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A structured collateral interview regarding cognition and function (the IQCODE) for assessment of possible dementia

Quinn TJ, Fearon P, Noel-Storr AH, Young C, McShane R, Stott DJ
Published Online: 
10 April 2014

Numbers of people with dementia and other cognitive problems are increasing globally. Early diagnosis of dementia is recommended but there is no agreement on the best approach or how non-memory specialists should assess patients. A potential strategy is to interview friends or family of the subject to assess for change in function or cognition. Various methods of this collateral interview are available and the most commonly used is the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE). We searched differing databases of published research for all papers relating to the accuracy of IQCODE for selecting those with dementia. We found eleven studies that tested diagnostic accuracy of IQCODE in community dwelling individuals, we were able to combine their findings to give a summary result. We compared two forms of IQCODE questionnaire and found that a short form with fewer questions was just as accurate as the original longer questionnaire. The overall accuracy of IQCODE was reasonable although not perfect. If IQCODE were to be used on its own for assessing large populations of older adults, it would label many people with dementia who do not have the disease and also miss the diagnosis in a substantial proportion.