By Roger Chriss, Columnist
Prescient Medicine recently announced LifeKit Predict, a gene screening test to determine who is at risk for opioid addiction. The company states that it “can identify with 88% specificity that someone may have a risk for opioid dependency” and “provides assurance -- with 97% sensitivity -- that an individual may not have increased genetic risk for opioid dependency.”
Those are strong claims. The idea that medical conditions and behavior can be predicted by gene variants is appealing. But any such test has to answer two questions:
Is it possible in principle? And does it work in practice?
Genes and Behavior
The pathway from gene variant to behavior is very complicated. Research on the genetics of opioid addiction has found “evidence for genetic susceptibility to substance use disorders” in twin studies, but non-genetic factors are known to play a significant role as well.
Moreover, the connection between gene test results and clinically useful information is complicated. Genetic testing often finds pathogenic variants with no clinical significance. A person can be a perfect match for a rare disorder in the most advanced genetic test available but have no symptoms, so at a clinical level that person does not have the disorder. Only in a handful of cases does a specific gene variant lead to a precise fate: Huntington's disease is the standard example in textbooks.
Addiction is generally thought of in terms of the biopsychosocial model of medicine, as Maia Szalavitz explains in her book, Unbroken Brain.
“There are three critical elements to it; the behavior has a psychological purpose; the specific learning pathways involved make it become nearly automatic and compulsive; and it doesn’t stop when it is no longer adaptive,” she wrote.
The National Institute on Drug Abuse reports that “genetic factors account for between 40 and 60 percent of a person’s vulnerability to addiction; this includes the effects of environmental factors on the function and expression of a person’s genes.”
Thus, genes may play a significant role, but many other factors are also at work. A genetic test to identify an increased risk for opioid addiction is plausible in principle. But non-genetic factors make it tricky in practice.
Real World Performance
Prescient Medicine has not yet validated its product with large-scale testing in the clinical setting. There have been no clinical studies of efficacy, nor real-world reports of success or failure rates with the LifeKit Predict tool. These findings are important to know for effective use.
In research published on LifeKit Predict, Prescient acknowledges that “the use of genetic algorithms to determine predictive risk scores is still a relativey [sic] new science. Prospective, longitudinal studies are needed to better definne [sic] the breadth of the test’s importance."
A prospective trial of chronic pain patients with LifeKit Predict to see who develops opioid use disorder would be optimal. But for a variety of reasons, including ethical considerations, this test may not be practicable. Instead, Prescient could test people on long-term opioid therapy who did not develop opioid use disorder and compare the results with people who did develop opioid use disorder. Findings here would shed light on the validity of the 16 gene alleles that Prescient is using.
For now, Prescient is reporting on sensitivity and specificity. These two terms have a precise meaning in statistics, but the following medical example captures the essentials:
A molar (butterfly) rash is very sensitive for lupus but not very specific. It is rarely seen in any disorder other than lupus, so if a person has it, lupus should be suspected. But it is only seen in about half of people with lupus, so not having a butterfly rash doesn't mean you can rule out lupus.
But the sensitivity and specificity of LifeKit Predict in the ranges given by Prescient represent a significant risk for false positives and false negatives, potentially limiting the real-world value of the test.
GenomeWeb reported that Yale University professor Joel Gelertner, an expert in genetics and addiction, was skeptical that LifeKit’s “predictive power would hold up when applied to larger datasets, and argued that in the absence of better validation, physicians should not use this type of testing."
Further, LifeKit has not been compared with established tools for opioid risk assessment. The Current Opioid Misuse Measure (COMM-9) and the Opioid Risk Tool (ORT) are both simple and familiar instruments for evaluating the major risk factors for opioid use disorder.
Both COMM-9 and ORT are very inexpensive, easy to use, and give results quickly. By contrast, a gene test is expensive and requires weeks to get results. It is not clear at this point if a gene test offers any advantages over these existing instruments.
Opioid addiction risk is at present more readily assessed using tools that are already available and understood. Prescient has developed a novel and intriguing new tool, but still must prove its reliability in clinical settings before the costs and risks of such a test can be justified.
For now it is probably premature to expect this kind of genetic testing to be as useful as it would need to be to be adopted clinically.
Roger Chriss lives with Ehlers Danlos syndrome and is a proud member of the Ehlers-Danlos Society. Roger is a technical consultant in Washington state, where he specializes in mathematics and research.
The information in this column should not be considered as professional medical advice, diagnosis or treatment. It is for informational purposes only and represents the author’s opinions alone. It does not inherently express or reflect the views, opinions and/or positions of Pain News Network.