Objective
Borderline personality disorder (BPD) is a serious and extremely prevalent mental disorder. Early diagnosis is vital for treatment. However, there are no specific screening instruments validated for Brazilian Portuguese. This study aimed to adapt the McLean Screening Instrument for Borderline Personality Disorder (MSI-BPD) to the Brazilian context. The MSI-BPD is a self-report instrument based on the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5), that enables fast and reliable assessment of BPD, with measures of sensitivity (SN) and specificity (SP) similar to the diagnostic interview for the DSM-5 (Structured Clinical Interview for DSM-V Axis II Disorders [SCID-II]), taken as the gold standard.

Methods
Two independent translations, a synthesis version, back-translation, and analysis by experts were employed to create the final version of the instrument in Brazilian Portuguese. The translated instrument was administered to 1,702 adults aged 18-59 years to verify evidence of validity relating to content, internal structure, relationship with other variables, and reliability.

Results
The exploratory and confirmatory factor analyses show that the one-factor structure is adequate. The scale showed satisfactory internal consistency (Kuder-Richardson coefficient [KR-20] of Cronbach’s alpha = 0.691) and good test-retest reliability (intraclass correlation coefficient [ICC] = 0.802). Logistic regression analysis using the Personality Inventory for the DSM-5-Brief Form (PID-5-BF) (DSM-5) as reference established an ideal cut-off point of eight symptoms, with adequate SN (0.79) and SP (0.75), similar to the original instrument. The area under the curve (AUC) was 0.830 (95% confidence interval: 0.802-0.858), with a positive predictive value of 89.2%.

Conclusion
The Brazilian version of the MSI-BPD has adequate psychometric properties for use as a BPD screening tool by clinicians.