Considerations before ordering genetic tests

Genetics is one of the fastest evolving areas in medicine. However, ordering tests and interpreting them can be daunting. Using a series of case studies, Jennifer Hand, M.D., associate professor of dermatology, Clinical Genomics, and Pediatrics at the Mayo Clinic, Rochester, Minn., shared considerations one should make before ordering genetic tests directly, or referring patients to specialist genetic centres for testing and support. She spoke Sunday at the Society for Pediatric Dermatology Annual Meeting in Austin, Texas.

When determining what test is needed, the patient’s level of cognitive function can indicate how much genetic error may be present. If cognitive function is highly impaired, karyotyping may show that large pieces of genetic material are compromised. If there is less cognitive dysfunction, deletions or duplications may be implicated and detectable using chromosomal microarray, which can pick up congenital disorders, developmental delays and autism. If the patient is functioning well, then a single gene may be involved, so multigene panel testing may be the way to go.

When ordering tests directly, it is important to not only consider whether the test being ordered is the right one for the condition, but whether the patient’s insurance company will fund it.

“Insurance companies will sometimes only pay for one type of test using a certain technology, and you want to make sure you’ve got that right,” Dr. Hand says. Some labs will work directly with a patient’s insurance company and the main thing insurance companies want to know, she adds, is whether the mutation “actionable” - meaning, will it change the management of the patient or affect their outcome?

Interpretation
Interpreting the results report is rarely as simple as reading the top line, as it may contain other important information, such as other unmasked genes or variants of undetermined significance. She recommends dermatologists ordering tests read the full report to make sure that there is nothing that could be misinterpreted or confusing to the patient or the patient’s family.

A negative test result does not necessarily rule out a certain condition, she emphasizes, as both knowledge of genetics and available tests are growing all the time.

“When the test is negative, I usually recommend to the patient that they have periodic follow-up every two to three years,” she says.

While the United States has laws to prevent discrimination based on the results of a genetic test in employment and health insurance, this is not the case for life insurance discrimination. Patients without life insurance should be warned and advised that if they were thinking of getting insurance or increasing coverage, they should do so before having a genetic test performed.

The American College of Medical Genetics is a good resource for finding local specialist support, such as chaplains, nutritionists, social workers and genetic counselors for patients and their families dealing with genetic issues.

However, referring to a specialist centre can have advantages in that a wide range of specialist support will be available on site, Dr. Hand says. In particular, they will have genetic counselors with the expertise to take in-depth family histories, answer complex questions and support families through unforeseen issues. These can include paternity being found not to as expected, which happens in one in ten cases, and handling informing and testing other family members at risk of a condition identified in a relative.

Dermatologists who suspect a genetic condition usually have an idea what it might be, and specifying that condition and any genes presumed to be implicated in the referral letter can help ensure that patients receive the most useful tests, Dr. Hand says. 

“Use your dermatology expertise to give as many details about the type of testing that you want,” Dr. Hand advises.