Validating the MoCA for screening 3 77 The “optimum” cut-off scores against NoCI as calculated by the Younden index were <25 for detecting MCI ,sensitivity 88% (95%CI:81-92), specificity 49% (95%CI:44-53); <23 for CI, sensitivity 75% (95%CI:69-81), specificity 68% (95%CI:63-72); and <21 for MD, sensitivity 90% (95%CI:81-95), specificity 78% (95%CI:74-81) and comparable to literature (Lee et al., 2008; Memõria et al., 2013; Gil et al., 2015; Carson, Leach and Murphy, 2018; Pugh et al., 2018). The Positive Predictive value (PPV) and Negative Predictive value (NPV) were calculated (table 4) for the two scores with the highest computed Younden index. The PPV and the NPV show different results. The PPV was low in almost all situations whereas the NPV was high in all situations. Using a cut-off of <21 for dementia results in 31% of a positive MoCA having MD and 98% of a negative test having no MD. For detecting MCI at a cut-off of <26; 33% has indeed MCI when the MoCA is positive and 94% above this threshold will not have MCI. Table 4: Positive and Negative predictive values of cut-off scores with the highest Younden index Cut-off value† No Dem MCI NoCI PPV NPV PPV NPV PPV NPV % % % % % % Dem 20 35 97 62 87 44 96 95%CI (28-42) (94-98) (52-72) (79-92) (36-53) (93-97) 21 31 98 56 92 42 98 95%CI (26-38) (96-99) (47-65) (84-96) (34-49) (96-99) CI 23 54 84 95%CI (49-60) (80-88) 24 51 88 95%CI (46-56) (83-91) MCI 25 36 92 95%CI (31-41) (88-95) 26 33 94 95%CI (29-38) (90-97) † (MoCA-D below score) Dem: Dementia (n=81); MCI: Mild Cognitive impairment (n=153); NoCI: Referred patients no Cognitive Impairment (n=459); HC: Healthy Controls (n=84); CI; Cognitive Impairment (Dem + MCI; n=234). PPV: Positive Predictive Value. NPV: Negative Predictive Value. 95%CI: 95% Confidence Intervals.
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