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Measurement of Agitation


The Agitated Behavior Scale (ABS; Corrigan, 1989) was developed to assess the nature and extent of agitation during the acute phase of recovery from acquired brain injury. Its primary purpose is to allow serial assessment of agitation by treatment professionals who want objective feedback about the course of a patient's agitation. Serial assessments are particularly important when treatment interventions are being attempted. The ABS has been used in multiple intervention studies across a variety of populations, including persons with brain injury, Alzheimer's dementia, schizophrenia, and bipolar disorder, and patients receiving emergency medical transport (Tabloski et al.,1995; Meehan et al., 2001; Beaulieu, et al., 2008; Allen et al., 2011; Weiss et al., 2011). Corrigan et al. (1996) demonstrated the utility of the ABS for measuring agitation in nursing home residents with progressive dementias, primarily Alzheimer's disease. 

Reliability of the ABS

The initial validation studies (Corrigan, 1989) showed correlations between ratings conducted on the same day that exceeded .70 for the Total score (subscale scores were not available at that time). Inter-rater reliability was re-examined (Bogner et al., 1999) due to the instrument’s increased use with different populations, rated by individuals from various disciplines, based on a variety of observation periods. With a sample of persons receiving acute rehabilitation for acquired brain injury, research assistants (psychology interns and a rehabilitation nurse) rated behavior based on 10-minute observation periods. The research assistants’ ratings yielded a correlation coefficient for the Total score of .92. The correlation coefficients for the factors Disinhibition, Aggression, and Lability were .90, .91, and .73, respectively. The reliability of the Lability score was likely reduced by the small number of items used in its calculation. When comparisons were made between the ratings made of the research assistants based on 10-minute observation periods and the ratings made by nurses based on an 8-hour shift, the correlation coefficients for the Total and subscale scores were much lower (.36 to .60). The lower correlation was likely due to different behaviors being measured in the varied conditions and time intervals. Agitation has been known to change in intensity throughout the day, and in response to the regulation of stimulation. When serial monitoring is the goal, it is important that comparisons be made under comparable conditions.

Inter-rater reliability was also examined with a sample of individuals residing in a long-term care facility whose primary diagnosis was dementia. Research assistants completed the ratings based on 10-minute observation periods. The correlation coefficient for the Total score was .91, while the coefficients for the factor scores were .87 for Disinhibition, .89 for Aggression, and .86 for Lability.

Examination of the internal consistency of the scale found Cronbach's alphas ranging from .83 to .92 in the original validation study (Corrigan, 1989). With the two samples examined by Bogner et al (1999), Cronbach’s alphas ranged from .74 to .92. A subsequent study using rating scale analysis yielded a person separation reliability statistic of .81 for the Total score (Bogner et al., 2000). The relatively high internal consistency of the scale suggests that agitation, as measured by the ABS, is a unitary construct, with three facets being individually prominent at times.

Validity

The original development of the ABS demonstrated the content validity of items and concurrent validity of the Total Score. Subsequent studies have shown the ABS scores to be associated with change in cognitive status (Corrigan & Mysiw, 1988; Nott et al., 2010) and able to differentiate confusion and inattention (Corrigan & Mysiw, 1988; Corrigan et al., 1992). Construct validity has been further substantiated by the identification of underlying factors (Corrigan & Bogner, 1994) and through rating scale analysis (Bogner et al., 2000). The factor and rating scale analyses indicated that agitation is represented by one general construct with three underlying, correlated factors: Aggression, Disinhibition, and Lability. While the Total Score is the best measure of agitation, the subscale scores may provide important additional clinical and research data. The Total Score and three underlying subscales have proven stable over multiple samples (Corrigan & Bogner, 1994; Corrigan et al., 1996).

Next: Administration and Use of the Agitated Behavior Scale (ABS)

This website has been funded with financial assistance from Grant #H133A120086 awarded by the U.S. Department of Education, National Institute on Disability Rehabilitation Research (NIDRR) to the Ohio Valley Center for Brain Injury Prevention and Rehabilitation for the current funding period of 10/01/2012 - 09/30/2017.