Summary of findings 3. New Summary of findings table.
| What is the accuracy of the Informant Questionnaire for Cognitive Decline in the Elderly (IQCODE) test for detection of dementia using different versions of IQCODE and using different languages of administration | |||||
| Population | Adults attending secondary care services, with no restrictions on the case‐mix of recruited participants | ||||
| Setting | Our primary setting of interest was secondary care, within this rubric we included inpatient wards and hospital outpatient clinics. Secondary care settings can be considered as two groups: (1) Studies conducted in a specialist memory/psychogeriatrics setting where participants were referred due to cognitive symptoms (2) Non‐memory focused hospital services. These included unselected admissions of older adults, those referred to specialist older people's assessment teams, outpatient attenders and inpatients under the care of geriatricians |
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| Index test | Informant Questionnaire for Cognitive Decline in the Elderly (IQCODE) administered to a relevant informant. We restricted analyses to the traditional 26‐item IQCODE and the commonly used short form IQCODE with 16 items | ||||
| Reference Standard | Clinical diagnosis of dementia made using any recognised classification system | ||||
| Studies | Cross‐sectional studies were included, we did not include case‐control studies | ||||
| Comparative analyses | |||||
| Test | No. of participants (studies) | Dementia prevalence total across studies | Findings | Implications | |
| 26‐item versus 16‐item IQCODE | Total: n = 2745 (13) 26 item n = 977 (6) |
Total n = 1413 (51%) 26 item n = 514 (53%) 16 item n = 899 (51%) |
No significant difference in test accuracy Relative sensitivity of 26‐item versus 16‐item IQCODE: 0.98 (95% CI 0.89 to 1.07) Relative specificity of 26‐item versus 16‐item IQCODE: 0.99 (95% CI 0.75 to 1.33) |
There was no difference in accuracy between IQCODE versions so it may be justifiable to advocate use of the short form to minimise responses required | |
| English language versus Non‐English | Total: n = 2745 (13) English language n = 1216 (6) |
Total n = 1413 (51%) English language n = 759 (62%) Non‐English language n = 654 (43%) |
No significant difference in test accuracy
Relative sensitivity of English language versus non‐English language IQCODE: 1.07 (95% CI 0.98 to 1.17) Relative specificity of English language versus non‐English language IQCODE: 1.10 (95% CI 0.83 to 1.47) |
The language of administration does not significantly influence the diagnostic accuracy of IQCODE | |
| Non‐memory setting versus memory | Total: n = 1918 (9)* memory setting n = 1352 (6) |
Total n = 1129 (59%) memory setting n = 984 (73%) non‐memory setting n = 145 (26%) |
Significant difference in test accuracy between settings (P = 0.019), due to higher specificity in non‐memory settings
Relative sensitivity of non‐memory versus memory IQCODE: 1.06 (95% CI 0.99 to 1.15) Relative specificity of non‐memory versus memory IQCODE: 1.49 (1.22 to 1.83) |
The lower level of specificity in the specialist memory services is of limited clinical concern as other tests will be used in this setting and incorrectly diagnosing someone with dementia based on IQCODE alone would be unlikely. In the non‐memory setting it is likely a positive IQCODE would prompt referral to specialist services, and this may be associated with psychological harm and unnecessary expense. Applying our non‐memory findings to the UK; there are around 2 million unscheduled admissions annually in over‐65s (Imison 2012) and a dementia prevalence of 42.4% in this group (Sampson 2009). Using the IQCODE alone to screen for dementia would result in 42,400 people with dementia not being identified and 218,880 dementia‐free people being referred inappropriately for specialist assessment. |
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| CAUTION: The results in this table should not be interpreted in isolation from the results of the individual included studies contributing to each summary test accuracy measure. These are reported in the main body of the text of the review. *: Four studies included participants recruited in both specialist memory and non‐memory settings, without reporting outcome data stratified by recruitment setting and are thus not included in the quantitative synthesis | |||||