A recent study indicates that standard lab tests may not effectively aid in diagnosing long COVID in individuals showing symptoms. This research sheds light on the difficulties faced when trying to identify and diagnose a new illness like long COVID.
A study supported by the National Institutes of Health (NIH) reveals that routine laboratory tests might not be helpful in diagnosing long COVID for those experiencing related symptoms. This study is part of the NIH’s Researching COVID to Enhance Recovery (NIH RECOVER) Initiative and has been published in the Annals of Internal Medicine. It underscores the complexities of diagnosing a new condition like long COVID.
“Our challenge is to find biomarkers that will allow us to diagnose long COVID quickly and accurately, ensuring that those affected receive appropriate care as soon as possible,” stated David Goff, M.D., Ph.D., who leads the Division of Cardiovascular Sciences at NIH’s National Heart, Lung, and Blood Institute. “Long COVID symptoms can hinder individuals from returning to work or school and may even make daily activities challenging, so prompt diagnosis is crucial.”
Long COVID consists of a variety of symptoms and health issues that can persist for months or even years following infection with SARS-CoV-2, the virus responsible for COVID-19. Currently, there are no established clinical biomarkers for long COVID, necessitating a thorough medical history and physical examination to assess symptoms, alongside laboratory tests to exclude other potential causes.
The research aimed to evaluate whether a SARS-CoV-2 infection resulted in significant changes to biomarkers—like platelet counts or urine protein—when comparing individuals with a past infection to those without.
Between October 2021 and October 2023, over 10,000 adults from across the U.S. were recruited as part of the RECOVER Adult Cohort from 83 different sites. This cohort is demographically varied, with participants hailing from numerous geographic areas. Among the 8,746 participants who had previously been infected with SARS-CoV-2, many experienced different variants, while 1,348 had never contracted the virus.
The RECOVER Adult Cohort includes individuals both with and without previous SARS-CoV-2 infections, as well as those with and without long COVID. Nearly 19% of the participant group was identified with long COVID.
Study participants underwent an initial assessment that included surveys, a physical examination, and 25 standard lab tests for blood and urine. They were monitored over a two-year span, completing surveys every three months and undergoing lab tests at intervals of six, 12, 24, 36, and 48 months. The lab tests included a comprehensive blood count, metabolic panel, hemoglobin A1c (HbA1c), urinalysis, and urine albumin to creatinine ratio (uACR), among others.
According to the researchers, the lab tests revealed very few notable differences in biomarkers between previously infected individuals and those who were not infected. Nonetheless, they did observe minor increases in HbA1c, reflecting average blood sugar levels over the previous two to three months; however, these increases disappeared after excluding participants who had pre-existing diabetes.
Additionally, the researchers noted slight elevations in uACR—a measure indicative of kidney function—in individuals with past infections, but these increases were minor and appeared in only a few people in that group, potentially linked to the severity of their initial infection.
In a secondary analysis, the researchers concentrated exclusively on the infected group to compare differences between participants who developed long COVID and those who did not. Using a previously established long COVID index with 12 indicative symptoms, the study found no significant differences in lab test outcomes between the two sub-groups.
“Future research will utilize the RECOVER biobank of cohort samples, including blood and spinal fluid, to create more innovative laboratory tests aimed at enhancing our understanding of long COVID’s pathophysiology,” said Kristine Erlandson, M.D., a professor of medicine-infectious disease at the University of Colorado Anschutz Medical Campus in Aurora.
This research was funded by the NIH under award numbers OT2HL161841, OT2HL161847, and OT2HL156812, with additional support from grant R01 HL162373. The content represents the authors’ views and does not necessarily reflect the official opinions of the NIH. For further details about RECOVER, visit: https://recovercovid.org
