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Dear Jeremy CEA carcinoembryonic antigen was suggested as a screening tool based on a diagnostic study comparing those with cancer with medical students (it looked good in that setting) however when tried in the community lots of false positives as expected and now it is only used to monitor known ca bowel. It was the classic case of lack of spectrum of disease and i think written up in Alvin feinsteins book clinical expidemiology. It was also referred to in the original mcmaster papers on clinical epidemiology rounds CMAJ (early 80s) diagnosis Bruce Bruce Arroll MBChB, PhD, FNZCPHM, FRNZCGP Professor and Elaine Gurr Chair in General Practice University of Auckland Private Bag 92019 Auckland New Zealand ph 64-9-9236978 fax 64-9-3737624 email [log in to unmask]<mailto:[log in to unmask]> Physical address School of Population Health room 378 building 730 Tamaki Campus Corner Morrins and Merton Rd Glen Innes Auckland From: Evidence based health (EBH) [mailto:[log in to unmask]] On Behalf Of Jeremy Howick Sent: Tuesday, 3 April 2012 11:18 p.m. To: [log in to unmask] Subject: Diagnosis Hi, There are well-known examples of therapies that were not evidence-based and were shown to be harmful (treating stroke with leeches applied to the anus, treating ventricular arrhythmias after myocardial infarction with antiarrhythmic drugs, etc.) I'm looking for parallel examples of diagnostic tests or strategies that have been introduced without sufficient evidence and subsequently were revealed to be useless or harmful when the tests were rigorously evaluated in unbiased tests. Jeremy