Chronic Wasting Disease
Spreading In Wisconsin

From Patricia Doyle, PhD

According to the assessment of the rapid diagnostic tests, there would not be "false positives" as mentioned in the previous CWD (Wisconsin) update.
The statement below indicates more chance for false negatives. In other words, a deer who has contracted CWD might not test positive.
This information then clarifies the article posted yesterday regarding the increase in CWD cases in Wisconsin and indicates that many more CWD ARE BEING identified with the tests. In other words, CWD is on the rise dramatically.
Patricia Doyle
A ProMED-mail post
ProMED-mail, a program of the
International Society for Infectious Diseases
Date: 18 Mar 2004
From: Geoffrey Fosgate
There seems to be a minor error concerning the interpretation of the diagnostic properties of the IDEXX HerdChek for CWD. A sensitivity of 98.8 percent and specificity of 100 percent would suggest no false-positive results, but a small proportion of false-negative results.
Perfect specificity would be a little unusual given the nature of the detection platform. I tend to be cautious when interpreting sensitivity and specificity estimates independent of information concerning the sample size, sample selection, and gold standard determination.
Geoffrey T. Fosgate DVM, PhD, DACVPM
Assistant Professor, Epidemiology
Department of Veterinary Anatomy and Public Health
College of Veterinary Medicine
Texas A&M University
College Station, TX 77843-4458
[ProMED-mail appreciates Dr. Fosgate's correction and agrees with his
caution regarding the manufacturer's claim of perfect specificity. -
Patricia A. Doyle, PhD
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Zhan le Devlesa tai sastimasa
Go with God and in Good Health



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