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Previous research has demonstrated that differential item functioning (DIF) methods that do not account for multilevel data structure could result in too frequent rejection of the null hypothesis (i.e., no DIF) when the intraclass correlation coefficient (ρ) of the studied item was the same as the ρ of the total score. The current study extended previous research by comparing the performance of DIF methods when ρ of the studied item was less than ρ of the total score, a condition that may be observed with considerable frequency in practice. The performance of two simple and frequently used DIF methods that do not account for multilevel data structure, the Mantel–Haenszel test (MH) and logistic regression (LR), was compared with the performance of a complex and less frequently used DIF method that does account for multilevel data structure, hierarchical logistic regression (HLR). Simulation indicated that HLR and LR performed equivalently in terms of significance tests under most conditions, and MH was conservative across most of the conditions. Effect size estimate of HLR was equally accurate and consistent as effect size estimates of LR and MH under the Rasch model and was more accurate and consistent than LR and MH effect size estimates under the two-parameter item response theory model. The results of the current study provide evidence to help researchers further understand the comparative performance between complex and simple modeling for DIF detection under multilevel data structure. [ABSTRACT FROM PUBLISHER]

Background: Human amniotic mesenchymal stem cells (hAMSCs) are being widely applied in various fields. Therefore, hAMSCs represent a promising candidate to facilitate cartilage regeneration. Nonetheless, no studies have investigated the application of hAMSC sheets to repair cartilage defects in vivo. Purpose: To evaluate hAMSC sheets encapsulating cartilage particles to promote repair of rabbit osteochondral defects. Study Design: Controlled laboratory study. Methods: hAMSC sheets were constructed with passage 3 hAMSCs. The phenotypic and structural characteristics of hAMSC sheets were evaluated by flow cytometry and scanning electron microscopy, respectively. The potential for chondrogenic differentiation of hAMSC sheets was assessed by cartilage-specific marker staining, immunohistochemistry, and mRNA and protein expression (SOX9, COLII, and ACAN). Osteochondral defects (diameter, 3.5 mm; depth, 3 mm) were created in the left patellar grooves of 20 New Zealand White rabbits (female or male). The defects were treated with hAMSC sheet/cartilage particles (n = 5), cartilage particles (n = 5), hAMSC sheets (n = 5), or fibrin glue (n = 5). Macroscopic and histological evaluations of the regenerated tissue were conducted after 3 months. The survival time and differentiation of transplanted hAMSCs in the defect area were evaluated by immunofluorescence. Results: hAMSC sheets had a multilayered structure, with cells stacked layer by layer. Importantly, hAMSC sheets highly expressed phenotypic markers of mesenchymal stem cells. Cartilage-specific marker staining and immunohistochemistry were positive, and mRNA and protein expression was higher in the chondrogenically induced hAMSC sheet group than in the hAMSC sheet group (P <.05). hAMSC sheet/cartilage particles formed a large amount of hyaline-like cartilage in the defect area. In addition, macroscopic and histological scores were significantly higher than those in the other groups. Integration with surrounding normal cartilage and subchondral bone regeneration in the hAMSC sheet/cartilage particles group were better when compared with the other groups. A large number of human nuclear-specific antigen-positive cells were observed in the defect area of hAMSC sheet/cartilage particles and hAMSC sheet groups. Moreover, some positive cells expressed SOX9. Conclusion: hAMSC sheets encapsulating cartilage particles facilitate osteochondral defect repair. Clinical Relevance: Delivery of cells in the form of a cell sheet in conjunction with cartilage particles provides a novel approach for cell-based cartilage regeneration. [ABSTRACT FROM AUTHOR]