Diagnostic accuracy of the overlapping infinity loops, wire cube, and clock drawing tests in subjective cognitive impairment, mild cognitive impairment and dementia

Background

It is increasingly important to establish screening tests for early cognitive decline. Figure drawing tasks are commonly used as part of broader cognitive screening tests. The aim of this study was to determine the diagnostic accuracy of three commonly used figure drawing tasks (overlapping infinity loops, wire cube and clock drawing task (CDT)) in participants with subjective cognitive decline (SCD), mild cognitive impairment (MCI) and dementia. The figure drawing tasks have only been assessed once before in MCI, and never before in SCD.

Method

Participants with cognitive symptoms were recruited from the Tasmanian ISLAND cognitive clinic and healthy controls were recruited from a community sample. All participants completed the Addenbrooke’s Cognitive Examination III which includes the three figure drawing tasks. Clinic patients were categorised according to interdisciplinary consensus diagnosis. Area under ROC curves were calculated to determine the discriminatory ability of each drawing task.

Results

112 adults were recruited; 51 had normal cognition (NC), 21 SCD, 24 MCI and 16 dementia. The CDT was the most discriminatory between NC and dementia (AUC 0.77; p<0.01), and between MCI and dementia (AUC 0.76; p<0.01). The wire cube also discriminated between NC and dementia (AUC 0.7; p<0.05). None of the three tasks discriminated MCI from NC, or SCD from NC.

Discussion/Conclusion

The CDT was the most discriminatory test, followed by the wire cube. This may help guide clinicians who often choose just one figure drawing task due to time constraints or patient fatigue. The infinity loops were not able to discriminate between any of the groups, which casts some doubt on their usefulness as a screening tool. Further studies are required to replicate these findings.