The Forensic Inpatient Observation Scale (FIOS): development, reliability and validity.

INTRODUCTION: Re-offending, as a measure of success in forensic psychiatry, gives no information about other behaviours that may have changed. The development of the Forensic Inpatient Observation Scale (FIOS), an observation instrument to assess the non-offending functioning of forensic patients, is described. STUDY 1: In the first study the development of the initial item pool of the FIOS is described. This resulted in an instrument consisting of 78 items and seven scales. The internal reliability of the scales ranged from 0.78 to 0.91. The inter-rater reliability of the scales varied from 0.50 to 0.85 and the test retest reliability over a period of three weeks was high for most scales, ranging from 0.74 to 0.89. STUDY 2: In the second study the FIOS was developed further in another sample of forensic patients. This time exploratory factor analysis with Varimax rotation and post hoc reliability analysis were applied to determine the factor structure among the items. This resulted in an item pool of 35 items, among which six factors could be distinguished that closely resemble the factor structure of the FIOS in study one: (1) self-care, (2) social behaviour, (3) oppositional behaviour, (4) insight offence/problems, (5) verbal skills and (6) distress. Most items have high loadings on the factor they are assigned; 29 items have a loading of 0.60 or higher. The internal consistency of the scales ranges from 0.73 to 0.91 and the scales appear to be measuring independent constructs. Twenty-five out of the 35 items have an inter-rater correspondence of 90% or higher and 30 out of 35 items have an inter-rater correspondence of 87.5% or higher. The inter-rater reliability on the scale level, however, was somewhat less satisfying with correlations ranging from 0.50 to 0.69. DISCUSSION: It is argued that training the observers on a more regular basis will improve the inter-rater reliability. There is some evidence for the convergent validity of the FIOS. The FIOS has some advantages over existing inpatient scales in that it is developed specifically for forensic patients, it does not particularly focus on axis 1 symptoms but includes oppositional behaviour and attitudes to offending.