Assessing International Classification of Diseases, 11th revision (ICD-11) borderline psychopathology: Psychometric validation of the German Borderline Pattern Scale (BPS) in a psychiatric sample.

The 11th edition of the International Classification of Diseases introduced a dimensional model of personality disorder diagnosis supplemented by an optional borderline pattern qualifier.The Borderline Pattern Scale (BPS; Oltmanns & Widiger, 2019) is a self-report instrument assessing this qualifier via four symptom clusters: affective instability, maladaptive self-functioning, maladaptive interpersonal functioning, and maladaptive self-regulation strategies.This study translated, adapted, and validated the BPS for German-speaking clinical populations (N = 405) using a back-translation procedure.Psychometric evaluation included internal consistency, test-retest reliability, and factor structure analyses (parallel analysis, exploratory graph analysis) confirmatory factor analysis, as well as construct validity via correlations with the Borderline Symptom List-23 and the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition Screening Personality Questionnaire.Receiver operating characteristic analyses assessed classification accuracy for clinician-assigned borderline personality disorder diagnoses.Results demonstrated excellent internal consistency (α = .89)and test-retest reliability (r = .87).Exploratory graph analysis indicated a robust unidimensional structure, while confirmatory factor analysis supported a hierarchical four-factor model with incremental validity over a unidimensional solution.BPS total scores showed strong convergent validity with the Borderline Symptom List-23 and discriminant validity against nonborderline personality disorder scales.Receiver operating characteristic analyses revealed good classification accuracy (area under the curve = .82),with optimal cutoffs balancing sensitivity and specificity.German BPS scores demonstrate reliability and support multiple sources of validity evidence for their intended interpretation as measures of the 11th edition of the International Classification of Diseases borderline pattern severity.The low internal consistency of the Maladaptive Interpersonal Functioning subscale (ᾰ = .41)warrants caution; the BPS total score is psychometrically preferable for most purposes. Public Significance StatementThis study introduces the first validated German questionnaire assessing borderline personality patterns according to the 11th edition of the International Classification of Diseases.Scores derived from the German Borderline Pattern Scale demonstrated strong reliability and supported multiple sources of validity evidence for their intended interpretation in a psychiatric sample, allowing clinicians and researchers to better identify and understand borderline psychopathology.This facilitates accurate diagnosis, individual case formulation, treatment planning, and international consistency in the 11th edition of the International Classification of Diseases assessment.