In this study we assess the sensitivity of REF scale to detect the disorganization of patient's mental state longitudinally.

Participants: It's a 35-year-old man diagnosed with Schizotypal Personality Disorder. He had a psychotic breakdown and he is being treated with haloperidol. The psychological intervention is cognitive type.

Design, materials and procedure: We used an experimental adaptation of the REF-scale. This self-applied scale consists of 34 items that evaluate the referential thinking in Likert format. We employed a longitudinal design (brief time-series). C Young (p < 0.01) was used for the statistical analysis of the data and the method of least squares to obtain the trend line. We included 103 measures registered at an interval of 3 days.

It's observed a significant declining trend in the whole of the measures both intensity and frequency from the beginning of therapy. However, we observed a significant declining trend in intensity but not in frequency when we analyzed the data from the 50th measurement, which was the period during which the patient got worse.

It's confirmed again that the REF-scale is a stable and reliable measure. It's able to detect changes in the patient's evolution of the referential thinking from the beginning of therapy. In addition, the REF-scale is sensitive detecting decompensations in patients. Therefore, we conclude REF scale is a useful measure for the subsequent decision-making therapeutic.