Diminishing returns on the road to diagnostic certainty
Article Abstract:
While amassing the most information possible concerning a patient may seem the best strategy for arriving at a diagnosis, this may not be the case. In fact, trying to reach an increasingly more certain diagnosis may lead to the accumulation of test results that do not add any useful information. A discussion is presented of an approach for determining the information content (hence, usefulness) of diagnostic tests. The amount of information in a message is related to the probability of that message being sent (the example is used of a report of snow in June versus the same report in February; the first message carries more information because it is less likely). It is possible to calculate the information value (hence, usefulness) of a test result. This can be done by comparing the pretest probability of a disease with the post-test probability of the disease: has the test increased the chance that the disease is present? Sample calculations are carried out. As the certainty regarding the diagnosis increases, the useful information provided by a test decreases and the cost increases. This is particularly apparent if the cost per bit (a unit of measure) of useful information, rather than the cost per test, is calculated: for a patient diagnosed after examination and electrocardiography as having a 50-50 chance of having had a heart attack, performing a certain blood test (creatinine kinase) will add 0.085 bits of information and bring the certainty of diagnosis to 99.8 percent. Performing another blood test (lactate dehydrogenase) will yield only 0.003 bits of additional information for $2,000 per bit; clearly this test is of little use. The quality of diagnostic tests is not at issue; rather, the number ordered and the sequence in which they are performed determine their usefulness. While diagnosis cannot be reduced to an algorithm, physicians should keep in mind the law of diminishing returns when presented with diagnostic questions. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: JAMA, The Journal of the American Medical Association
Subject: Health
ISSN: 0098-7484
Year: 1991
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Adenosine, antioxidant enzymes and cytoprotection
Article Abstract:
Recent studies have shown the effectiveness of adenosine against ischaemia and reperfusion. Adenosine is created by the action of various membrane-associated enzymes on ATP, ADP and AMP during normal metabolic activity. The nucleoside mediates the physiological actions of adenosine by activating adenosine receptors. The cytoprotective action of the adenosine receptor subtype A(sub 3) is discussed.
Publication Name: Trends in Pharmacological Sciences
Subject: Pharmaceuticals and cosmetics industries
ISSN: 0165-6147
Year: 1995
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Terminating termites
Article Abstract:
Techniques for tackling termites are discussed. Dow AgroSciences' Sentricon system uses monitored stations placed in the ground to detect and eliminate subterranean termites.
Publication Name: Southern Living
Subject: Home and garden
ISSN: 0038-4305
Year: 2000
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