During the consensus meetings of the National Institute of Mental Health Measurement and Treatment Research to Improve Cognition in Schizophrenia (NIMH-MATRICS) Initiative, the U.S. Food and Drug Administration took the position that a drug for this purpose should show changes on 1) an accepted consensus cognitive performance measure and 2) an additional measure (i.e., a co-primary) that is considered functionally meaningful. The goal of the current study was to describe steps to evaluate four potential co-primary measures for psychometric properties and validity.

Green MF, Nuechterlein KH, Kern RS, Baade LE, Fenton WS, Gold JM, Keefe RSE, Mesholam-Gately R, Seidman LJ, Stover E, Marder SR. Functional co-primary measures for clinical trials in schizophrenia:  Results from the MATRICS psychometric and standardization study.  The American Journal of Psychiatry, 2008; 165(2): 221-228.