Development of the QoL.BD: a disorder-specific scale to assess quality of life in bipolar disorder.

BACKGROUND

There is wide recognition that symptom ratings alone are inadequate to measure outcomes in bipolar disorder (BD), and quality of life (QoL) has been proposed as an important separable construct. Although a literature on QoL in BD exists, there is no disorder-specific measure of QoL in BD. In 2004, we embarked upon a four-year mixed-method program of research to develop such a measure that could function as an outcome tool in clinical trials of pharmacological or psychosocial treatment interventions, longitudinal monitoring, or routine clinical care.

METHODS

The project was informed by standard protocols for the development of disorder-specific QoL measures. Two phases of scale development were pursued across four empirical studies. Item generation involved a qualitative investigation of individuals with BD, family members, and field experts (Study 1), as well as a literature review. Item reduction analyses were conducted using an intensive small-N design with affected individuals (Study 2), a large field sample (Study 3), and a final small-N item reduction study, again involving individuals with the disorder and field experts (Study 4).

RESULTS

Initial field testing of the Quality of Life in Bipolar Disorder (QoL.BD) scale supports use of the instrument as a feasible, reliable and valid disorder-specific QoL measure for BD. Internal reliability of the QoL.BD is impressive, test-retest reliability is appropriate, and the direction and magnitude of correlations with external measures are as expected. As a new instrument, the QoL.BD must be compared against existing options for measuring QoL in this population. Significantly, data suggest that the greater specificity of the QoL.BD relative to the Quality of Life Enjoyment and Satisfaction Questionnaire renders the new instrument more sensitive to clinical change in BD.

CONCLUSIONS

Quality of life scales can provide important information additional to that provided by traditional assessments of outcome in BD. Our intensive, mixed-method development of the QoL.BD has produced a useful additional measure of well-being for this complex and often disabling condition.