OBJECTIVE: To test the validity and sensitivity of the six-item version (PANSS-6) of the 30-item Positive and Negative Syndrome Scale (PANSS-30) in treatment-resistant schizophrenia (TRS).

METHOD: Using data from the clozapine phase (2E) of the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) study, we investigated the following: (i) The scalability of PANSS-6 and PANSS-30; (ii) The correlation between PANSS-6 and PANSS-30 total scores; (iii) Whether PANSS-6 could identify cross-sectional symptom remission; and (iv) The efficacy of clozapine, olanzapine, risperidone and quetiapine in TRS using the 'speed of change' on PANSS-6 and PANSS-30 (change in total score per week) as outcome measures.

RESULTS: We found that (i) only PANSS-6 and not PANSS-30 was scalable; (ii) The correlation between PANSS-6 and PANSS-30 total scores was high (Spearman coefficient: 0.85), (iii) PANSS-6 accurately identified cross-sectional symptom remission as defined by the Andreasen et al. criteria; and (iv) The only antipsychotic that caused improvement (speed of change significantly lower than 0 during the first three months of treatment) was clozapine, both when using PANSS-6 (speed of change: -0.50 points/week; 95%CI: -0.84, -0.17) and PANSS-30 (speed of change: -1.41 points/week; 95%CI: -2.80, -0.02) as outcome measures.

CONCLUSION: PANSS-6 validly measures severity, remission and antipsychotic efficacy in TRS.