The Overt Behaviour Scale (OBS): a tool for measuring challenging behaviours following ABI in community settings

The Overt Behaviour Scale (OBS) was designed as a comprehensive measure of common challenging behaviours observed after acquired brain injury (ABI) in community settings. The OBS comprises 34 items in nine categories that measure aggression, inappropriate sexual behaviour, perseveration, wandering, inappropriate social behaviour and lack of initiation. The aim of the current study was to determine the reliability, validity and responsiveness of the OBS.

Two adult community-based samples of people with ABI were recruited. Sample 1 (n= 30) were concurrently evaluated on the OBS by two raters and again 1 week later to test stability. Other validating scales were also administered. Sample 2 (n= 28) were clients of the ABI Behaviour Consultancy who were treated for challenging behaviours and were administered the OBS before treatment commenced and then again 4 months later.

Inter-rater reliability and stability coefficients for the OBS total score was strong (0.97 and 0.77, respectively). Initial evidence of convergent and divergent validity was shown by the differential pattern of correlations with other measures. Moderate-to-strong coefficients (range 0.37-0.66) were observed between the OBS and other measures that had behavioural content (i.e. Mayo-Portland Adaptability Inventory, Current Behaviour Scale, Neurobehavioural Rating Scale-Revised). Divergent validity was shown by the lack of correlation between the OBS and the sub-scales of these tools that do not measure challenging behaviour. Finally, responsiveness was demonstrated with a significant decrease in OBS scores in the expected direction over the 4-month period. This improvement was confirmed by corroborating evidence from key informants.

The OBS shows promise as a reliable, valid and responsive measure that can be used for the systematic assessment of challenging behaviours in community settings.