Think (Again) Before You Spit: Readers Weigh In

We thank our readers for their thoughtful comments on our recent post, which discussed the validity and utility of personal genomic tests for improving health. Clearly, this topic engenders a range of reactions as reflected in a recent scientific discussion. Several people I know have sought testing for various reasons, including curiosity, genealogic research, or just for fun. I’ve even been tempted a few times to be tested myself. However, when I looked at the scientific evidence for the accuracy, validity and utility of the information I would receive from such testing for the purpose of improving health and preventing future disease, I decided not to do it–at least not yet. I may change my mind in the future as the science matures. And of course, each person is free to make their own informed decision.

As public health professionals, our goal is to provide unbiased information so that consumers can make the best decisions for themselves, with a full understanding of the potential benefits and limitations of these tests. We would like to follow up on a few points raised by the readers.

1. Should genetic information be included in public health databases?

There are many issues to consider before public health agencies can use this information for epidemic control or management. For example, recent debate about the use of residual newborn blood spots points to legal, social and ethical issues that have not been resolved. Although public health agencies are beginning to integrate genetic information in outbreak investigations and surveys, we do not know enough right now to use this information to mitigate adverse vaccine effects or target intervention strategies.

2.  What do we really know about the validity and utility of personal genomic tests?

We may assume that genomic information can only improve our health because it gives us additional reasons to be healthy, such as exercising more or stopping smoking. But what if it raises unnecessary worries, gives us false reassurance, or leads to unnecessary medical procedures, which have their own risks? Consider the nationally known television personality, who–after taking a genetic test was told that his risk for prostate cancer was 30% lower than the average risk–said “thanks to this test, I don’t have to have rectal exams.” What if the results are not reliable? Studies by the US Government Accountability Office and others discovered that saliva samples from the same people sent to different companies came back with completely opposite interpretations of the risks for serious diseases like prostate cancer and diabetes. They can’t all be correct. And wrong information is never a good basis for decision-making.

Even reliable information can lead to both benefits and harms. In this respect, genetic information is no different from other health-related information. The scientific literature over many decades has documented harms resulting from all kinds of screening tests, including inappropriate medical treatment or unnecessary surgery.  A recent study of a selected sample of more than 2000 subjects who completed 3 months follow-up after undergoing personal genomic testing found that such testing did not result in any measurable changes in psychological health, diet or exercise, or use of screening tests. One may be reassured that no major harms were documented but at the same time be concerned that no health benefits were shown as a result of testing. Clearly, in order for personal genomic tests to make any difference in improving health, we need to conduct additional research on the benefits and harms of genetic tests in the same way we collect research data about other types of health information.

3. Is family history a better tool than personal genomic tests for improving health?

Although family health history has been used in clinical practice for generations, as an aid to diagnose and manage hundreds of genetic disorders, it has its limitations, including lack of access to this information for many people.  As a screening or predictive tool, an NIH state-of-science conference in 2009 concluded there is insufficient evidence for the utility of family history in improving health. CDC just finished the first randomized clinical trial of its kind to evaluate the impact of a family history-based intervention on health and screening behaviors. Results of this trial include potentially encouraging findings in terms of improved diet and physical activity.  Last year, we wrote a paper comparing the evidence base for family history and personal genomic tests.  We concluded that both deserve to be studied–and not necessarily only in long-term, randomized clinical trials.  We even suggested evaluating the utility of personal genomic information together with a family health history.

4. How can we ensure that validated genomic applications become available to everyone?

Public health agencies work diligently to ensure that valid and useful tests become widely accessible to everyone, regardless of educational or other factors. Plenty of evidence suggests that there are major disparities in access and use of many tests, including genetic tests, which are known to improve health outcomes. On the other hand, for tests that have not been validated, such as personal genomic tests, consumers should have access to the best available scientific information when deciding whether taking these tests is worth their spit.