An informant interview for the diagnosis of dementia and depression in older adults (IDD-GMS)

Background. There has been no instrument developed for the differential diagnosis of psychiatric conditions using an informant. The present study describes the development and validation of an informant interview for the diagnosis of dementia and depression in older adults (IDD-GMS). The IDD-GMS, as its name indicates, is based upon the well-established Geriatric Mental State Schedule (GMS). Method. Thirty older adults with psychiatric illnesses were identified. An informant/carer was interviewed using the IDD-GMS. Questions from the GMS were altered to reflect the informant nature of the interview. Validity was compared to ICD-10 diagnoses. Interrater reliability was determined. Results. Using a hierarchical diagnostic system, receiver operating characteristics demonstrated one optimal cutpoint for sensitivity, >13 for dementia and >16 for depression, and one for specificity, >13 for dementia and >10 for depression. Conclusion. The validity and reliability of the IDD-GMS falls within acceptable limits and indicates that the IDD-GMS can be used as a diagnostic instrument for dementia and depression. The IDD-GMS represents the first informant interview to achieve this. (C) 1998 John Wiley & Sons, Ltd.