Comments on: Diagnostic Precision from Sensitivity, Specificity and Prevalence http://lingpipe-blog.com/2009/08/26/diagnostic-precision-from-sensitivity-specificity-and-prevalence/ Natural Language Processing and Text Analytics Wed, 08 Feb 2012 17:47:08 +0000 hourly 1 http://wordpress.com/ By: Owen M. http://lingpipe-blog.com/2009/08/26/diagnostic-precision-from-sensitivity-specificity-and-prevalence/#comment-7061 Wed, 09 Jun 2010 00:02:16 +0000 http://lingpipe-blog.com/?p=2036#comment-7061 Starting a site much like this one got me to get into some research and I found your post to be extremely helpful. My site is centered around the idea curing cancer by stopping the angiogenic process. I wish you good luck with your research in the future and you can be sure I’ll be following it.

]]> By: lingpipe http://lingpipe-blog.com/2009/08/26/diagnostic-precision-from-sensitivity-specificity-and-prevalence/#comment-5842 Tue, 17 Nov 2009 18:41:06 +0000 http://lingpipe-blog.com/?p=2036#comment-5842 Why am I not surprised by a new set of recommendations from the United States Preventive Services Task Force. Other groups are sticking with a recommendation of 40. There’s more info in:

In the calculations above, we were being fairly generous with diagnostic accuracy estimates.

These numbers need to be constantly updated due to changes in sensitivity and specificity of the test(s).

In a fuller model, the exact age at which it makes sense to be tested will also vary based on predictive features of the patients, such as genetic profiles. These would change the prevalence in the above calculations, and thus the received diagnostic precision for patients with a given set of predictors (e.g. age, genetic profile, health history).

]]> By: lingpipe http://lingpipe-blog.com/2009/08/26/diagnostic-precision-from-sensitivity-specificity-and-prevalence/#comment-5343 Wed, 26 Aug 2009 22:19:13 +0000 http://lingpipe-blog.com/?p=2036#comment-5343 Great points. Indeed, you often only get tests when there is some reason to believe you fall in a high-prevalence group. Much of the epidemiology literature’s concerned with multiple tests, which requires estimating correlation among the tests to derive sensible final estimates.

Mammograms are screening tests, at least in the U.S. if you’re following NCI’s advice. Even simple needle biopsies are not completely without infection risk and local anesthetic risk. Of course, surgical biopsies are more dangerous, but they also have higher sensitivity. The major risk seems to be false positives resulting in needless major surgery; I have no idea how big a risk that is for breast biopsies.

]]> By: Ken http://lingpipe-blog.com/2009/08/26/diagnostic-precision-from-sensitivity-specificity-and-prevalence/#comment-5342 Wed, 26 Aug 2009 21:59:54 +0000 http://lingpipe-blog.com/?p=2036#comment-5342 This is fine, provided the threshold for a positive is chosen (if possible) to give sensitivity and specificity that result in sensible outcomes. Missing breast cancer has serious consequences but a false positive simply results in a biopsy which can be easily done, so it is not a problem. This is something that people are researching in other areas, the consequences of each decision, but it requires decent data on what happens in each of the four possible outcomes.

One problem is that many diagnostic tests are designed to be used after some other symptom is found, not as screening tools. A headache without other explanation and with certain symptoms deserves a scan, and anything found can be a possible cause. No symptoms and anything found is probably unimportant, but now there is a dilemma, should they have a look or just wait and see what happens. Not a lot of data on this but neurosurgery can have severe consequences so nobody should do anything unless there is an obvious defect.

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