Development and preliminary testing of the General 5-Spectrum Measure (GSM-V)

The Collaborative Spectrum Project has developed structured interviews and self-report instruments to assess the spectrum of symptomatology related to panic-agoraphobia, mood, social phobia, and obsessive-compulsive and eating disorders. In order to obtain a rapid pre-test on all five of these spectrum conditions, the authors sought to develop a brief instrument that would tap these conditions. This paper reports on 1) the procedures to derive this composite instrument, the General 5-Spectrum Measure (GSM-V), by selecting items from five existing spectrum instruments, and 2) preliminary testing of the internal consistency and test-retest reliability of the GSM-V. The GSM-V consists of 54 items grouped into scales that explore the five spectra described above. It was derived from existing data on five Structured Clinical Interviews that were designed to assess spectrum features by using multiple regression models. The GSM-V was administered as a stand-alone instrument along with the self-report versions of the spectrum interviews to a sample of 56 psychiatric patients in order to determine the internal consistency of its scales and the correlation with the parent spectrum measures. Moreover, to determine whether subjects would respond consistently to the same items on two different occasions (test-retest reliability), the GSM-V was re-administered within 1 month from the baseline. From each of the five spectrum interviews, items were selected that accounted for a significant proportion of variance of the total score of the parent instrument. The five sets of items so selected constitute separate scales. The scales of the GSM-V had a good to excellent internal consistency, excellent test-retest reliability, and proved to reproduce adequately the long-form measures. The GSM-V appears to provide a reliable alternative to the five longer spectrum interviews. It is envisaged that the instrument will be most useful as a pre-test to identify subjects with spectrum features that should be explored in greater detail. Additionally, it could provide a better characterization of patients with a syndromal level Axis-I disorder, who might require specific treatment strategies targeted to co-occurring subsyndromal conditions.