADS-D item), and BMI (one PHQ-9 item). For the MS versus Dep/Anx groups, we no longer observed DIF post-adjustment for age, gender and BMI. On unadjusted and adjusted analyses, we did not observe DIF for any PROMIS-D item. ConclusionOur findings suggest that DIF exists for the PHQ-9 and HADS-D with respect to gender and BMI in clinical samples that include people with MS whereas DIF was not observed for the PROMIS-Depression scale.

Multi-Group Generalizations of SIBTEST and Crossing-SIBTEST

ABSTRACT This article presents generalizations of SIBTEST and crossing-SIBTEST statistics for differential item functioning (DIF) investigations involving more than two groups. After reviewing the original two-group setup for these statistics, a set of multigroup generalizations that support contrast matrices for joint tests of DIF are presented. To investigate the Type I error and power behavior of these generalizations, a Monte Carlo simulation study was then explored. Results indicated that the proposed generalizations are reasonably effective at recovering their respective population parameter definitions, maintain optimal Type I error control, have suitable power to detect uniform and non-uniform DIF, and in shorter tests are competitive with the generalized logistic regression and generalized Mantel–Haenszel tests for DIF.

Do the SCOFF items function differently by food-security status in U.S. college students?: Statistically, but not practically, significant differences

Despite food insecurity (FI) being associated with eating disorders (EDs), little research has examined if ED screening measures perform differently in individuals with FI. This study tested whether items on the SCOFF performed differently as a function of FI. As many people with FI hold multiple marginalized identities, this study also tested if the SCOFF performs differently as a function of food-security status in individuals with different gender identities and different perceived weight statuses. Data were from the 2020/2021 Healthy Minds Study (N = 122,269). Past-year FI was established using the two-item Hunger Vital Sign. Differential item functioning (DIF) assessed whether SCOFF items performed differently (i.e., had different probabilities of endorsement) in groups of individuals with FI versus those without. Both uniform DIF (constant between-group difference in item-endorsement probability across ED pathology) and non-uniform DIF (variable between-group difference in item-endorsement probability across ED pathology) were examined. Several SCOFF items demonstrated both statistically significant uniform and non-uniform DIF (ps < .001), but no instances of DIF reached practical significance (as indicated by effect sizes pseudo ΔR2 ≥ 0.035; all pseudo ΔR2's ≤ 0.006). When stratifying by gender identity and weight status, although most items demonstrated statistically significant DIF, only the SCOFF item measuring body-size perception showed practically significant non-uniform DIF for perceived weight status. Findings suggest the SCOFF is an appropriate screening measure for ED pathology among college students with FI and provide preliminary support for using the SCOFF in individuals with FI and certain marginalized identities.

Differential item functioning detection in fundamental physics test

The study's objective was to identify the differential item functioning (DIF) or bias using item response theory. This research is exploratory research with a quantitative approach. In this study, the data used is a fundamental physics test, specifically motion one and two dimensions, dynamics and work and energy concept, with 25 items in the two-tier multiple choices in form. Two hundred and fifty-four prospective physics teachers at West Java and Banten provinces, Indonesia, consisting of 103 males (reference group) and 151 females (focal group). The data analysis includes two stages: conformity of the logistic model parameters and item characteristics, followed by DIF detection. The model suitability test shows the appropriate parameter is 2PL. DIF detection has three methods: simple area indices, Raju and the Lord method. Research results show two things. First, the model fit test shows that the data best fit the 2-parameter or 2-PL logistic parameter model, and all items have good characteristics. Second, the most significant item containing uniform DIF was number 5, followed by nonuniform DIF items 9 and 25. These three items were biased because the chances of answering correctly for male and female students differed. Significantly, this means that this item favors one group. This study illustrates the importance of constructing instrument items so that all test takers, both male and female, have an equal chance to answer the question correctly. Keywords: Differential item functioning, physics test, simple area indices, Raju method, Lord method;

Item performance across native language groups on the Iranian National University Entrance English Exam: a nationwide study

This paper reports on an investigation of differential item functioning (DIF) in the Iranian Undergraduate University Entrance Special English Exam (IUUESEE) across four native language groups including the Azeri, the Persian, the Kurdish, and the Luri test takers via Rasch analysis. A total sample of 14,172 participants was selected for the study. After establishing the unidimensionality and local independence of the data, the authors employed two methods to test for the DIF: (a) a t-test uniform DIF analysis, which showed that the Luri test-takers were more favored than other native language groups, and (b) nonuniform DIF analysis, which revealed that majority of nonuniform DIF instances functioned in favor of the low-ability Azeri, the low-ability Persian, the high-ability Kurdish, and the high-ability Luri test-takers. A possible explanation for native language-ability DIF was that the Luri and low-ability test-takers were more likely to venture lucky guesses. We also referred to socioeconomic status (e.g., test-wiseness), guessing, overconfidence, thoughtless errors, stem length, time, L1, and unappealing distractors as possible sources of DIF in IUUESEE.

Developing the HLS19-YP12 for measuring health literacy in young people: a latent trait analysis using Rasch modelling and confirmatory factor analysis

BackgroundAccurate and precise measures of health literacy (HL) is supportive for health policy making, tailoring health service design, and ensuring equitable access to health services. According to research, valid and reliable unidimensional HL measurement instruments explicitly targeted at young people (YP) are scarce. Thus, this study aims at assessing the psychometric properties of existing unidimensional instruments and developing an HL instrument suitable for YP aged 16–25 years.MethodsApplying the HLS19-Q47 in computer-assisted telephone interviews, we collected data in a representative sample comprising 890 YP aged 16–25 years in Norway. Applying the partial credit parameterization of the unidimensional Rasch model for polytomous data (PCM) and confirmatory factor analysis (CFA) with categorical variables, we evaluated the psychometric properties of the short versions of the HLS19-Q47; HLS19-Q12, HLS19-SF12, and HLS19-Q12-NO. A new 12-item short version for measuring HL in YP, HLS19-YP12, is suggested.ResultsThe HLS19-Q12 did not display sufficient fit to the PCM, and the HLS19-SF12 was not sufficiently unidimensional. Relative to the PCM, some items in the HLS19-Q12, the HLS19-SF12, and the HLS19-Q12-NO discriminated poorly between participants at high and at low locations on the underlying latent trait. We observed disordered response categories for some items in the HLS19-Q12 and the HLS19-SF12. A few items in the HLS19-Q12, the HLS19-SF12, and the HLS19-Q12-NO displayed either uniform or non-uniform differential item functioning. Applying one-factorial CFA, none of the aforementioned short versions achieved exact fit in terms of non-significant model chi-square statistic, or approximate fit in terms of SRMR ≤ .080 and all entries ≤ .10 that were observed in the respective residual matrix. The newly suggested parsimonious 12-item scale, HLS19-YP12, displayed sufficiently fit to the PCM and achieved approximate fit using one-factorial CFA.ConclusionsCompared to other parsimonious 12-item short versions of HLS19-Q47, the HLS19-YP12 has superior psychometric properties and unconditionally proved its unidimensionality. The HLS19-YP12 offers an efficient and much-needed screening tool for use among YP, which is likely a useful application in processes towards the development and evaluation of health policy and public health work, as well as for use in clinical settings.

Psychometric Assessment of Pilot Language and Communication Items on the 2018 and 2019 National Survey of Children's Health.

Until recently, normative data on language and communication development among children in the United States have not been available to inform critical efforts to promote language development and prevent impairments. This study represents the first psychometric assessment of nationally representative data derived from a National Survey of Children's Health (NSCH) pilot measure of language and communication development among children ages 1 to 5 years. We analyzed 14,573 parent responses to language and communication items on the 2018 and 2019 NSCH to evaluate whether the newly added 11 items represent a single latent trait for language and communication development and to determine normative age of success on each item. We applied weighted, one-parameter Item Response Theory to rate and cluster items by difficulty relative to developmental language ability. We examined differential item functioning (DIF) using weighted logistic regression by demographic factors. Together, exploratory factor analysis resulting in a single factor > 1 and explaining 93% of the variance and positive correlations indicated unidimensionality of the measure. Item characteristic curves indicated groupings were overall concordant with proposed milestone ages and representative of an approximate 90% success cut-point by child age. Indicated normative age cut-points for 3 of the items differed slightly from proposed milestone ages. Uniform DIF was not observed and potential nonuniform DIF was observed across 5 items. Results have the potential to enhance understanding of risk and protective factors, inform efforts to promote language and communication development, and guide programmatic efforts on early detection of language delays.

The Multimodal Listening Test in a High-Stakes Context: Gender-Neutral or not?

ABSTRACT In this study, we used the Rasch measurement to investigate the fairness of the listening section of a national computerized high-stakes English test for differential item functioning (DIF) across gender subgroups. The computerized test format inspired us to investigate whether the items measure listening comprehension differently for females and males. Exploring the functioning of novel task types including multimodal materials such as videos and pictures was especially interesting. Firstly, the unidimensionality and local independence of the data were examined as preconditions for DIF analysis. Secondly, the authors explored the performance of female and male students through DIF analysis using the Rasch measurement. The uniform DIF analysis showed that 25 items (out of 30 items) displayed DIF and favored different gender subgroups, whereas the effect size was not meaningful. The non-uniform DIF analysis revealed several items exhibiting DIF with a moderate to large effect size, favoring various gender and ability groups. Explanations for DIF are hypothesized. Finally, implications of the study regarding test development and fairness are discussed.

Differential Item Functioning: An Examination of the NEO-FFI by Sex in Older Adults

Understanding sex differences when assessing personality in older adults is important for researchers and clinicians. The current study utilized differential item functioning (DIF) to compare male and female older adults’ responses on the NEO-FFI to detect potential sources of measurement bias. Participants included 244 older adults (98 males, 146 females, mean age = 73). DIF by sex was determined using ordinal logistic regression and item response theory.Non-uniform DIF was present in item 31, and uniform DIF was present in item 26 in the Neuroticism scale. In the Extraversion scale, non-uniform DIF was present in items 32 and 37. In the Openness scale, non-uniform DIF was present in items 23 and 48; uniform DIF was present in items 53 and 58. Following Monte Carlo simulations to prevent overidentification, non-uniform DIF was present in item 31 in the Neuroticism scale and item 32 in the Extraversion scale. Results suggest that the NEO-FFI is a minimally biased measurement tool based on sex.

Psychometric evaluation of an Italian custom 4-item short form of the PROMIS anxiety item bank in immune-mediated inflammatory diseases: an item response theory analysis.

BackgroundThere has recently been growing interest in the roles of inflammation in contributing to the development of anxiety in people with immune-mediated inflammatory diseases (IMID). Patient-reported outcome measures can facilitate the assessment of physical and psychological functioning. The National Institutes of Health (NIH)’s Patient-Reported Outcomes Measurement Information System (PROMIS®) is a set of Patient-Reported Outcomes (PROs) that cover physical appearance, mental health, and social health. The PROMIS has been built through an Item Response Theory approach (IRT), a model-based measurement in which trait level estimates depend on both persons’ responses and on the properties of the items that were administered. The aim of this study is to test the psychometric properties of an Italian custom four-item Short Form of the PROMIS Anxiety item bank in a cohort of outpatients with IMIDs.MethodsWe selected four items from the Italian standard Short Form Anxiety 8a and administered them to consecutive outpatients affected by Inflammatory Bowel disease (n = 246), rheumatological (n = 100) and dermatological (n = 43) diseases, and healthy volunteers (n = 280). Data was analyzed through an Item Response Theory (IRT) analysis in order to evaluate the psychometric properties of the Italian adaptation of the PROMIS anxiety short form.ResultsTaken together, Confirmatory Factor Analysis and Exploratory Factor analysis suggest that the unidimensionality assumption of the instrument holds. The instrument has excellent reliability from a Classical Theory of Test (CTT) standpoint (Cronbach’s α = 0.93, McDonald’s ω = 0.92). The 2PL Graded Response Model (GRM) model provided showed a better goodness of fit as compared to the 1PL GRM model, and local independence assumption appears to be met overall. We did not find signs of differential item functioning (DIF) for age and gender, but evidence for uniform (but not non-uniform) DIF was found in three out of four items for the patient vs. control group. Analysis of the test reliability curve suggested that the instrument is most reliable for higher levels of the latent trait of anxiety. The groups of patients exhibited higher levels of anxiety as compared to the control group (ps < 0.001, Bonferroni-corrected). The groups of patients were not different between themselves (p = 1, Bonferroni-corrected). T-scores based on estimated latent trait and raw scores were highly correlated (Pearson’s r = 0.98) and led to similar results.DiscussionThe Italian custom four-item short form from the PROMIS anxiety form 8a shows acceptable psychometric properties both from a CTT and an IRT standpoint. The Test Reliability Curve shows that this instrument is mostly informative for people with higher levels of anxiety, making it particularly suitable for clinical populations such as IMID patients.