Time-stability of the "Functional Remission of General Schizophrenia" (FROGS) scale

Functional remission in schizophrenia is an important treatment goal, particularly for patients who have achieved symptomatic remission. The Functional Remission of General Schizophrenia (FROGS) scale has recently been developed, with the FROGS total score being reported as reliable in a cross-sectional study, with an exploratory factor analysis showing three oblique meaningful factors. As such an instrument should have a stable structure over time, but also be able to detect improvement of functioning with time, we have further analysed the validity of the FROGS scale, specifically assessing time-stability. We re-evaluated the initial patient sample around 1.5 years after the first evaluation (mean=17.1 months, standard deviation=1.9), restricting the analyses to patients who were still being followed-up and in clinical remission (n=140 patients). The mean (standard deviation) FROGS total score was 75.82 (10.85) at the second evaluation, showing a significant improvement with time (3.84; P<0.0001 versus the first evaluation). The internal consistency/reliability of the FROGS scale was still very high (Cronbach's α=0.919). Significant improvements between the first and second evaluations were also apparent for all the individual items in the FROGS scale (P<0.01) as well as for the subscores for the three extracted factors (P<0.0001). Statistically significant correlations were observed between the FROGS scale and other indices, including the Global Assessment of Functioning (r=0.58; P<0.0001). These results provide further evidence of the solid psychometric properties of the FROGS scale.