Summary of findings 2. 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 when differing thresholds are used to define IQCODE positive cases | |||||
| 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 | ||||
| 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 | We included cross‐sectional studies but not case‐control studies | ||||
| Test |
Summary accuracy (95% CI) |
No. of participants (studies) |
Dementia prevalence |
Implications, Quality and Comments | |
| IQCODE cut‐off 3.3 or nearest | sens: 0.91 (95% CI 0.86 to 0.94); spec: 0.66 (95% CI 0.56 to 0.75) +ve LR: 2.7 (95% CI 2.0 to 3.6) ‐ve LR: 0.14 (95% CI 0.09 to 0.22) |
n = 2745 (13 studies) | n = 1413 (51%) | Within the range of commonly used cut‐offs for defining IQCODE positivity, there is no clearly optimal value for use in secondary care settings. The sensitivity falls as the diagnostic threshold increases from 3.3‐3.6, with a relative increase in the specificity. The preferred balance between sensitivity and specificity is debatable. Both false positive (person diagnosed with possible dementia and referred for further assessment) and false negative (person with dementia has diagnosis missed and is not referred to specialist services) are associated with potential harms. The dementia prevalence was highly varied in included studies (10.5% to 87.4%) reflecting the heterogeneity of included participants within a "hospital" setting. This heterogeneity and associated "modelling" of real world implications of the test accuracy data presented are described in the next summary of findings table. |
|
| IQCODE cut‐off 3.3 | sens: 0.96 (95% CI 0.94 to 0.98) spec: 0.66 (95% CI 0.41 to 0.84) +ve LR: 2.8 (95% CI 1.5 to 5.5) ‐ve LR: 0.1 (95% CI 0.03 to 0.1) |
n = 722 (4 studies) | n = 334 (46%) | ||
| IQCODE cut‐off 3.4 | sens: 0.94 (95% CI 0.84 to 0.98) spec: 0.73 (95% CI 0.59 to 0.85) +ve LR: 3.5 (95% CI 2.1 to 5.8) ‐ve LR 0.1 (95% CI 0.03 to 0.2) |
n = 1211 (4 studies) | n = 394 (33%) | ||
| IQCODE cut‐off 3.5 | sens: 0.92** spec: 0.63** |
n = 269 (1 study) | n = 152 (57%) | ||
| IQCODE cut‐off 3.6 | sens: 0.89 (95% CI 0.85 to 0.92) spec: 0.68 (95% CI 0.56 to 0.79) +ve LR: 2.8 (95% CI 1.9 to 4.0) ‐ve LR: 0.2 (95% CI 0.1 to 0.2) |
n = 1576 (9 studies) | n = 968 (61%) | ||
| 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. **: quantitative synthesis not performed as only one study reported data at cut‐off of 3.5 | |||||
Abbreviations: sens ‐ sensitivity; spec ‐ specificity; +ve LR ‐ positive likelihood ratio; ‐ve LR ‐ negative likelihood ratio