This paper reports a new 'screening' test for Alzheimers disease. More below on use of the word 'screening' in this context.
Good points:
a. validated against people with a firm clinical diagnosis, made by experts, of Alzheimers disease (i.e. concurrent validation, against a 'gold standard');
b. ROC comparison against the current screening test - the Mini Mental State Exam. The correct way to compare two screening tests is the ROC curve.
c. age specific norms published - i.e. what 'normal' people score on this test.
Although the test is described as a screening test I would classify it as a clinical algorithm, given its intended use in hosptial and other clinics. I certainly hope it won't be used in the general population without more validation, though unfortunately the authors have put the test on a website for anyone to try.
There is some debate about whether tests like this are 'screening' or not. Both population screening and clinical testing start with a prior probability of disease which changes to a higher (or lower)probability after the result is known. In a clinical setting the prior probability of disease is higher: the patient has come to the clinic because something is wrong.
On the other hand the ethics are certainly different. In population screening we invite ordinary people who are happily going about their business and tell them they may have some serious disease. With clinical tests, the doctor is sifting through the possibilities for someone who has asked what is wrong with them.
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