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. 2021 Jul 19;7(7):CD010772.
doi: 10.1002/14651858.CD010772.pub3.

Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) for the detection of dementia within a secondary care setting

Jennifer K Burton  1 , Patricia Fearon  2 , Anna H Noel-Storr  3 , Rupert McShane  4 , David J Stott  5 , Terry J Quinn  6
Affiliations

Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) for the detection of dementia within a secondary care setting

Jennifer K Burton et al. Cochrane Database Syst Rev. .

Abstract

Background: The diagnosis of dementia relies on the presence of new-onset cognitive impairment affecting an individual's functioning and activities of daily living. The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) is a questionnaire instrument, completed by a suitable 'informant' who knows the patient well, designed to assess change in functional performance secondary to cognitive change; it is used as a tool for identifying those who may have dementia. In secondary care there are two specific instances where patients may be assessed for the presence of dementia. These are in the general acute hospital setting, where opportunistic screening may be undertaken, or in specialist memory services where individuals have been referred due to perceived cognitive problems. To ensure an instrument is suitable for diagnostic use in these settings, its test accuracy must be established.

Objectives: To determine the accuracy of the informant-based questionnaire IQCODE for detection of dementia in a secondary care setting.

Search methods: We searched the following sources on the 28th of January 2013: ALOIS (Cochrane Dementia and Cognitive Improvement Group), MEDLINE (Ovid SP), EMBASE (Ovid SP), PsycINFO (Ovid SP), BIOSIS Previews (Thomson Reuters Web of Science), Web of Science Core Collection (includes Conference Proceedings Citation Index) (Thomson Reuters Web of Science), CINAHL (EBSCOhost) and LILACS (BIREME). We also searched sources specific to diagnostic test accuracy: MEDION (Universities of Maastricht and Leuven); DARE (Database of Abstracts of Reviews of Effects - via the Cochrane Library); HTA Database (Health Technology Assessment Database via the Cochrane Library) and ARIF (Birmingham University). We also checked reference lists of relevant studies and reviews, used searches of known relevant studies in PubMed to track related articles, and contacted research groups conducting work on IQCODE for dementia diagnosis to try to find additional studies. We developed a sensitive search strategy; search terms were designed to cover key concepts using several different approaches run in parallel and included terms relating to cognitive tests, cognitive screening and dementia. We used standardised database subject headings such as MeSH terms (in MEDLINE) and other standardised headings (controlled vocabulary) in other databases, as appropriate.

Selection criteria: We selected those studies performed in secondary-care settings, which included (not necessarily exclusively) IQCODE to assess for the presence of dementia and where dementia diagnosis was confirmed with clinical assessment. For the 'secondary care' setting we included all studies which assessed patients in hospital (e.g. acute unscheduled admissions, referrals to specialist geriatric assessment services etc.) and those referred for specialist 'memory' assessment, typically in psychogeriatric services.

Data collection and analysis: We screened all titles generated by electronic database searches, and reviewed abstracts of all potentially relevant studies. Two independent assessors checked full papers for eligibility and extracted data. We determined quality assessment (risk of bias and applicability) using the QUADAS-2 tool, and reporting quality using the STARD tool.

Main results: 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.

Authors' conclusions: 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.

PubMed Disclaimer

Conflict of interest statement

JKH ‐ None known.

PF ‐ None known.

ANS ‐ None known.

DJS ‐ None known.

RMcS ‐ None known.

TJQ ‐ None known.

Figures

1
1
Study flow diagram.
2
2
Risk of bias and applicability concerns summary: review authors' judgements about each domain for each included study
3
3
Summary ROC Plot, IQCODE using a 3.3 threshold score or nearest. The dark point is a summary point, the broken line represents 95% confidence region
4
4
Summary ROC Plot of IQCODE 3.3 threshold or nearest, comparing short form (16 item) and traditional IQCODE. The dark point is a summary point, the broken line represents 95% confidence region
5
5
Summary ROC Plot of pooled IQCODE data at a 3.3 threshold (or nearest value), with language as covariate. The dark point is a summary point, the broken line represents 95% confidence region
6
6
Summary ROC Plot of pooled IQCODE data at a 3.3 threshold (or nearest value), with setting as covariate. The dark point is a summary point, the broken line represents 95% confidence region
1
1. Test
All studies IQCODE 3.3 or closest
2
2. Test
All 16‐item IQCODE
3
3. Test
All 26‐item IQCODE
4
4. Test
IQCODE 3.3 Threshold
5
5. Test
IQCODE 3.4 Threshold
6
6. Test
IQCODE 3.5 Threshold
7
7. Test
IQCODE 3.6 Threshold
8
8. Test
IQCODE >3.6 Threshold
9
9. Test
16‐item IQCODE 3.3 Threshold
10
10. Test
16‐item IQCODE 3.4 Threshold
11
11. Test
16‐item IQCODE 3.5 Threshold
12
12. Test
16‐item IQCODE 3.6 Threshold
13
13. Test
26‐item IQCODE 3.3 Threshold
14
14. Test
26‐item IQCODE 3.4 Threshold
15
15. Test
26‐item IQCODE 3.6 Threshold
16
16. Test
Sensitivity analysis removing Goncalves
17
17. Test
Sensitivity analysis removing low average age
See this image and copyright information in PMC

Update of

References

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References to other published versions of this review

Quinn 2013
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