Test results

Staphylococcus aureus

Other staphylococci

Total


Positive

a

b

a + b

Negative

c

d

c + d

Total

a + c

b + d

(a + b) + (c + d) = n

 Where,
 a = True positives
 b = False positives
 c = False negatives
 d = True negatives
 Diagnostic sensitivity = d/(b + d)
 Diagnostic specificity = a/(a + c)
 Positive predictive value (PPV) = a/(a + b)
 Negative predictive value (NPV) = d/(d + c)
 n = 60