Tag Archives: pharmacogenetic testing

Can You Trust Genetic Tests for Meds?

Last week, the FDA approved yet another direct-to-consumer pharmacogenetic test. This one will help determine how your body metabolizes medications based on genetic variants. Do you need it?

The short answer is no.

The test, from 23andMe, analyzes a saliva sample and based on 33 genetic variants can predict how that person will metabolize medications. That’s it. It can’t predict how a person will respond to a particular drug, a finding that would be quite useful.

So why is knowing how you metabolize a drug important at all? A drug metabolization rate can influence a drug’s efficacy and side effects. Yet, 23andMe admits that the test only predicts whether a person is a slow or fast metabolizer of medications in general. It doesn’t provide any information on, say, if a person is a slow metabolizer, how that should influence prescribing of a drug.

With this in mind, what is the usefulness of this test for the consumer? It appears to be quite limited. Even the FDA admitted as much. “This test… does not determine whether a medication is appropriate for a patient, does not provide medical advice and does not diagnose any health conditions,” Tim Stenzel, director of the FDA’s Office of In Vitro Diagnostics and Radiological Health, said in a statementHe added that consumers should not use results from the test to make treatment decisions – such as stopping a medication – on their own, but undoubtedly many of them will.

The Test Could Lead to… Another Test

The idea is that patients would take the test results to their doctors for further discussion. Yet even then the utility of the test appears limited. “Healthcare providers should not use the test to make any treatment decisions,” the FDA said. “Results from this test should be confirmed with independent pharmacogenetic testing before making any medical decisions.”

In other words, after getting the 23andMe test and showing them to your doctor, you will need even more testing before any decisions are made on medication changes.

There’s been a recent proliferation of pharmacogenomic testing that has become available. Many of them tout their ability to predict a person’s response to certain medications, allowing doctors to select the most appropriate drug for a patient. Yet, despite heavy marketing, the tests may not be backed up by appropriate scientific or clinical evidence.

Perhaps that’s why a day after the the approval of the 23andMe test, the FDA issued a warning that many such genetic test claims have not been substantiated by the agency. The FDA also noted that “selecting or changing drug treatment based on the results from insufficiently substantiated genetic tests… could lead to potentially serious health consequences for patients.”

I look forward to the day when a genetic test can actually help determine the best medication for a patient for a given condition. But we’re not quite there yet. Until then, understand that many of these tests have limited benefit to patients and are often nothing more than a waste of money.

Can a Test Take the Guesswork Out of Prescribing Meds?

Here’s the promise: A simple test, taken in a doctor’s office or even a drug store, will predict which medicine is the right one for you. No guessing, no false starts, no terrible side effects.

Here’s the reality: Not yet.

This is the growing area of pharmacogenomic testing, which for medications means predicting which drugs will work well inside of your body based on certain genes you possess. But at the moment, the testing has not demonstrated it is as good as its developers make it out to be.

The testing is of particular interest for those taking psychiatric drugs, where it can often take several tries before a medication that works for a given condition is found. For example, only 40 to 60% of those with depression find success with the first antidepressant prescribed.

Pharmacogenomic tests are becoming more widely available. As an example, back in May, grocery chain Albertsons, which also operates drug stores, began offering pharmacogenomic testing for psychiatric medications for customers at 28 of their pharmacy locations through a partnership with Genomind.

‘The Marketing Is Way Out Ahead of the Data’

A recent article in JAMA discussed psychiatric pharmacogenomic testing, interviewing doctors and other health care professionals. The bottom line: Pharmacogenomic testing for psychiatric meds may work, but the evidence so far is limited.

James Potash, MD, with the department of psychiatry and behavioral science at Johns Hopkins, said that the evidence for the tests has come mostly from small trials conducted by the manufacturers. Perhaps that’s why he told JAMA that for some tests, “the marketing is way out ahead of the data.”

A piece published in August in JAMA Psychiatry examined the trials behind 10 pharmacogenomic tests that are marketed to help determine the ideal medication choice for treating major depression. The authors found issues with the way all 10 trials were conducted.

A consensus is growing, according to the JAMA article, that pharmacogenomic testing may be more useful for predicting side effects than for a person’s response to a particular drug. So far, there is no test than can tell you, for example, what the “right” antidepressant is for a given patient, according to Potash.

An American Psychiatric Association task force this year also came to the conclusion that there is not enough evidence to support widespread use of pharmacogenomic testing, though “it may be informative, particularly in predicting side effects.”

There are other concerns. Just because an individual has a gene linked to a particular side effect doesn’t guarantee they will definitely experience that side effect. Along the same lines, lacking that gene doesn’t mean you won’t experience it or other effects. Many genes influence side effects you might experience, as do other health conditions and medications you are taking. In other words, pharmacogenomic tests can complement, not replace, existing clinical tools.

And then there is the cost — pharmacogenomic tests can easily cost hundreds of dollars.

To me, pharmacogenomic testing for drug side effects and efficacy holds great promise, but we are not there yet. If you decide to get a test, understand its limitations.

This Test Could Save Your Life

Wouldn’t it be great if there were some sort of test you could take to predict which medications are most likely to work best for you personally, and which ones could hurt you with an adverse reaction? Good news: There is such a test, and although you probably haven’t heard of it, it’s not some out-of-reach possibility for future use – it’s starting to pop up at medical centers around the country.

Just as your genes determine traits like eye color and whether you have dimples or freckles, they also influence the way each individual reacts to medications. That’s one big reason that a particular drug might work well and cause no problems for one person, might not have any helpful effect in another person, and pose a life-threatening risk to someone else.

The drug-response test known as PGx (pharmacogenetic) testing uses a small sample of a patient’s blood or saliva to look for genetic differences in their DNA that could show whether a drug is likely to be effective, whether it is likely to cause side effects, and what the best dose is for that person.

What PGx Tests Are – And Are Not

There are different PGx tests, depending on the medicine. Here is a list of PGx tests from the Mayo Clinic, along with the medicines for which they test. p Not every drug has a PGx test, and no OTC drugs have PGx tests.

There are limits — a “normal” PGx test result doesn’t guarantee you aren’t at risk for an adverse event or that the drug is ineffective for you. Current tests only capture the variants we know about now. Future tests will certainly improve and add more genes.

Though PGx testing is already available in some places, it isn’t yet widespread, and insurance coverage is still limited. “Drugs that are known to work differently based on a person’s genetics are likely to be covered – for example, clopidogrel, warfarin, fluoxetine, simvastatin and abacavir,” explains Mohamed A. Jalloh, PharmD, assistant professor at Touro University California College of Pharmacy and spokesman for the American Pharmacists Association.

Does Medicare Cover It?

Medicare does pay for the test, but commercial insurers are taking it slower. “PGx testing is an emerging field, so many insurance plans have not started covering it,” notes Dr. Jalloh. In a recent analysis, only 3 of 65 health insurance policies reviewed were found to cover PGx testing.

And plans that do cover it are likely to do so only when it’s deemed medically necessary, rather than for any patient who is interested in being tested. (As an example, this is Cigna’s policy. [pdf]) That may change as awareness about the test continues to grow, especially since a recent study found that 1 in 4 patients has a drug-gene association that poses a serious risk.

Because PGx tests your DNA, some might worry about privacy issues. Be assured that federal law 31 “prohibits any use of genetic information by health insurers and employers, though other groups may still use this information (eg, life insurers and the military).”

Here are 5 more things you should know about PGx testing:

1. It is likely that the results of taking the test one time will be useful for drugs in the future. Many commonly prescribed drugs interact with only a small number of genes. For that reason, taking the test once might cover you for drugs you need in the future. Therefore, make sure you or your healthcare providers are sharing the results with all of your doctors and your pharmacist.

2. The test itself takes 2 minutes, but it can take anywhere from 5 to 14 days for a lab to process it and provide results. “Certain medications may be started in the meantime to avoid the risks of treatment delays,” says Dr Jalloh.

3. The testing covers over 330 commercial drugs, including all FDA “black-box” drugs – about 155 or so – for which the test is required or highly recommended, according to Sternfeld. These medications have been linked with serious or life-threatening side effects. (https://www.fda.gov/downloads/forconsumers/consumerupdates/ucm107976.pdf)

4. “There is also a huge savings in patient healthcare costs as it eliminates trial-and-error prescribing plus the costs of hospitalizations for adverse events,” Sternfeld says.

5. Certain medical centers are more likely to offer testing than others. University hospitals affiliated with PhD programs that focus on pharmacogenomics are likely to offer the testing. “Also, some pharmacy schools are leading the way in research and training – for example, the University of Colorado Skaggs School of Pharmacy and the College of Nursing has a pharmacogenetic training program, therefore hospitals or clinics affiliated with the school may be possible choices for testing,” states Dr. Jalloh. (h)

What to Ask Your Doctor

In general, patients should ask their pharmacist if any of their current medications may work differently based on one’s genetic makeup, Dr. Jalloh suggests. “Patients should ask for this evaluation anytime their pharmacist does a comprehensive medication review or medication check-up.”