Wednesday, April 29, 2009

Why Family History Matters

I am often asked by my patients why I take such an extensive family history. They also often ask, why their other doctors have never done so before.

The short reason, you very rarely find anything you that aren't looking for. True there are incedentalomas of CT scans that end up saving someone's life. But those are the rare cases.......True, there are some doctors who are so busy that they order a zillion tests in a shotgun approach because they are too busy to think through a case, let alone take a 10 minute family history.

But I am not one of those doctors.

Just yesterday patient comes in with increased thirst and increased urination......this case was classical diabetes. But I also decided to take a family history.......

It turns out he has early onset cancers in the family. A stomach and an ovarian. 2 very rare cancers which most doctors would not have caught. Why? No one teaches you about Lynch Syndrome in Internal Medicine residency. More importantly, they wouldn't have had the time to work out the pedigree if they were double booked seeing 20 patients a day.

So in addition to the diabetes work up this patient is getting, he is also getting a cancer genetics evaluation by myself. Something I am very good at. Something I teach my residents about everyday. Why? Because I know they won't get this stuff anywhere else.

So when I see a blog post from a DTC company that says Family History isn't enough, I laugh. Compared to the testing that this company is offering, Family History IS everything and more than a 2500 USD test could offer.

"Navigenics assesses genetic risk for many common health conditions, including Alzheimer’s disease, breast cancer, type 2 diabetes, prostate cancer and heart attack."

As you can see from the links...genetic testing here just isn't that useful.....Which is why it is a shady practice to misrepresent it as USEFUL.

Family History as well as a good physical exam with our current risk algorithms does a far better job than a non-clinically validated SNP scan that costs 2500 USD does......

The clinical ramifications of this man's family history make SNP scan testing foolish, but Tumor sample and Germline testing the STANDARD OF CARE. No SNP scan would lead me to do either of those tests.........But the right family history? You bet your bippee.....

In a world where Comparative Effectiveness Research is taking place, we will soon see the SNP scan placed in a lower level of test and probably not be in the clinicians armamentarium.......unless of course the results (good, bad or useless) can get patients to do something that a good relationship with a doctor has not been able to do......i.e. quit smoking, lose weight, etc.

The Sherpa Says: I am sick and tired of journalists hired as "Health Writers" hyping a false product to improve sales.....This is a crappy thing to do to vulnerable people reading your swill....


Anonymous said...

Family history IS critical in honing in on the possibility of a hereditary cancer syndrome like Lynch syndrome. However, HNPCC is responsible for only 2-3% of all colorectal cancer cases. What about the other 97%, in particular the 70% of cases that are not even familial? Testing for common SNPs that have a small to moderate effect on disease risk can help identify those who are at increased risk in the absence of family history. Shouldn’t we be using every tool in our arsenal to aid in early detection and prevention of disease?

Steve Murphy MD said...

Yoon and colleagues demonstrated how even fairly simple family history information could be used to clarify the risk of a number of common, complex disorders. Based on published data.

They suggested that a healthy 23 year old man could have the following lifetime risks of:
• 60 percent for cardiovascular disease (based on one male first degree relative (1DR) diagnosed after age 60)

• 50 percent for colorectal cancer (based on two 1DRs diagnosed before age 50); and

• 30 percent for type 2 diabetes (based on one 1DR diagnosed after age 60

Can those GWAS research tests do that?

No. Stop painting Lynch as so rare. It is much more common than we have detected. HNPCC is way more common than Huntingtons. etc.

The argument you pose demonstrates your lack of understanding re: utility of family history

There is way more data on this than on the SNPs....


bmw said...

Music to my ears, thanks gene sherpa!

Sarah H. said...

Hi Dr. Murphy--I'm a clinical genetic counselor and a very recent reader of your blog. Just wanted to say thanks! DTC testing is something we didn't learn too much about in or course work, but patients do ask about it. I am happy to have found your blog. Thanks again