The IQCODE: Using informant reports to assess cognitive change in the clinic and in older individuals living in the community

The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) uses the report of an informant to assess an individual's change in cognition in the last 10 years. Unlike cognitive screening tests administered at one point in time, it is unaffected by pre-morbid cognitive ability or by level of education. When used as a screening test for dementia, the IQCODE performs as well as the Mini-Mental State Examination (MMSE), which is the most widely used cognitive screening instrument. Other evidence of validity comes from correlations with change in cognitive test scores and associations with neuropathological and neuroimaging changes. The main limitation of the IQCODE is that it can be affected by the informant's emotional state. The IQCODE is suitable for use as a screening test in clinical settings, for retrospective cognitive assessment where direct data are not available, and for assessment in large-scale epidemiological studies. Versions are available in many languages.