David A. Nardone, MD
To the Editor: The serologic marker for pancreatic cancer, CA 19-9, is more useful than presented in the study by Pleskow and colleagues (1). Its value is not shown by comparing CA 19-9 to carcinoembryonic antigen at a cutoff of 70 U/mL (P < 0.0001) but by doing calculations for true-positive rates (sensitivity), false-positive rates (1 — specificity), and for likelihood ratio-positive at different cutoff points: for 10 000 U/ mL: true-positive rate, 0.19; false-positive rate, 0.01; likelihood ratio-positive, 19; for 1000 U/mL: true-positive rate, 0.39; false-positive rate, 0.01; likelihood ratio-positive, 39; for 100 U/mL: true-positive rate, 0.63; false-positive rate, 0.10; likelihood ratio-positive, 6.3; and for 70 U/mL: true-positive rate, 0.70; false-positive rate,
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Nardone DA. The Serologic Marker CA 19-9 and Pancreatic Cancer. Ann Intern Med. 1989;111:184-185. doi: 10.7326/0003-4819-111-2-184
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Published: Ann Intern Med. 1989;111(2):184-185.
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Print ISSN: 0003-4819 | Online ISSN: 1539-3704
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