5.88 Screening for heart attacks Biochemical markers are used by emergency room physicians to aid in diagnosing patients who have suffered acute myocardial infarction

(AMI), or what’s commonly referred to as a heart attack.

One type of biochemical marker used is creatine kinase (CK). Based on a review of published studies on the effectiveness of these markers (by E. M. Balk et al., Annals of Emergency Medicine, vol. 37, pp. 478–494, 2001), CK had an estimated sensitivity of 37% and specificity of 87%. Consider a population having a prevalence rate of 25%.

a. Explain in context what is meant by the sensitivity equaling 37%.

b. Explain in context what is meant by the specificity equaling 87%.

c. Construct a tree diagram for this diagnostic test.

Label the branches with the appropriate probabilities.