Question 1. The receiver operating characteristic (ROC) curve Purpose : This que

Question

Question 1. The receiver operating characteristic (ROC) curve

Purpose: This question attempts to help you understand what a ROC curve is and how is it used in the development of diagnostic tests. Please read the assigned reading posted along with this exercise on Blackboard. It is a section of a chapter from: Fletcher RH, Fletcher SW. Clinical Epidemiology: The Essentials, 4th edition. Philadelphia, PA: Lippincott Williams & Wilkins; 2005. You can also find information on ROC curves in the Week 10 assigned reading from the Bowers, House, Owens, and Bewick book as well as the Blumenschein and Goodin chapter in your textbook. The Dawson & Trapp book available through AccessPharmacy also has information about ROC curves. After you have read about ROC curves, please answer the following:

a)      T / F       A ROC curve can be used to help determine the optimum cut-off point for a diagnostic test. (Simply circle the correct answer).

Graph:

The areas under the curve (AUC) for the three receiver operating characteristic (ROC) curves were as follows:

AUC Ranson                           0.817

AUC Apache II      0.618

AUC Apache III     0.676

Which of the tests had the best ability to discriminate between patients with mild and severe acute pancreatitis? (Simply circle the correct answer).

a.      Ranson

b.      Apache II

c.      Apache III

Explanation / Answer

Answer to the question:

Concept:

ROC is a plot of the true positive rate against the false positive rate for the different possible cutpoints of a diagnostic test. The ROC therefore, is used to find the optimum point ( cutoff) where 1-Specificity is low and Sensitivity is High.

Answer is TRUE

a. The AUC Ranson has the highest ROC of .817 amongst all AUCs. Hence, a. Ranson is the answer

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