Validity of the Functioning Assessment Short Tests (FAST), in patients with schizophrenia

Functional impairment in schizophrenia is one of the main features of the disorder and implies a great impact on the patient's quality of life. The Brief Functioning Assessment Scale (FAST), originally validated in bipolar disorder, has also been validated for its application in other mental disorders. However, we only found one study on the reliability and validity of the Brazilian version in schizophrenia. The purpose of this study was to analyze the psychometric properties of the Spanish version of the FAST in patients diagnosed with schizophrenia.

A total of 226 patients with a diagnosis of schizophrenia were evaluated by mean the FAST, the GAF and the self-care requirements scale (ERA). Scale properties were analyzed in terms of internal consistency, inter-observer agreement and test-retest reliability. Convergent validity with the GAF and ERA scales was also analyzed, as well as construct validity by means of a Confirmatory Factor Analysis (CFA).

For the total scale, the results showed high internal consistency (Cronbach's Alpha of, 87), as well as good inter-observer (ICC=,86) and test-retest (ICC=,77) agreement. Concurrent validity with the GAF scale was discrete (r=-,32; P<,001) and with the ERA scale was moderate (r=,50; P<,001). CFA showed an internal structure that matched the six factors proposed by the original scale, with a good level of item saturation for each factor.

The FAST scale showed good psychometric properties in terms of reliability and validity in its Spanish version for its application in patients with schizophrenia. It can be considered as a good tool to assess different areas of functional impairment in clinical practice and research.