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Novel Internet-based Tool for Correcting Apparent Sensitivity and Specificity of Diagnostic Tests to Adjust for Referral (Verification) Bias¹

¹ From the Cardiovascular Division, Department of Medicine (P.G.D.), and Nuclear Medicine Division, Department of Radiology (J.A.P.), Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Ave, Boston Mass 02215. Received April 30, 2001; revision requested November 7; revision received and accepted December 6. Address correspondence to: P.G.D. (e-mail: pdanias{at}caregroup.harvard.edu)

View larger version (16K): [in a new window]   Figure A1.  In this flowchart, the CAD status (d) of the population (N) is represented in the second row. The TP, TN, FP, and FN test results can be calculated as a function of the test sensitivity (Se) and specificity (Sp). (+ CAD) = patients with CAD, (- CAD) = patients without CAD.

View larger version (18K): [in a new window]   Figure A2. Flowchart shows that when the study population is subject to referral bias for conclusive determination of disease status—p+ and p- for a positive and negative test result, respectively—apparent test sensitivity and specificity are measured (see text).

View larger version (22K): [in a new window]   Figure A3. Flowchart for calculation of the operative characteristics of a test with varying sensitivity and specificity depending on the test performance. A proportion k of the patients with CAD and a proportion m of patients without CAD will achieve at least 85% of age-predicted maximum heart rate. The sensitivity and specificity of the test is given by Se1 and Sp1 when at least 85% of maximum heart rate is achieved and by Se2 and Sp2 when less than 85% of maximum heart rate is achieved. p1+ and p1- are the referral rates for positive (+) and negative (-) test results for patients who achieved at least 85% of maximum heart rate, and p2+ and p2- are referral rates for positive and negative test results for patients who achieved less than 85% of maximum heart rate.