This study addresses the underexplored terrain of conceptualizing and operationalizing race and ethnicity as grouping variables in Differential Item Functioning (DIF) studies within the context of psychometric research. The investigation extends beyond the identification of DIF and delves into the theoretical framing and communication of findings related to these variables. Analyzing 120 articles from diverse academic databases, this research employs descriptive statistics and interviews with two authors in its two-phase mixed methods approach. The results illuminate significant gaps in the current practices of DIF studies utilizing race and ethnicity as grouping variables. Notably, 75% of studies need more operational definitions and theoretical justifications for the inclusion of the race and ethnicity variables. The diversity in the definitions employed, often aligning with census categories, and the varied approaches to participant categorization (57% allowing self-selection, 30% unspecified) underscore the need for methodological clarity. The prevalence of an exploratory approach (83%) to DIF detection, with a limited focus (29%) on threats to internal validity, indicates a nuanced landscape. In conclusion, this study highlights the complexity surrounding the use of race and ethnicity as grouping variables in DIF studies. It emphasizes the necessity for clearer conceptualization, theoretical framing, and interpretation of findings. It advocates for enhanced methodological rigor, transparency, and cross-cultural considerations in psychometric research, paving the way for more nuanced and reliable assessments of differential item functioning across diverse populations. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]