Recently there have been a number of advertisements claiming that drugs like Lipitor can cut your risk of stroke in half. Is this something to get excited about? It all depends on your risk of stroke.

If your risk of stroke is low, say 2%, then Lipitor will cut your risk of stroke to 1%. Is that reduction worth the extra expense and potential side effects associated with taking the medication? On the other hand, if your risk for stroke is 20%, then Lipitor may cut your risk down to 10%. That sort of reduction would convince many people at risk to take Lipitor. In both scenarios there is a 50% reduction in risk, but the need to take the drug is different. It all depends on level of original risk.

The same logic applies to screening and testing for health problems. With the recent death of Senator Ted Kennedy from a brain tumor, we may witness a phenomenon called the availability heuristic. Availability heuristic refers to people overestimate the future probability of an event occurring because of recent dramatic, publicized events. Thus some people may overestimate their chances of getting a lethal brain tumor because of Kennedy’s highly publicized death. If you are one of those people, there are plenty of places willing to give you a costly brain MRI even though you are currently asymptomatic (healthy) (www.brainscans.com is one such place).  

Well, if you are rich, then what is there to worry about? Why not get the screening done? The answer is that some tests can be harmful and others can lead to false positive results that may result in unnecessary additional testing and therapies.

Take, for example, those full body scanning centers that have recently popped up around the USA. Otherwise healthy people go to these centers to get scanned for diseases for which they are at low risk. Well, if they are rich enough to light their cigars with 100 dollars bills, then why worry, right? Wrong.

Several of the scans utilize CT technology. CT scans typically irradiate at higher levels than traditional x-rays. For instance, a chest x-ray delivers a dose of approximately 0.06 mSv, while a chest CT scan can deliver anywhere from 2.0 to 8.0 mSv, depending on the type of CT scan. That's a major increase in levels of irradiation for healthy individuals.
(Source: http://www.hps.org/publicinformation/ate/q2372.html).

Such tests are usually called for if a patient is symptomatic, has a history of disease, or has other risk factors. If none of these apply and a patient is in good health, the test may do more harm than good. Most physicians are aware of these issues, so check with your doc when considering screening tests.
 


Comments

Joseph Smidt

Thu, 27 Aug 2009 4:00:40 pm

"Availability heuristic refers to people overestimate the future probability of an event occurring because of recent dramatic, publicized events. "

Man, this seems to happen all the time. For example, one person will get attacked by a shark and people immediatly decide they are too scared to go to the beach.

The reality is, this happens to like one in a million people a year and now everybody is scared.

On the other hand, every day somebody will die driving somewhere like the beach, but that doesn't scare anyone away. (Nor should it by the way. Being killed on the road is also highly improbable, but much more likely than a shark attack.)

Interesting how psychology works.

 

Stan

Thu, 27 Aug 2009 5:56:16 pm

I wonder if it boils down to a matter of control. People want to be in control of their health and want everything checked and fixed. People are afraid to fly in airplanes, which they know are much safer, because they are not in control.

 

Jared*

Thu, 27 Aug 2009 7:06:55 pm

You neglected to mention that the problem of false positives becomes worse the rarer the disease is.

 

Dave C.

Fri, 28 Aug 2009 1:27:17 pm

It is only "neglect' if it is important to mention.

 

Jared*

Fri, 28 Aug 2009 3:43:34 pm

Dave,

I apologize if my comment came across as critical. I just thought it was a natural way to tie both of your posts together. It was intended to be helpful.

 

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