["Journal of Traumatic Stress, EarlyView. ", "\nAbstract\nIndividuals with subthreshold posttraumatic stress disorder (PTSD) often experience significant impairment yet face barriers to care (e.g., insurance denials and exclusion from clinical trials) due to strict Diagnostic and Statistical Manual of Mental Disorders (DSM)–based diagnostic criteria that rely entirely on symptom counts. Symptom counts assume all symptoms contribute equally to underlying (within‐criterion) severity. Recently, item response theory and nonlinear factor analysis models have been used to estimate PTSD severity, accounting for differences in the relative weight of symptoms. We examined a subset of treatment‐seeking adults with comorbid PTSD and substance use disorders in Project Harmony who met the criteria for full PTSD based on weighted severity scores regardless of whether they met the full DSM‐defined criteria. Latent class analysis was then used to identify differences in symptom endorsement patterns in this empirically estimated full‐threshold PTSD group. Three distinct classes were identified: (a) participants with full‐threshold PTSD based on both DSM and weighted classification, (b) underdiagnosed participants who did not endorse either DSM Criterion C (avoidance) symptom, or (c) underdiagnosed participants who only endorsed one DSM Criterion E (alterations in arousal/reactivity) symptom. Endorsement of two DSM Criterion D symptoms (negative alterations in cognitions and mood) did not differ across classes, suggesting that they could be “priority symptoms” indicating high distress and impairment, regardless of DSM diagnostic status or severity level. Accounting for symptom weighting and prioritizing these symptoms in assessment and diagnosis could increase precision in PTSD assessment and ensure equitable access to care.\n"]