Statistical test for sensitivity and specificity

Hi everyone, I'll make this as quick and easy as possible :)

I've carried out a project where I compare the efficiency of two tests used for the screening of G6PD deficiency. My premise for comparison is to compare the specificty and sensitivity of the tests. I do this by determining the number of true positives, true negatives, false positives and false negatives. To compare the accuracy of each of the screening tests in its ability to reflect the true G-6-PD status, the following were calculated

Specificity: d/ (b+d) × 100
Sensitivity: a/ (a+c) × 100
a = true positives
b = false positives
c = false negatives
d = true negatives

and also calculate the positive predicted value = a/a+b

Now seeing as my data is qualitative I was wondering what statistical would be most suitable? I presume it is non-parametric methods as my data is distribution free?

Also would the best way to display the data be by the use of bar charts?

Thank you :)