Clinical studies show that new ‘cell-free’ test can predict cardiovascular disease risk better than standard HDL cholesterol test
Researchers from the National Institutes of Health (NIH) have developed a diagnostic assay that measures how well high-density lipoprotein (HDL)—the so-called “good” cholesterol—is working in the body. And their findings could lead to new clinical laboratory tests that supplement standard HDL level testing to better determine a person’s risk for heart disease.
Cholesterol tests are among the most commonly performed assays by clinical laboratories. A new test that reveals how well HDL is working in the body would certainly boost a medical laboratory’s test requisition volume.
The researchers are with the NIH’s National Heart, Lung, and Blood Institute (NHLBI).
“Measuring HDL function is limited to research labs and isn’t conducive to large-scale testing by routine clinical laboratories. To try to solve that problem, researchers from NHLBI’s Lipoprotein Metabolism Laboratory created a new diagnostic test,” noted an NHLBI news release.
“This is going to quicken the pace of basic research,” said Edward B. Neufeld, PhD, who along with guest researcher Masaki Sato, PhD, developed the test. “It increases the number of samples that you can study. It increases the number of experiments you can do.”
The researchers published their findings in The Journal of Clinical Investigation titled, “Cell-Free, High-Density Lipoprotein–Specific Phospholipid Efflux Assay Predicts Incident Cardiovascular Disease.” They have also patented their test and plan to work with a company on licensing and manufacturing it.
Such a new cholesterol test would quickly become one of the most commonly performed clinical lab tests because just about every American who has a physical gets cholesterol tests as part of that process.
“Other people may modify this or come up with better versions, which is fine with us,” Edward Neufeld, PhD (above), NHLBI Staff Scientist, said in a news release. “We just really wanted to tackle this problem of evaluating HDL function.” Clinical laboratories may soon have a new cholesterol test to supplement standard HDL level testing. (Photo copyright: ResearchGate.)
Faster Answers Needed about HDL
According to the NIH, the goal should go beyond measuring level of HDL as part of a person’s annual physical. What is also needed is finding out whether HDL cholesterol is effectively doing certain tasks, such as removing extra cholesterol from arteries and transporting it to the liver.
The NHLBI’s new cell-free test may make it possible to step up large-scale clinical testing of HDL function, according to the news release. As it stands now, HDL function study has been limited to research labs where testing involves “harvesting cells in the lab [which] can take days to process,” according to NIH Record.
“Most studies to date that have assessed CAD (coronary artery disease) risk by HDL functionality still use the CEC (cellular cholesterol efflux capacity) in vitro assay and are based on the use of radioisotopes (3H-cholesterol) and cultured cells, which is very labor intensive and impractical to do in a clinical laboratory,” the researchers wrote in The Journal of Clinical Investigation. They also pointed out that CEC batch-to-batch variability does not fit clinical laboratories’ need for standardization.
Advantages of NHLBI’s Test
To overcome these barriers, the NHLBI researchers created an HDL-specific phospholipid efflux (HDL-SPE) assay that has certain advantages over current HDL function assessments done in research labs.
According to the NIH, the HDP-SPE assay:
- Is easy to replicate in clinical labs.
- Is more suited to automation and large samples.
- Offers up results in about an hour.
- Is a better predictor of cardiovascular disease risk than HDL cholesterol testing for CAD risk.
“We developed a cell-free, HDL-specific phospholipid efflux assay for the assessment of CAD risk on the basis of HDL functionality in whole plasma or serum. One of the main advantages of the HDL-SPE assay is that it can be readily automated, unlike the various CEC assays currently in use,” the authors noted in their paper.
Here is how the test is performed, according to the NIH:
- Plasma with HDL is separated from the patient’s blood.
- “Plasma is added to donor particles coated with a lipid mixture resembling plaque and a fluorescent-tagged phospholipid” that only HDL can remove.
- The fluorescent signal by HDL is then measured.
- A bright signal suggests optimal HDL lipid removal function, while a dim light means reduced function.
The test builds on the scientists’ previous findings and data. In creating the new assay they drew on data from:
- A study of 50 severe CAD and 50 non-CAD people.
- A Japanese study of 70 CAD and 154 non-CAD participants.
- Examined association of HDL-SPE with cardiovascular disease in a study of 340 patients and 340 controls.
“We have established the HDL-SPE assay for assessment of the functional ability of HDL to efflux phospholipids. Our combined data consistently show that our relatively simple HDL-SPE assay captures a pathophysiologically relevant parameter of HDL function that is at least equivalent to the CEC assay in its association with prevalent and incident CAD,” the researchers concluded in The Journal of Clinical Investigation.
Test May Be Subject to New FDA Rule
While HDL cardiovascular-related research is moving forward, studies aimed at the therapeutic side need to pick up, NIH noted.
“Someday we may have a drug that modulates HDL and turns out to be beneficial, but right now we don’t have that,” said Alan Remaley MD, PhD, NHLBI Senior Investigator and Head of the Lipoprotein Metabolism Laboratory, in the news release.
It may be years before the HDL-SPE test is used in medical settings, the researchers acknowledged, adding that more studies are needed with inclusion of different ethnicities.
Additionally, in light of the recently released US Food and Drug Administration (FDA) final rule on regulation of laboratory developed tests (LDT), the company licensed to bring the test to market may need to submit the HDL-SPE assay to the FDA for premarket review and clearance. That could lengthen the time required for the developers to comply with the FDA before the test is used by doctors and clinical laboratories in patient care.
—Donna Marie Pocius
Related Information:
FDA Takes Action Aimed at Helping Ensure Safety and Effectiveness of Laboratory Developed Tests