Which figure copy test is more sensitive for cognitive impairment in Parkinson's disease: Wire cube or interlocking pentagons?

Background: Performance on figure copy tests has been shown to predict progressive cognitive decline in Parkinson's disease (PD). Historically, the interlocking pentagons from the Mini Mental State Exam (MMSE) have been the figure copy test most commonly used during cognitive screening evaluations. However, the wire cube from the Montreal Cognitive Assessment (MoCA) is increasingly being used. Objective To evaluate which of these figure copy tests is more sensitive for cognitive impairment in PD.

Methods: Sixty-three PD patients from UK and USA completed the MMSE and MoCA. Logistic regression and sensitivity/specificity analyses were used to evaluate the utility of each figure copy test for detecting global cognitive impairment.

Results: The wire cube was a significant indicator of cognitive impairment (OR = 4.79, 95% CI = 1.63-14.07, p = 0.004), with a sensitivity/specificity of 0.74/0.63 in our sample. In contrast, interlocking pentagons were not a significant indicator of cognitive impairment (OR = 1.88, 95% CI = 0.54-6.50, p = 0.32), with a sensitivity/specificity of 0.26/0.84.

Conclusion: The wire cube is more sensitive to cognitive impairment in PD, most likely related to its greater complexity. The results have implications for clinicians who may have time for just one figure copying task as part of a brief screen for cognitive impairment in busy clinics and for researchers applying the PD mild cognitive impairment diagnostic criteria necessitating two tests of visuospatial function to be administered.