Deriving a Mental Health Outcome Measure Using the Pooled Index: An Application to Psychiatric Consumer–survivors in Different Housing Types
Health Services and Outcomes Research Methodology
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Objective: We demonstrate the combination of several source measures into a comprehensive pooled index (PI) that measures functioning at a single point in time as well as improvement or worsening in functioning over time, and illustrate how this measure can be used to compare functioning in psychiatric clients living in three different housing types.
Methods: One hundred and forty-eight clients (55% women, mean age 45 yr.) were administered comprehensive interviews at two times one year apart. Four variables measured at both times were combined into a PI: three subscale scores from the Colorado Client Assessment Record, and the Quality of Life score from the Lehman interview. The PI was calculated for the initial interview, and between the two interviews to measure change in functioning over time (ΔPI).
Results: The greatest improvements in ΔPI scores occurred in those living independently, very slight worsening was seen among those in subsidized housing, and considerable worsening occurred among those in shelters. Regression results showed that living in a shelter, being older, PI at Year 1, being non-compliant with medications, duration of symptoms, and having more than 1 undesirable move in the past 2 years were independently associated with worsening in overall functioning over one year.
Conclusion: A pooled index change score, calculated from existing scale scores, provides a single dependent variable that quantifies the improvement or worsening of the overall functioning of psychiatric clients living in different housing types over time. A pooled index is one method of reducing multiple outcomes for analysis.