When many people hear the words "heart test," the first thoughts that come to mind may not have anything to do with the laboratory. They may think of tests such a CT heart scans, coronary calcium tests and carotid artery ultrasounds, for example. But the clinical laboratory does play a part in diagnosing, managing and now even preventing cardiovascular disease (CVD).
"Many people think of cardiovascular testing as being performed by a cardiologist," added Doug Harrington, MD, CEO of Aviir, Irvine, Calif. "People associate things like routine blood work with their doctor's office visits . but what people don't realize is that the clinical lab can provide doctors with all kinds of diagnostic information that can help identify a disease or to find early hints that you might be getting sick."
Diagnosing and Monitoring CVD
When it comes to diagnosing a patient with CVD, clinical laboratory professionals run cholesterol and biomarker testing for specific proteins associated with disease, Dr. Harrington explained. One example, he said, is troponin testing, a biomarker associated with specific heart conditions.
"These tests provide useful diagnostic information for physicians," Harrington told ADVANCE. "They can show doctors whether elements in the blood indicate that a heart attack has happened, or if other associated symptoms of CVD are present."
Cholesterol testing is also done to manage a patient's condition once it is determined that he or she has CVD. "The primary goal for monitoring a disease already identified in patients is to make sure they are taking appropriate and aggressive action to prevent a second event, for example, by lowering LDL cholesterol," Harrington noted.
Genetic Testing and Predicting CVD
The lab has been used for years to diagnose and manage CVD. But now health care innovations make it possible for laboratory professionals to possibly stop heart-related problems before they even become an issue for patients, thanks to genetic testing.
"Testing to predict CVD is focused on detecting elements associated with pre-disease states," Harrington explained. "These predictive tests look mainly for signs of inflammation."
Harrington's company Aviir provides two tests to help laboratory professionals alert patients to potential inflammation problems. One is the MIRISK 5-year risk score, which takes two lipid biomarkers, five clinical risk factors, and uses one of Aviir's algorithms to determine if patients are at a low, intermediate or high risk for developing CVD, he noted.
"If patients' test results is in an intermediate-risk score, we recommend they take the MIRISK VP test," Harrington added. "The test measures seven of the most powerfully predictive protein biomarkers associated with the presence of vulnerable plaque and enables identification of the vulnerable patient. This is an individual who is at a significantly increased risk of having a heart attack in the next five years. Vulnerable plaque rupture is responsible for 75 percent of all heart attacks."
The MIRISK VP also combines clinical risk factors such as age, sex and smoking status with an algorithm to calculate the patient's risk for a heart attack over the next five years, Harrington added.
An Exciting Field
For laboratory professionals interested in a career in genetics, becoming a genetic counselor (GV) is a possible career path-even if they have a special interest in cardiovascular testing.
Samantha Baxter, MS, CGC, is a senior genetic counselor at GeneDx in Gaithersburg, MD. As a genetic counselor, she's held two laboratory roles. She wrote cardiomyopathy genetic test results for 4 years. "My role was gathering information from various public and private databases about the mutations and variants found during the test and integrating that information with the patient's clinical diagnosis and family history in order to provide the most comprehensive genetic test result possible," she said.
Baxter currently works in the GeneDx marketing department developing patient and physician educational materials. "No matter where a GC is positioned in the genetic testing process, one of our main goals is to always ensure that the patient and physician understand the intricacies of genetics and are informed about the genetic test being performed," she explained.
At GeneDX, the company's cardiology test panels are performed by using next generation sequencing, Baxter said. "The presence of any potentially disease-associated sequence variants are confirmed by conventional dideoxy DNA sequence analysis," she added.
In addition, for those diseases where deletion and duplication testing is performed, they use a microarray-based gene copy number analysis to detect a deletion or duplication in one of the genes analyzed. "The exon array uses a custom-designed oligonucleotide array for comparative genomic hybridization with probes concentrated in the specific genes tested," Baxter noted. "This method allows detecting whole-gene deletions and duplications as well as small deletions and duplications of one or more exons." Each positive test result is confirmed by quantitative polymerase chain reaction, she added.
The Importance of Genetic Tests for CVD
It's key to understand that genetic testing for CVD isn't done as a preventive screen for everyone, Harrington said. "It is done if a patient exhibits symptoms consistent with a genetically heritable condition, or if a patient has a relative with a confirmed diagnosis," he said.
Physicians will only order a genetic test if they believe the patient displays the correct diagnostic criteria for that specific disease. "We then look at a genetic sample from the patient and look for mutations in genes associated with the specific disease," Harrington said. "If we find one, it provides useful diagnostic information to the physician about how to treat the patient, and allows familiar disease testing to be focused on the mutation identified in the first patient."
Genetic testing for CVD is especially important for targeted predictive testing in asymptomatic family members. "Most the of inherited arrhythmias and cardiomyopathies have reduced penetrance and variable expressivity, which can make it very difficult to identify at-risk family members based on clinical screening alone," Baxter said. ". Once a mutation has been identified in the affected individual, the other family members can be tested for that specific mutation found in their family member and they will receive a result which tells them that they either have the mutation or they don't."
Amanda Koehler is a freelance writer.