Abstract: From 72 papers describing IQCODE test accuracy, we included 13 papers, representing data from 2745 individuals (n = 1413 (51%) with dementia). Pooled analysis of all studies using data presented closest to a cut-off of 3.3 indicated that sensitivity was 0.91 (95% CI 0.86 to 0.94); specificity 0.66 (95% CI 0.56 to 0.75); the positive likelihood ratio was 2.7 (95% CI 2.0 to 3.6) and the negative likelihood ratio was 0.14 (95% CI 0.09 to 0.22). There was a statistically significant difference in test accuracy between the general hospital setting and the specialist memory setting (P = 0.019), suggesting that IQCODE performs better in a 'general' setting. We found no significant differences in the test accuracy of the short (16-item) versus the 26-item IQCODE, or in the language of administration. There was significant heterogeneity in the included studies, including a highly varied prevalence of dementia (10.5% to 87.4%). Across the included papers there was substantial potential for bias, particularly around sampling of included participants and selection criteria, which may limit generalisability. There was also evidence of suboptimal reporting, particularly around disease severity and handling indeterminate results, which are important if considering use in clinical practice. The IQCODE can be used to identify older adults in the general hospital setting who are at risk of dementia and require specialist assessment; it is useful specifically for ruling out those without evidence of cognitive decline. The language of administration did not affect test accuracy, which supports the cross-cultural use of the tool. These findings are qualified by the significant heterogeneity, the potential for bias and suboptimal reporting found in the included studies.

Plain-language summary: We searched electronic databases of published research studies, looking for all studies of IQCODE in a hospital setting. We searched from the first available papers in scientific databases up to and including January 2013. We found 13 relevant studies which had results suitable to be combined in a single analysis. Of these papers, six (1352 participants) described studies conducted in “specialist” services such as memory clinics or wards. Three papers (566 participants) described studies conducted in general older adult services and four studies (827 participants) included both specialist and general services. Summarising the available papers, we found that IQCODE was useful for 'ruling out' possible dementia in the general hospital setting. This means if a person has a low score on IQCODE testing they probably do not have dementia. IQCODE was less useful in specialist memory clinics and psychiatry wards. We also found that a short version of the IQCODE gave similar results to the traditional longer version. As part of our assessment we looked at whether the design of the available studies was suitable for the study question. We found several instances where the design of the study could be improved. For example, seven of the thirteen studies only included a selection of all the people attending the service who could have been assessed with IQCODE. We also looked at how well researchers reported the conduct and results of their studies. Again, there were many instances where the reporting could be improved. A common issue was not describing the severity of memory and thinking problems in those thought to have dementia, only reported in three of the included studies. In summary, IQCODE may be a useful tool for assessing adults for possible dementia. There are still a number of unanswered questions around how useful IQCODE may be in hospital settings. For example, before we start using IQCODE routinely we need to describe if it is practical and acceptable to hospital staff, to patients and to their carers. The review was performed by a team based in research centres in the UK (Glasgow, Leicester, Oxford). We had no external funding specific to this study and we have no conflicts of interest that may have influenced our assessment of the research data.