A pilot study to validate modification of the Duke University Severity of Illness scale to measure a family's burden of illness
Background. Measurement of burden of illness is rarely undertaken in general practice, although a specific tool [Duke University Severity of Illness DUSOI scale] has been incorporated in the International Classification in Primary Care. This measures the burden of illness in an individual at a point in time. There has not been any measure of the burden of illness in families. Such an instrument would allow measurement of the impact of events on the health of families. Objective. This pilot study aimed to modify the DUSOI to measure a family's burden of illness and to validate any changes. Methods. The DUSOI was modified to measure the mean burden of illness in a family over a 1 year period. The changes were then subject to a validation process using convenient samples of patients from the author's multidoctor practice in Australia. Reliability was examined by the test-re-test method. Inter-rater reliability could not be assessed. Responsiveness was measured by measuring changes in score in the years before and after four events: counselling for a minor mental health problem; referral to a psychiatrist; diagnosis and treatment of breast cancer; and the occurrence of an acute myocardial infarction. Results. The modifications made to the DUSOI have not altered the face or content validity of the original instrument. Construct validity and test-re-test reliability were satisfactory. Interrater reliability was not tested, but the original single patient score showed levels lower than are desirable. Responsiveness varied significantly. Families where a member was referred to a psychiatrist showed a decrease in burden after referral, while families where a member suffered an infarct showed a large increase. The other family groups did not show any change. Conclusion. A Family DUSOI will be of value in research when validated for individual conditions.