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Hi Matt and all, I prefer to use the Universtiy of British Columbia Department of Epidemiology website calculator. You can find it at: http://www.healthcare.ubc.ca/calc/bayes.html It is a Bayesian calculator and if you have the 2x2 table, you'll get confidence intervals. Best wishes, Dan >>> Matt Williams <[log in to unmask]> 3/11/2008 12:27 AM >>> As a follow-up to this, does anyone know how to calculate confidence intervals on Sens & Spec? I'm assuming that when you replace one test with another, you won't get a perfect match in terms of performance parameters, so I'd be interested in knowing how you know when it's 'good enough' Thanks, Matt brnbaum wrote: > Teresa Benson posted: >> If you are using correlation coefficients to decide whether one >> clinical >> test can be substituted for another, particularly with non-dichotomous >> values (e.g., blood glucose), is there a certain minimum value you >> look >> for? (Assuming, of course, the new test is cheaper or easier.) Or do >> you always just look at things like sensitivity/specificity and >> predictive value, and disregard the correlation coefficients? The old >> User's Guide to the Medical Literature recommends a correlation >> coefficient of at least .8, but I'd like to know what others think >> about >> this. >> > > I'd recommend sensitivity, specificity, positive & negative predictive values, LR+, LR-, and McNemar's chi-square test as being more meaningful than correlation coefficients for this purpose. For non-dichotomous tests, it also would be appropriate to examine goodness of fit throughout the entire reported value range (new test might perform well in certain zones but not as well as the other test in other zones). Probably wise to check the literature on diagnostic test assessment so as to have a reference supporting the approach you select. > > David. > > -- > David Birnbaum, PhD, MPH > Adjunct Professor > School of Nursing > University of British Columbia > Principal, Applied Epidemiology > British Columbia, Canada -- http://acl.icnet.uk/~mw http://adhominem.blogsome.com/ +44 (0)7834 899570 **************************************************************************** Dan Mayer, MD Professor of Emergency Medicine Albany Medical College 47 New Scotland Ave. Albany, NY, 12208 Ph; 518-262-6180 FAX; 518-262-5029 E-mail; [log in to unmask] **************************************************************************** ----------------------------------------- CONFIDENTIALITY NOTICE: This email and any attachments may contain confidential information that is protected by law and is for the sole use of the individuals or entities to which it is addressed. If you are not the intended recipient, please notify the sender by replying to this email and destroying all copies of the communication and attachments. Further use, disclosure, copying, distribution of, or reliance upon the contents of this email and attachments is strictly prohibited. To contact Albany Medical Center, or for a copy of our privacy practices, please visit us on the Internet at www.amc.edu.