The Level of Personality Functioning Scale (LPFS) of the Alternative DSM-5 Model for Personality Disorders (AMPD) was formulated to assess the presence and severity of personality disorders (PDs). Moderate impairment (Level 2) in personality functioning, as measured by the LPFS, was incorporated into the AMPD as a diagnostic threshold for PD in Criterion A of the general criteria, as well as for the “any two areas present” rule for assigning a specific PD diagnosis. This study represents the first evaluation of the diagnostic decision rules for Criterion A, in a clinical sample (N = 282). The results indicate that an overall diagnostic threshold for PDs should be used with caution because it may not identify all DSM-IV PDs. The “any two areas present” rule proved to be a reasonable alternative, although this finding should be interpreted with caution because the LPFS does not measure the disorder-specific A criteria.