Table 2.

First-stage operating characteristics for IQCODE cutoffs in discovery and confirmatory samples separately and combined

Cutoff	Sensitivity	Specificity	PPV	NPV	Efficiency
Discovery sample
≥3.1	0.86 (0.77, 0.92)	0.68 (0.61, 0.74)	0.57 (0.48, 0.65)	0.91 (0.85, 0.95)	0.50 (0.44, 0.56)
≥3.2	0.82 (0.72, 0.89)	0.83 (0.76, 0.88)	0.70 (0.60, 0.78)	0.90 (0.85, 0.94)	0.39 (0.33, 0.44)
≥3.3	0.72 (0.62, 0.81)	0.88 (0.82, 0.92)	0.74 (0.64, 0.83)	0.86 (0.81, 0.91)	0.32 (0.27, 0.38)
≥3.4	0.56 (0.45, 0.66)	0.92 (0.87, 0.95)	0.78 (0.66, 0.87)	0.81 (0.75, 0.86)	0.24 (0.19, 0.29)
Confirmatory sample
≥3.1	0.87 (0.78, 0.93)	0.65 (0.57, 0.71)	0.54 (0.46, 0.63)	0.91 (0.85, 0.95)	0.52 (0.44, 0.56)
≥3.2	0.78 (0.68, 0.86)	0.82 (0.76, 0.87)	0.68 (0.58, 0.77)	0.89 (0.83, 0.93)	0.38 (0.32, 0.44)
≥3.3	0.70 (0.59, 0.79)	0.90 (0.85, 0.94)	0.78 (0.68, 0.86)	0.86 (0.80, 0.90)	0.29 (0.24, 0.35)
≥3.4	0.64 (0.53, 0.74)	0.94 (0.90, 0.97)	0.84 (0.74, 0.92)	0.84 (0.79, 0.89)	0.25 (0.20, 0.30)
Combined sample
≥3.2	0.80 (0.74, 0.86)	0.82 (0.78, 0.86)	0.69 (0.62, 0.75)	0.89 (0.86, 0.92)	0.38 (0.34, 0.42)

Abbreviations: IQCODE, Informant Questionnaire on Cognitive Decline in the Elderly; PPV, positive predictive value; NPV, negative predictive value.

NOTE. Efficiency is the proportion of patients who undergo second-stage testing.