Figure 3. Weighted Youden Index for Various FEV1:FVC Thresholds Across a Range of Relative Weights for Sensitivity and Specificity.
The weighted Youden index for the 0.70 threshold was higher than the lower limit of normal (LLN) threshold for weights of 0.35 or greater. Where weight equals 0.5, sensitivity and specificity are weighted equally. For each ratio threshold, the sensitivity and specificity were estimated from unadjusted Cox proportional hazards models including ratio thresholds only. Weight (x-axis) indicates relative weight assigned to sensitivity vs specificity. FEV1:FVC indicates the ratio of the forced expiratory volume in the first second to the forced vital capacity.