Supplemental Material for Investigating Differential Item Functioning Among Borderline Personality Disorder Diagnostic Criteria and Internalizing/Externalizing Domains Based on Sexual Orientation

Several items showed evidence of DIF when symptom-level impairment was considered, evidenced by false discovery rate corrected DIFFTEST values (see These results are challenging to interpret, as the majority of differences in discrimination parameters for SM compared to non-SM groups compared a significant (p < .05)discrimination parameter in the non-SM group to a non-significant discrimination parameter in the SM group.This may be due to the smaller sample size of the symptom-level impairment analyses, and given that the items were less endorsed in the SM group, their relationships to latent internalizing and externalizing were more variable.This is supported in the results examining the factor loadings for the BPD items with symptom-level impairment to internalizing and externalizing.This leads us to believe the discrimination models tended to compare relatively poor discriminability in the non-SM group with next-to-zero discriminability in the SM group.We see this as evidence that BPD items with symptom-level impairment were weak indicators of latent internalizing and externalizing domains, and that the DIFFTEST flagged differences in already poorly fitting models as opposed to substantive, interpretable differences in discrimination parameters across SM status.We report the discrimination results with symptom-level impairment below.Internalizing.Unstable relationships, impulsive sex, and impulsive shopping/gambling more poorly discriminated across internalizing levels in non-SM relative to SM individuals.The inverse was true for efforts to avoid abandonment, sudden changes in identity, identity disturbance 3, and emptiness which more poorly discriminated across internalizing levels in SM relative to non-SM.Discrimination parameters were significant in the SM group for sudden changes in identity, identity disturbance 3, and emptiness.Preventing abandonment, unstable relationships, impulsive sex, and impulsive shopping/gambling did not have significant discrimination parameters.Externalizing.Preventing abandonment and impulsive sex more poorly discriminated across externalizing levels in non-SM relative to SM; however, the inverse was true for identity disturbance 2, impulsive behavior, and deliberate self-harm, which more poorly discriminated