3. A total of 72 subjects were tested for birch pollen allergy with a prick diagnostic kit, and 77 subjects were tested for Fraxinus pollen allergy, also with a prick diagnostic kit. The diagnostic test results are given as the diameter of wind mass (mm). After that, the two groups of subjects were divided into an allergic group and a control group according to the allergen sIgE test results (1 allergic, 2 nonallergic). The test results are shown in Table 18.19.

(a) Does the prick diagnostic kit have diagnostic value for birch pollen allergy and for Fraxinus pollen allergy? Draw ROC curves and perform a significance test.

(b) Determine an optimal cutoff for question

(a) (assuming no specific preference between sensitivity and specificity) and calculate the 95% CI for sensitivity and specificity.

(c) Is the diagnostic accuracy of the prick diagnostic kit the same for the two kinds of pollen? Make a comparison by using and not using the optimal cutoffs.