Validation of a functional remission threshold for the Functional Remission of General Schizophrenia (FROGS) scale

Objective: The aim of this study was to develop a functional remission threshold for the Functional Remission Of General Schizophrenia (FROGS) scale, and test its validity regarding clinical and quality of life outcomes.

Design: Cross-sectional study.

Inclusion criteria: Schizophrenia according to DSM-IV-TR criteria.

Data collection: Functioning was assessed using the FROGS and the Global Assessment of Functioning (GAF) scales; psychotic symptoms using the Positive and Negative Syndrome Scale; memory, attention, and executive functions were assessed using the California Verbal Learning Test, the D2 attention task, the Stroop color-word test, the verbal fluency test, the Trail Making Test A and B and the Wechsler Adult Intelligence Scale; and quality of life using the schizophrenia quality of life (S-QoL 18) scale.

Analysis: A logistic regression analysis including the different dimensions of the FROGS was used to create a composite score to classify patients into remitted and non-remitted according a gold standard (cut-off: GAF>= 61). Receiver operating characteristics analyses were then performed to determine the area under the curve (AUC).

Results: Of 137 patients enrolled, 26 were functionally remitted and 111 were not remitted according to GAF score. The AUC for the combination of the FROGS's dimensions to detect functional remission was 0.903 (p<0.001). Sensitivity and specificity for the combination of the FROGS dimensions using the Youden index were 88.5 [69.8; 97.6] and 81.1 [72.5; 87.9], respectively. Validity of this combination was satisfactory. Patients in functional remission had a lower severity of the disease, especially for PANSS negative (p<0.001) and general psychopathology (p<0.001) symptoms. Only two cognitive functions (i.e. fluency and episodic memory) were improved in remitted patients. Higher quality of life levels were globally associated with better functioning.

Conclusions: These findings provide for first accurate FROGS thresholds to detect functional remission in schizophrenia.