The NIH’s Researching COVID to Enhance Recovery (RECOVER) Initiative used a cohort study of more than 10,000 individuals with and without previous COVID-19 diagnoses and compared samples using 25 common laboratory tests in hopes a useful biomarker could be identified. They were unsuccessful.
Long COVID—or PASC—is an umbrella term for those with persistent post-COVID infection symptoms that negatively impact quality of life. Though it affects millions worldwide and has been called a major public health burden, the NIH/Langone study scientists noted one glaring problem: PASC is defined differently in the major tests they studied. This makes consistent diagnoses difficult.
The study brought to light possible roadblocks that prevented biomarker identification.
“This study is an important step toward defining long COVID beyond any one individual symptom,” said study author Leora Horwitz, MD (above), director of the Center for Healthcare Innovation and Delivery Science and co-principal investigator for the RECOVER CSC at NYU Langone, in a Langone Health news release. “This definition—which may evolve over time—will serve as a critical foundation for scientific discovery and treatment design.” In the future, clinical laboratories may be tasked with finding combinations of routine and reference tests that, together, enable a more precise and earlier diagnosis of long COVID. (Photo copyright: Yale School of Medicine.)
NIH/Langone Study Details
“The study … examined 25 routinely used and standardized laboratory tests chosen based on availability across institutions, prior literature, and clinical experience. These tests were conducted prospectively in laboratories that are certified by the Clinical Laboratory Improvement Amendments (CLIA). The samples were collected from 10,094 RECOVER-Adult participants, representing a diverse cohort from all over the US,” Inside Precision Medicine reported.
However, the scientists found no clinical laboratory “value” among the 25 tests examined that “reliably indicate previous infection, PASC, or the particular cluster type of PASC,” Inside Precision Medicine noted, adding that “Although some minor differences in the results of specific laboratory tests attempted to differentiate between individuals with and without a history of infection, these findings were generally clinically meaningless.”
“In a cohort study of more than 10,000 participants with and without prior SARS-CoV-2 infection, we found no evidence that any of 25 routine clinical laboratory values provide a reliable biomarker of prior infection, PASC, or the specific type of PASC cluster. … Overall, no evidence was found that any of the 25 routine clinical laboratory values assessed in this study could serve as a clinically useful biomarker of PASC,” the study authors wrote in Annals of Internal Medicine.
In addition to a vague definition of PASC, the NIH/Langone researchers noted a few other potential problems identifying a biomarker from the research.
“Use of only selected biomarkers, choice of comparison groups, if any (people who have recovered from PASC or healthy control participants); duration of symptoms; types of symptoms or phenotypes; and patient population features, such as sex, age, race, vaccination status, comorbidities, and severity of initial infection,” could be a cause for ambiguous results, the scientists wrote.
Future Research
“Understanding the basic biological underpinnings of persistent symptoms after SARS-CoV-2 infection will likely require a rigorous focus on investigations beyond routine clinical laboratory studies (for example, transcriptomics, proteomics, metabolomics) to identify novel biomarkers,” the study authors wrote in Annals of Internal Medicine.
“Our challenge is to discover biomarkers that can help us quickly and accurately diagnose long COVID to ensure people struggling with this disease receive the most appropriate care as soon as possible,” said David Goff, MD, PhD, director of the division of cardiovascular sciences at the NIH’s National Heart, Lung, and Blood Institute, in an NHLBI news release. “Long COVID symptoms can prevent someone from returning to work or school, and may even make everyday tasks a burden, so the ability for rapid diagnosis is key.”
“Approximately one in 20 US adults reported persisting symptoms after COVID-19 in June 2024, with 1.4% reporting significant limitations,” the NIH/Langone scientists wrote in their published study.
Astute clinical laboratory scientists will recognize this as possible future diagnostic testing. There is no shortage of need.
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.
“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.”
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.
