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Genetic Test or Family History? Which Matters More?

Posted Nov 05 2008 12:05pm

I would say that when used in combination a 3 generation family history and appropriate genetic testing are probably the best tools we have to identify risk for and diagnose genetically linked disease.

So what matters more to patients? What risk means more? The results of a genetic test OR their family history. Hsien Lei touches on this briefly at Eye on DNA, but the interpretation she provides is not exactly what the article said or studied.....What article? Well the one I am about to tell you about...

Published in the Archives of Pediatrics and Adolescent Medicine this week an article entitled:


The article sought to study:
To evaluate the effect of the genetic risk information source (family history vs genetic test results) on parents’ concern about their own and their children’s genetic disease risk.

In lay terms, which mattered more and carried more weight when "assessing" risk by a parent....family history OR genetic testing.....
Hsien interprets thisFamily History of Disease Scares Parents More Than Genetic Test Results.... I wouldn't say scares......I would say concerns.....or means more to them.....
Fear was not studied in this analysis......Concern was....

The Method:

Parents first received a vignette about their hypothetical genetic risk, randomized as either a family history assessment or genetic test results. Next, parents received a vignette about their youngest child’s hypothetical genetic risk, similarly randomized.


The Vignettes:

Imagine that you have family members with a disease that causes severe symptoms in adults. Having this “family history” means that (you/your youngest child) has a 30% chance of developing this disease. A 30% chance means that 3 out of 10 people will develop the disease.
“How concerned are you that (you/your child) might develop this disease?”


AND


Imagine that (you/your youngest child)gets a genetic test result that says he/she has a 30% chance of developing a disease with severe symptoms in adults. A 30% chance means that 3 out of 10 people will develop the disease. “How concerned are you that (you/your child) might develop this disease?”


So this clearly is a high risk gene 30% likelihood is about what the risk is for Ovarian Cancer carrying a BRCA gene mutation. "Roughly" for my CGC readers who like ranges......

The Results:

Parents were more likely (twice as likely) to be concerned about their own disease risk when
the risk estimate came from a family history assessment vs a genetic test result (odds ratio, 1.96; 95% confidence interval, 1.44-2.68).

But here's where it gets interesting.......Patients perceive the risk of their child's as the same as their own.....clearly not a mendelian concept or even a genetic concept......Even more interesting was the fact that despite this being the case 73% of the time, the other 27% actually were concerned that their child's risk was HIGHER than their risk......
Ah.....you have to love denial!!!!!

Conclusion:

Positive family history of disease generated greater concern about parents’ own risk of inherited
disease than did genetic test results.

The Sherpa's Conclusion? People don't know what the hell they are doing when analyzing genetic risk. Nor do they know what the hell they are doing analyzing multifactorial disease risk in pedigrees....


So I ask you....."Should we expect them to?" Isn't this the exact reason why we have geneticists and genetic counselors? Our job is to interpret family histories and genetic test results....in the doctors' case they interpret full medical history, perform physical examination and review of systems and evaluate other lab values oh, and medication history too.......

Why should we expect patients to know or understand these concepts? Oh, I know why.....because we are trying to thrust onto themselves the diagnostic and interpretive responsibilities in some crazy screwed up way to save costs for the American Healthcare system.....By doing non-clinically valid DTC testing which will be pushed down our throats by Time magazine and the PR firms of the silicon valley DTC firms.....


Or at least that's what some one in this field told me......Personally, if you want to save healthcare costs....fire the coders, HR departments, compliance people, essentially fire everyone who doesn't lay their hands on a patient or handle their lab specimens.........That's where the fat is.....it is NOT in direct care.....


The Sherpa Says: Pedigree analysis, Bayesian Interpretation, Molecular Biology and Genetics are not taught in high school...why In the hell should we think everyone will be able to use DTC testing, which doesn't even throw family history into the mix......Silly....real silly......Stick with your Sherpa.....don't try to climb mountains on your own.....



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