Direct immunofluorescence on plucked hair outer root sheath can predict relapse in pemphigus vulgaris.

BACKGROUND: Prospective research is lacking on the utility of plucked hair outer root sheath direct immunofluorescence (ORS DIF) in the prediction of relapse in pemphigus vulgaris (PV) and the correlation of ORS DIF positivity with serum desmoglein antibody titers. METHODS: We performed a prospective cohort study enrolling 80 PV patients in complete clinical remission at a tertiary care center in North India. Study participants underwent ORS DIF at baseline, which was repeated every 3 months. Skin biopsy DIF was done at study inclusion, repeated at 3 months, and upon clinical relapse. An antidesmoglein antibody titer was assessed concurrently with ORS DIF in a subset of patients. Patients on adjuvant therapy had their adjuvant therapy withdrawn either at the initial visit, at 3 months, or at a 6-month follow-up. Our objectives were to determine the association between positive ORS DIF and clinical relapse, the correlation between positive ORS DIF and skin biopsy DIF, and between positive ORS DIF and positive antidesmoglein antibody titers (when concurrently done). RESULTS: Twenty-two patients (27.5%) had a clinical relapse. Baseline immunological markers significantly associated with relapse are ORS DIF positivity with IgG (16/36 [45.44%] P = 0.005) and C3 (12/29 [41.37%] P = 0.047) and greater intensity of baseline IgG and C3 positivity in ORS DIF (IgG, P = 0.002; C3, P = 0.033). Notably, a significant correlation was observed between baseline positive ORS DIF and skin biopsy DIF (IgG, ρ = 0.695; C3, ρ = 0.498). Positive ORS DIF strongly correlated with positive anti-Dsg3 antibody titers (φs = 0.815; P < 0.01). Early withdrawal of adjuvant immunosuppressant (within 3 months) (P = 0.007) and positive ORS DIF were also associated with relapse (P = 0.017). CONCLUSION AND RELEVANCE: ORS DIF is a reliable predictor of PV clinical relapse and demonstrated robust correlations with skin biopsy DIF and antidesmoglein antibody titers. Periodic assessment of ORS DIF aids in determining new-onset positivity that heralds clinical relapse.

Mapping intersectional sociodemographic inequalities in measurement and prevalence of depressive symptoms: a intersectional multilevel analysis of individual heterogeneity and discriminatory accuracy using data from a population-based nationwide survey in Germany.

OBJECTIVES: Understanding how social categories like gender, migration background, lesbian/gay/bisexual/transgender (LGBT) status, education, and their intersections affect health outcomes is crucial. Challenges include avoiding stereotypes and fairly assessing health outcomes. This paper aims to demonstrate how to analyze these aspects. STUDY DESIGN AND SETTING: The study used data from N = 19,994 respondents from the German Socio-Economic Panel 2021 data collection. Variations between and within intersectional social categories regarding depressive symptoms and self-reported depression diagnosis were analyzed. We employed intersectional Multilevel Analysis of Individual Heterogeneity and Discriminatory Accuracy to assess the impact of gender, lesbian/gay/bisexual/transgender status, migration, education, and their interconnectedness. A Configuration-Frequency Analysis assessed typicality of intersections. Differential Item Functioning analysis was conducted to check for biases in questionnaire items. RESULTS: Intersectional multilevel analysis of individual heterogeneity and discriminatory accuracy analysis revealed significant interactions between these categories for depressive symptoms and depression diagnosis. The Configuration-Frequency Analysis showed that certain combinations of social categories occurred less frequently compared to their expected distribution. The Differential Item Functioning analysis showed no significant bias in a depression short scale across social categories. CONCLUSION: Results reveal interconnectedness between the social categories, affecting depressive symptoms and depression probabilities. More privileged groups had significant protective effects, while those with less societal privileges showed significant hazardous effects. Statistical significance was found in some interactions between categories. The variance within categories outweighs that between them, cautioning against individual-level conclusions.

Experimental Study on Dynamic Mechanical Performance of Post-Fire Concrete Confined by CFRP Sheets.

Impact tests on post-fire concrete confined by Carbon Fiber-Reinforced Polymer/Plastic (CFRP) sheets were carried out by using Split Hopkinson Pressure Bar (SHPB) experimental setup in this paper, with emphasis on the effect of exposed temperatures, CFRP layers and impact velocities. Firstly, according to the measured stress-strain curves, the effects of experiment parameters on concrete dynamic mechanical performance such as compressive strength, ultimate strain and energy absorption are discussed in details. Additionally, temperature caused a softening effect on the compressive strength of concrete specimens, while CFRP confinement and strain rate play a hardening effect, which can lead to the increase in dynamic compressive strength by 1.8 to 3.6 times compared to static conditions. However, their hardening mechanisms and action stages are extremely different. Finally, nine widely accepted Dynamic Increase Factor (DIF) models considering strain rate effect were summarized, and a simplified model evaluating dynamic compressive strength of post-fire concrete confined by CFRP sheets was proposed, which can provide evidence for engineering emergency repair after fire accidents.

A longer-chain acylated derivative of Dictyostelium differentiation-inducing factor-1 enhances the antimalarial activity against Plasmodium parasites.

The spread of malarial parasites resistant to first-line treatments such as artemisinin combination therapies is a global health concern. Differentiation-inducing factor 1 (DIF-1) is a chlorinated alkylphenone (1-(3,5-dichloro-2,6-dihydroxy-4-methoxyphenyl) hexan-1-one) originally found in the cellular slime mould Dictyostelium discoideum. We previously showed that some derivatives of DIF-1, particularly DIF-1(+2) (1-(3,5-dichloro-2,6-dihydroxy-4-methoxyphenyl) octan-1-one), exert potent antimalarial activities. In this study, we synthesised DIF-1(+3) (1-(3,5-dichloro-2,6-dihydroxy-4-methoxyphenyl) nonan-1-one). We then evaluated the effects of DIF-1(+3) in vitro on Plasmodium falciparum and in vivo over 7 days (50-100 mg/kg/day) in a mouse model of Plasmodium berghei. DIF-1(+3) exhibited a half-maximal inhibitory concentration of approximately 20-30 % of DIF-1(+2) in three laboratory strains with a selectivity index > 263, including in strains resistant to chloroquine and artemisinin. Parasite growth and multiplication were almost completely suppressed by treatment with 100 mg/kg DIF-1(+3). The survival time of infected mice was significantly increased (P = 0.006) with no apparent adverse effects. In summary, addition of an acyl group to DIF-1(+2) to prepare DIF-1(+3) substantially enhanced antimalarial activity, even in drug-resistant malaria, indicating the potential of applying DIF-1(+3) for malaria treatment.

Role of C4d immunohistochemical marker in the diagnosis of bullous pemphigoid: A cross-sectional study.

Objective To determine the diagnostic utility of C4d immunohistochemical marker in cases of bullous pemphigoid by calculating the sensitivity, specificity, positive predictive value and negative predictive value. Methods We conducted an exploratory study (retrospectively and prospectively) from January 2017 to June 2022. All direct immunofluorescence proven cases of bullous pemphigoid were included in the study while cases with inadequate tissue for immunohistochemistry studies were excluded. Results Among the 57 cases of bullous pemphigoid, 49 showed positivity for C4d marker. All the ten control cases of inflammatory dermatoses were negative for C4d staining. A sensitivity of 86%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value of 55.56% were calculated with a confidence interval of 95%. Conclusion Direct immunofluorescence on fresh or frozen skin tissue remains the gold standard. But in circumstances where direct immunofluorescence facilities are not available, C4d immunohistochemistry marker staining on formalin-fixed paraffin-embedded material submitted for standard microscopic investigation can, in most cases, confirm the diagnosis of bullous pemphigoid, obviating the need for a second biopsy. Limitation It is a single centre study. Selection bias may come into play.

Evaluating the Validity and Measurement Invariance of the Patient Health Questionnaire-9 Among Canadian Nurses.

Background and Purpose: The patient health questionnaire 9 item (PHQ-9) is a widely used self-reported measure for screening depressive symptoms. This study aims to examine measurement invariance and psychometric properties of the PHQ-9 for screening depressive symptoms in nurses across different nursing roles, gender, and workplace sector. Methods: The study is a secondary analysis of pre-COVID and COVID-19 survey data from 4,176 nurses and 3,238 nurses in British Columbia. Data from the PHQ-9 tested the assumption of unidimensionality, reliability, and presence of differential item functioning (DIF). Results: The PHQ-9 showed excellent internal consistency (r = .9) and a unidimensional factor structure. PHQ-9 items were free of DIF across nursing roles, gender, and workplace sector. Conclusions: This study supported the valid use of the PHQ-9 as a screening tool for depressive symptoms among nurses.

Variation in the plasmid backbone and dif module content of R3-T33 Acinetobacter plasmids.

The predominant type of plasmids found in Acinetobacter species encode a Rep_3 initiation protein and many of these carry their accessory genes in dif modules. Here, available sequences of the 14 members of the group of Rep_3 plasmids typed as R3-T33, using a threshold of 95% identity in the repA gene, were compiled and compared. These plasmids were from various Acinetobacter species. The pdif sites were identified allowing the backbone and dif modules to be defined. As for other Rep_3 plasmids carrying dif modules, orfX encoding a protein of unknown function was found downstream of repA followed by a pdif site in the orientation XerC binding site-spacer-XerD binding site. Most backbones (n = 12) also included mobA and mobC genes but the two plasmids with the most diverged repA and orfX genes had different backbone contents. Although the gene content of the plasmid backbone was largely conserved, extensive recombinational exchange was detected and only two small groups carried identical or nearly identical backbones. Individual plasmids were associated with 1 to 13 dif modules. Many different dif modules were identified, including ones containing antibiotic or chromate resistance genes and several toxin/antitoxin gene pairs. In some cases, modules carrying the same genes were significantly diverged. Generally, the orientation of the pdif sites alternated such that C modules (XerC binding sites internal) alternated with D modules (XerD binding sites internal). However, fusions of two dif modules via mutational inactivation or loss of a pdif site were also detected.

The NFκB Dif is required for behavioral and molecular correlates of sleep homeostasis in Drosophila.

The nuclear factor binding the κ light chain in B-cells (NFκB) is involved in a wide range of cellular processes including development, growth, innate immunity, and sleep. However, genetic studies of the role of specific NFκB transcription factors in sleep have been limited. Drosophila fruit flies carry three genes encoding NFκB transcription factors, Dorsal, Dorsal Immunity Factor (Dif), and Relish. We previously found that loss of the Relish gene from fat body suppressed daily nighttime sleep, and abolished infection-induced sleep. Here we show that Dif regulates daily sleep and recovery sleep following prolonged wakefulness. Mutants of Dif showed reduced daily sleep and suppressed recovery in response to sleep deprivation. Pan-neuronal knockdown of Dif strongly suppressed daily sleep, indicating that in contrast to Relish, Dif functions from the central nervous system to regulate sleep. Based on the unique expression pattern of a Dif- GAL4 driver, we hypothesized that its effects on sleep were mediated by the pars intercerebralis (PI). While RNAi knock-down of Dif in the PI reduced daily sleep, it had no effect on the recovery response to sleep deprivation. However, recovery sleep was suppressed when RNAi knock-down of Dif was distributed across a wider range of neurons. Induction of the nemuri (nur) antimicrobial peptide by sleep deprivation was reduced in Dif mutants and pan-neuronal overexpression of nur also suppressed the Dif mutant phenotype by significantly increasing sleep and reducing nighttime arousability. Together, these findings indicate that Dif functions from brain to target nemuri and to promote deep sleep.

The inhibitory effect of DIF-3 on polyinosinic-polycytidylic acid-induced innate immunity activation in human cerebral microvascular endothelial cells.

For the treatment and prevention of autoinflammatory diseases, it is essential to develop the drug, regulating the innate immune system. Although differentiation-inducing factor (DIF) derivatives, extracted from the cellular slime mold, Dictyostelium discoideum, exhibit immunomodulatory effects, their effects on the regulation of innate immunity in brain are unknown. In this study, we used the human cerebral microvascular endothelial cell line, hCMEC/D3, to investigate the effects of DIF derivatives on the generation of C-X-C motif chemokine (CXCL) 10 and interferon (IFN)-ß induced by polyinosinic-polycytidylic acid (poly IC). DIF-3 (1-10 µM), but not DIF-1 and DIF-2, dose-dependently inhibited the biosynthesis of not only CXCL10 but also CXCL16 and C-C motif chemokine 2 induced by poly IC. DIF-3 also strongly decreased IFN-ß mRNA expression and protein release from the cells induced by poly IC through the prohibition of p65, a subtype of NF-ĸB, not interferon regulatory transcription factor 3 phosphorylation. In the docking simulation study, we confirmed that DIF-3 had a high affinity to p65. These results suggest that DIF-3 regulates the innate immune system by inhibiting TLR3/IFN-ß signaling axis through the NF-ĸB phosphorylation inhibition.

To interpret and analyze the changing patterns of histology and direct immunofluorescence findings in membranoproliferative glomerulonephritis.

Background: Membranoproliferative glomerulonephritis has in the recent past been regrouped into immune complex-mediated (ICM MPGN) disease (driven by the classical complement pathway) and complement-mediated (C3GN) disease (driven by the alternative complement pathway) based on pathogenetic role of alternative complement pathway and immunofluorescence deposits. The proposed regrouping lent therapeutic and prognostic support in managing the disease of MPGN. Aims and Objectives: The present study is undertaken to study the patterns of MPGN based on histopathological and DIF examination and sub-categorize the cases into mainly complement dominant and immune complex-mediated diseases for better prognostic and therapeutic utility. Materials and Methods: This is a prospective observational study carried out in a tertiary care center over a period of 2 yrs. The clinically suspected cases of MPGN were subjected to histopathologic and direct immunofluorescence examination (DIF), and the findings were interpreted in light of complement-mediated and immune complex-mediated MPGN. Results: Out of 620 renal biopsies, diagnosis of MPGN was confirmed both on histopathology and DIF in 36 cases accounting for 5.8% of all biopsies. Based on DIF findings, the various groups comprised 20 cases (55.6%) of immune complex deposits, 11 (30.5%) of C3 dominant picture, and 5 (13.9%) of Nil immune deposits. On analysis of the patterns on DIF, 16 cases (80%) of C3 + Ig group and 6 (54.5%) of C3GN group showed predominantly MPGN pattern. Crescentic glomerulonephritis, global glomerulosclerosis, and interstitial fibrosis were markedly observed in C3GN group. Conclusion: DIF is of immense prognostic and therapeutic value in managing cases of MPGN.

DIF Analysis with Unknown Groups and Anchor Items.

Ensuring fairness in instruments like survey questionnaires or educational tests is crucial. One way to address this is by a Differential Item Functioning (DIF) analysis, which examines if different subgroups respond differently to a particular item, controlling for their overall latent construct level. DIF analysis is typically conducted to assess measurement invariance at the item level. Traditional DIF analysis methods require knowing the comparison groups (reference and focal groups) and anchor items (a subset of DIF-free items). Such prior knowledge may not always be available, and psychometric methods have been proposed for DIF analysis when one piece of information is unknown. More specifically, when the comparison groups are unknown while anchor items are known, latent DIF analysis methods have been proposed that estimate the unknown groups by latent classes. When anchor items are unknown while comparison groups are known, methods have also been proposed, typically under a sparsity assumption - the number of DIF items is not too large. However, DIF analysis when both pieces of information are unknown has not received much attention. This paper proposes a general statistical framework under this setting. In the proposed framework, we model the unknown groups by latent classes and introduce item-specific DIF parameters to capture the DIF effects. Assuming the number of DIF items is relatively small, an L 1 -regularised estimator is proposed to simultaneously identify the latent classes and the DIF items. A computationally efficient Expectation-Maximisation (EM) algorithm is developed to solve the non-smooth optimisation problem for the regularised estimator. The performance of the proposed method is evaluated by simulation studies and an application to item response data from a real-world educational test.

Dictyostelium Differentiation-Inducing Factor 1 Promotes Glucose Uptake via Direct Inhibition of Mitochondrial Malate Dehydrogenase in Mouse 3T3-L1 Cells.

Differentiation-inducing factor 1 (DIF-1), found in Dictyostelium discoideum, has antiproliferative and glucose-uptake-promoting activities in mammalian cells. DIF-1 is a potential lead for the development of antitumor and/or antiobesity/antidiabetes drugs, but the mechanisms underlying its actions have not been fully elucidated. In this study, we searched for target molecules of DIF-1 that mediate the actions of DIF-1 in mammalian cells by identifying DIF-1-binding proteins in human cervical cancer HeLa cells and mouse 3T3-L1 fibroblast cells using affinity chromatography and liquid chromatography-tandem mass spectrometry and found mitochondrial malate dehydrogenase (MDH2) to be a DIF-1-binding protein in both cell lines. Since DIF-1 has been shown to directly inhibit MDH2 activity, we compared the effects of DIF-1 and the MDH2 inhibitor LW6 on the growth of HeLa and 3T3-L1 cells and on glucose uptake in confluent 3T3-L1 cells in vitro. In both HeLa and 3T3-L1 cells, DIF-1 at 10-40 µM dose-dependently suppressed growth, whereas LW6 at 20 µM, but not at 2-10 µM, significantly suppressed growth in these cells. In confluent 3T3-L1 cells, DIF-1 at 10-40 µM significantly promoted glucose uptake, with the strongest effect at 20 µM DIF-1, whereas LW6 at 2-20 µM significantly promoted glucose uptake, with the strongest effect at 10 µM LW6. Western blot analyses showed that LW6 (10 µM) and DIF-1 (20 µM) phosphorylated and, thus, activated AMP kinase in 3T3-L1 cells. Our results suggest that MDH2 inhibition can suppress cell growth and promote glucose uptake in the cells, but appears to promote glucose uptake more strongly than it suppresses cell growth. Thus, DIF-1 may promote glucose uptake, at least in part, via direct inhibition of MDH2 and a subsequent activation of AMP kinase in 3T3-L1 cells.

Pharmacological Evidence That Dictyostelium Differentiation-Inducing Factor 1 Promotes Glucose Uptake Partly via an Increase in Intracellular cAMP Content in Mouse 3T3-L1 Cells.

Differentiation-inducing factor 1 (DIF-1) isolated from the cellular slime mold Dictyostelium discoideum can inhibit mammalian calmodulin-dependent cAMP/cGMP phosphodiesterase (PDE1) in vitro. DIF-1 also promotes glucose uptake, at least in part, via a mitochondria- and AMPK-dependent pathway in mouse 3T3-L1 fibroblast cells, but the mechanism underlying this effect has not been fully elucidated. In this study, we investigated the effects of DIF-1 on intracellular cAMP and cGMP levels, as well as the effects that DIF-1 and several compounds that increase cAMP and cGMP levels have on glucose uptake in confluent 3T3-L1 cells. DIF-1 at 20 µM (a concentration that promotes glucose uptake) increased the level of intracellular cAMP by about 20% but did not affect the level of intracellular cGMP. Neither the PDE1 inhibitor 8-methoxymethyl-3-isobutyl-1-methylxanthine at 10-200 µM nor the broad-range PDE inhibitor 3-isobutyl-1-methylxanthine at 40-400 µM had any marked effects on glucose uptake. The membrane-permeable cAMP analog 8-bromo-cAMP at 200-1000 µM significantly promoted glucose uptake (by 20-25%), whereas the membrane-permeable cGMP analog 8-bromo-cGMP at 3-100 µM did not affect glucose uptake. The adenylate cyclase activator forskolin at 1-10 µM promoted glucose uptake by 20-30%. Thus, DIF-1 may promote glucose uptake by 3T3-L1 cells, at least in part, via an increase in intracellular cAMP level.

Uncovering Differential Item Functioning effects using MIMIC and mediated MIMIC models.

The aim of this study was twofold: first, to examine the presence of bias across gender in a scholastic achievement test named the Academic Achievement Test (AAT) for the Science Track. Second, to understand the underlying mechanism that causes these bias effects by examining the effect of general cognitive ability as a mediator. The sample consisted of 1,300 Saudi high school students randomly selected from a larger pool of 173,133 participants to reduce the effects of excessive power. To examine both goals, the Multiple Indicators Multiple Causes (MIMIC) approach for detecting Differential Item Functioning (DIF) items was used. The results showed that 13 AAT items exhibited DIF effects for different gender groups. In most of these items, male participants were more likely to answer them correctly than their female counterparts. Next, the mediated MIMIC approach was applied to explore possible underlying mechanisms that explain these DIF effects. The results from this study showed that general cognitive ability (i.e., General Aptitude Test - GAT) seems to be a factor that could explain why an AAT item exhibits DIF across gender. It was found that GAT scores fully explain the DIF effect in two AAT items (full mediation). In most other cases, GAT helps account for only a proportion of the DIF effect (partial mediation). The results from this study will help experts improve the quality of their instruments by identifying DIF items and deciding how to revise them, considering the mediator's effect on participants' responses.

Gender-Based Differential Item Function for the Positive and Negative Semantic Dimensions of the Relationship Satisfaction Scale with Item Response Theory.

Relationship satisfaction is at the core of a robust social life and is essential to mental health. The positive and negative semantic dimensions of the relationship satisfaction (PN-SMD) scale is considered in the field of relationship studies to be a reliable tool for assessing the quality of a person's interpersonal relationships. This study evaluated the psychometric properties of the PN-SMD scale by conducting multidimensional item response theory (MIRT) and differential item functioning (DIF) analyses, both of which are emerging assessment methods that focus on individual items. We recruited 511 Chinese undergraduate students for this study. Construct validity, internal consistency, and concurrent validity were assessed, and MIRT and DIF analyses were conducted. Five of the 14 items were found to have gender-based DIF traits, affecting the scale's construct validity. A revised nine-item scale (DIF items excluded) had a significantly better model fit and demonstrated comparable concurrent validity to the original scale. The implications of our results and future research directions are discussed.

The NFκB Dif is required for behavioral and molecular correlates of sleep homeostasis in Drosophila.

The nuclear factor binding the κ light chain in B-cells (NFκB) is involved in a wide range of cellular processes including development, growth, innate immunity, and sleep. However, efforts have been limited toward understanding how specific NFκB transcription factors function in sleep. Drosophila fruit flies carry three genes encoding NFκB transcription factors, Dorsal, Dorsal Immunity Factor (Dif), and Relish. We previously found that loss of the Relish gene from fat body suppressed daily nighttime sleep, and abolished infection-induced sleep. Here we show that Dif regulates daily sleep and recovery sleep following prolonged wakefulness. Mutants of Dif showed reduced daily sleep and suppressed recovery in response to sleep deprivation. Pan-neuronal knockdown of Dif strongly suppressed daily sleep, indicating that in contrast to Relish, Dif functions from the central nervous system to regulate sleep. Based on the distribution of a Dif-associated GAL4 driver, we hypothesized that its effects on sleep were mediated by the pars intercerebralis (PI). While RNAi knock-down of Dif in the PI reduced daily sleep, it had no effect on the recovery response to sleep deprivation. However, recovery sleep was suppressed when RNAi knock-down of Dif was distributed across a wider range of neurons. Induction of the nemuri (nur) antimicrobial peptide by sleep deprivation was suppressed in Dif mutants and pan-neuronal over-expression of nur also suppressed the Dif mutant phenotype. Together, these findings indicate that Dif functions from brain to target nemuri and to promote sleep.

Identification of sources of DIF using covariates in patient-reported outcome measures: a simulation study comparing two approaches based on Rasch family models.

When analyzing patient-reported outcome (PRO) data, sources of differential item functioning (DIF) can be multiple and there may be more than one covariate of interest. Hence, it could be of great interest to disentangle their effects. Yet, in the literature on PRO measures, there are many studies where DIF detection is applied separately and independently for each covariate under examination. With such an approach, the covariates under investigation are not introduced together in the analysis, preventing from simultaneously studying their potential DIF effects on the questionnaire items. One issue, among others, is that it may lead to the detection of false-positive effects when covariates are correlated. To overcome this issue, we developed two new algorithms (namely ROSALI-DIF FORWARD and ROSALI-DIF BACKWARD). Our aim was to obtain an iterative item-by-item DIF detection method based on Rasch family models that enable to adjust group comparisons for DIF in presence of two binary covariates. Both algorithms were evaluated through a simulation study under various conditions aiming to be representative of health research contexts. The performance of the algorithms was assessed using: (i) the rates of false and correct detection of DIF, (ii) the DIF size and form recovery, and (iii) the bias in the latent variable level estimation. We compared the performance of the ROSALI-DIF algorithms to the one of another approach based on likelihood penalization. For both algorithms, the rate of false detection of DIF was close to 5%. The DIF size and form influenced the rates of correct detection of DIF. Rates of correct detection was higher with increasing DIF size. Besides, the algorithm fairly identified homogeneous differences in the item threshold parameters, but had more difficulties identifying non-homogeneous differences. Over all, the ROSALI-DIF algorithms performed better than the penalized likelihood approach. Integrating several covariates during the DIF detection process may allow a better assessment and understanding of DIF. This study provides valuable insights regarding the performance of different approaches that could be undertaken to fulfill this aim.

Pediatric Symptom Checklist-17: Factor Structure and Uniform Differential Item Functioning Across Gender and Age in HIV Orphans and Vulnerable Children in Zambia.

This study aimed to investigate the psychometric properties of the Pediatric Symptom Checklist-17 (PSC-17) in a sample of children orphaned or made vulnerable (OVC) by HIV in Zambia. Caregivers of 1,076 OVC (55.1% boys; Mage = 12.91 years) completed the PSC-17. Competing models, including confirmatory factor analysis (CFA), hierarchical CFA, bifactor CFA, exploratory structural equation modeling (ESEM), and bifactor ESEM, were tested to evaluate the optimal factor structure of the PSC-17. Results showed that the bifactor ESEM provided the best approximation of the PSC-17 data with a well-defined general psychosocial problems factor explaining 72% of the reliable variance in the total score and an internalizing factor containing 63% of reliable variance unique from the general factor. The observed overall psychosocial problems score was associated with lower academic achievement and working memory (with small effect sizes), supporting the discriminant validity of score interpretation. Results of multiple indicators multiple causes (MIMIC) analyses revealed that all items functioned equivalently across child gender and age.

A Robust Method for Detecting Item Misfit in Large-Scale Assessments.

Viable methods for the identification of item misfit or Differential Item Functioning (DIF) are central to scale construction and sound measurement. Many approaches rely on the derivation of a limiting distribution under the assumption that a certain model fits the data perfectly. Typical DIF assumptions such as the monotonicity and population independence of item functions are present even in classical test theory but are more explicitly stated when using item response theory or other latent variable models for the assessment of item fit. The work presented here provides a robust approach for DIF detection that does not assume perfect model data fit, but rather uses Tukey's concept of contaminated distributions. The approach uses robust outlier detection to flag items for which adequate model data fit cannot be established.

Derivatives of Differentiation-Inducing Factor 1 Differentially Control Chemotaxis and Stalk Cell Differentiation in Dictyostelium discoideum.

Differentiation-inducing factors 1 and 2 (DIF-1 and DIF-2) are small lipophilic signal molecules that induce stalk cell differentiation but differentially modulate chemotaxis toward cAMP in the cellular slime mold Dictyostelium discoideum; DIF-1 suppresses chemotactic cell movement in shallow cAMP gradients, whereas DIF-2 promotes it. The receptor(s) for DIF-1 and DIF-2 have not yet been identified. We examined the effects of nine derivatives of DIF-1 on chemotactic cell movement toward cAMP and compared their chemotaxis-modulating activity and stalk cell differentiation-inducing activity in wild-type and mutant strains. The DIF derivatives differentially affected chemotaxis and stalk cell differentiation; for example, TM-DIF-1 suppressed chemotaxis and showed poor stalk-inducing activity, DIF-1(3M) suppressed chemotaxis and showed strong stalk-inducing activity, and TH-DIF-1 promoted chemotaxis. These results suggest that DIF-1 and DIF-2 have at least three receptors: one for stalk cell induction and two for chemotaxis modulation. In addition, our results show that the DIF derivatives can be used to analyze the DIF-signaling pathways in D. discoideum.