Accuracy of Two Cognitive Screening Tools to Detect Mild Cognitive Impairment in Parkinson's Disease

Abstract

Background: Patients with Parkinson's disease (PD) who have mild cognitive impairment (PD-MCI) are at increased risk of developing PD dementia (PDD). Therefore, it is important to identify PD-MCI in a reliable way.

Objectives: We evaluated the accuracy of the Parkinson's Disease-Cognitive Rating Scale (PD-CRS) and the Mattis Dementia Rating Scale-2 (MDRS-2) for detecting PD-MCI. Data from healthy subjects were used to correct for demographic influences.

Methods: We compared the accuracy of the two instruments using ROC analysis. The gold standard was level II diagnosis of PD-MCI according to consensus criteria of the International Parkinson and Movement Disorder Society.

Results: Seventy-five healthy subjects and 125 PD patients were included. Education level, age and sex correlated with the PD-CRS, but only age correlated with the MDRS-2. Twenty-seven percent of the patients had PD-MCI. Areas under the curve (AUCs) for raw scores of PD-CRS and MDRS-2 were 0.83 and 0.81, respectively. At the optimal cut-off for the PD-CRS (101/102), sensitivity was 88% and specificity was 64%. For the MDRS-2 (139/140) sensitivity and specificity were 68% and 79%, respectively.AUCs for demographically corrected scores of PD-CRS and for age-corrected scores of MDRS-2 were 0.80 and 0.78, respectively. At the optimal cut-off for the PD-CRS, sensitivity was 79% and specificity was 72%, while for the MDRS-2 these were 77% and 67%, respectively.

Conclusions: Both cognitive screening tools are suitable for distinguishing PD-MCI patients from cognitively intact PD patients. Demographical correction of scores did not improve sensitivity and specificity.

Keywords: Parkinson's Disease‐Cognitive Rating Scale; cognitive screening, Mattis Dementia Rating Scale‐2; mild cognitive impairment, Parkinson's disease.

Figure 1

(A) Distributions of raw PD‐CRS scores in cognitively intact PD patients, PD‐MCI patients, and healthy controls. (B) Distributions of raw MDRS‐2 scores in cognitively intact PD patients, PD‐MCI patients, and healthy controls. Abbreviations: HC, healthy control subjects; MDRS‐2, Mattis Dementia Rating Scale‐2; PD‐CogInt, cognitively intact PD patients; PD‐CRS, Parkinson's Disease‐Cognitive Rating Scale; PD‐MCI, PD patients with mild cognitive impairment.

Figure 2

Scatterplot of raw scores of MDRS‐2 and PD‐CRS in cognitively intact PD patients, PD‐MCI patients, and healthy control subjects. Continuous line: regression line describing the relation between both scales (R² = 0.39); dashed lines: 90% individual confidence interval. Abbreviations: HC, healthy control subjects; MDRS‐2, Mattis Dementia Rating Scale‐2; PD‐CogInt, cognitively intact PD patients; PD‐CRS, Parkinson's Disease‐Cognitive Rating Scale; PD‐MCI, PD patients with mild cognitive impairment.