Genomics in Primary Care Setting

Genetic testing is an ever expanding field gaining more and more complexity, public attention, and a more active role in a primary care setting. For some genetic counselors this can be quite intimidating to know that health care providers with little to no training in genetics are being asked to order and possibly interpret genetic testing. This desire comes as much from the healthcare field as much from the media advertising the availability of testing and what it can predict for patients.

At this time, over 2000 different diseases with genetic testing available. It has often been simplified that a mutation (misspelling) one one particular gene will cause one particular genetic syndrome. In reality, we know that this just isn’t the case and on particular gene can cause several different syndromes (FGFR3 for example when mutated can cause achondroplasia, thanatophoric dysplasia, hypochondroplasia, Muenke syndrome). At the same time some syndromes are caused by many different genes (Noonan syndrome can be caused by mutations in at least 10 different genes). We also can’t forget about the multifactorial conditions such as congenital heart defects, spina bifida, autism etc which are likely to have genetic predisposing factors, but can also be influenced by environmental/prenatal exposures such as folic acid deficiency, maternal diabetes etc. Newer testing strategies are able to identify more and more of these genes which are possibly influencing a patient’s symptoms, but this same testing is increasing the uncertainty and complexity of the results received.

Exome sequencing (the spelling out of the functional portions of nearly 20,000 genes) has been available for more than a year now. In our pediatric clinic we are typically offering it to those patients with multiple abnormalities (such as a heart defect, cleft lip, and developmental delays) that has not had cause identified with previous “basic” genetic testing. It is not uncommon for a result to return with 30, 40, even 80+ variants in genes of unclear clinical significance. This is not including the likely hundreds of variants that are deemed by the lab as benign or unlikely to be related to genetic disorders/symptoms. This is a lot of complex data to sort through with limited information available and this type of testing is nothing compared to the uncertainty that is likely coming with more and more comprehensive/complex testing options.  Genetic counselors will be critical for providing informed consent for this type of testing and help families and health care providers in the decision making process regarding these new complex tests. To help with this process the CDC has developed a three tier evidence-based classification schema for genomic applications in public health and clinical settings.

Tier 1 includes tools that are recommended for clinical use by evidence-based panels based on a systematic review of analytic validity, clinical validity and utility for specific clinical scenarios”.  This tier includes newborn screening, hereditary breast and ovarian cancer, and Lynch syndrome.

Tier 2 includes tools that “have demonstrated analytic and clinical validity; hold promise for clinical utility but evidence-based panels have not examined their use or found insufficient evidence for their use.”  This tier includes family history screening for depression, several genes known for t tumor risk markers, pharmacogenetics, etc.

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Tier 3 includes tools that “have not demonstrated adequate analytic validity, clinical validity, or clinical utility. This also includes applications for which evidence-based panels have recommended against their use based on the synthesis of the balance of benefits and harms.”  These include routine BRCA mutation testing without a clear family history indicating is utility, exome sequencing, and genetic risk for common diseases.

The propose is to help health care professionals understand and therefore help their patients understand which tests are likely to be most relevant and informative choices.  There is also discussion regarding a technique known as “cascade screening”.  According to the CDC, cascade screening is “an active process to find relatives of persons affected with certain genetic conditions, for which interventions exist that that can save lives”.  This is based on the idea that even though each individual genetic disease may be rare, as a collective whole they affect millions of people.  By using an approach which targets those indivdiuasl that may be at higher risk (family members of an already diagnosed individual) we can target those patients which may benefit most from these newer and sometimes more experimental techiques using health care dollars responsibly.  This is something quite familiar to genetic counselors as we are often discussing the risks for other family members beyond a specific patient in front of us with a particular genetic disorder.  Genetic counselors have the skills to assist with this transition for genetics as a specialty with geneticists as the gate keepers to testing in a primary care setting.  Though this is a long way off, I think it will be important to consider this as we look to the future.  How will we fill the gap between the few thousand genetic counselors in the country and the hundreds of thousands of primary care physicians?

http://blogs.cdc.gov/genomics/2012/11/29/genetic-counseling/