Abbreviated quality of life scales for schizophrenia: comparison and utility of two brief community functioning measures.

BACKGROUND

The Heinrichs-Carpenter Quality of Life Scale (QLS) is the most extensively used real-world community functioning scale in schizophrenia research. However, the extensive time required to administer it and the inclusion of items that overlap conceptually with negative symptoms limit its use across studies. The present study examined the validity and utility of two abbreviated QLS measures against the full QLS excluding negative symptom items.

METHOD

The sample included 1427 patients with schizophrenia who completed the baseline visit in the CATIE study. The validity of two abbreviated QLS measures (7-item and 4-item) were examined with the full QLS, excluding the intrapsychic foundations subscale, using correlation analysis. The utility of the abbreviated measures was explored by examining associations between the functioning scales and clinical variables and longitudinal change.

RESULTS

Both abbreviated QLS measures were highly predictive of the full QLS (both r=0.91, p<0.001), with no difference in predictive value between the abridged measures. Functional status was significantly associated with symptoms and cognition. Importantly, the strength of these associations was similar between the abbreviated and full QLS. Finally, multiple regression models examining the explanatory power of amotivation/apathy in predicting functioning scores after other symptoms and neurocognition had been accounted for were essentially identical irrespective of the QLS instrument used as the dependent measure. Longitudinal change was also similar across the three scales.

CONCLUSIONS

The 7-item abbreviated QLS is recommended as a brief measure of community functioning for individuals with schizophrenia, especially when assessment of functional outcome is not the focus.