Systematic review of 57 studies finds 144 blood biomarkers that differ in adults with Long COVID
A review in BMC Infectious Diseases found 144 serum and plasma biomarkers that differed between Long COVID patients and controls. IL-6, TNF-α, IL-1β and CRP were most often elevated.
A systematic review of 57 peer-reviewed studies identified 144 blood-based biomarkers that differed significantly between adults with Long COVID and comparison groups. The work was published in BMC Infectious Diseases by Lai and colleagues in 2026 biomedcentral.com
BMC Infectious Diseasesbiomedcentral.comOpen source ↗. Clinicians currently lack a validated biomarker-based approach to classify patients with Long COVID, which, according to the authors, limits standardized evaluation, treatment planning and follow-up.
The authors searched PubMed, CINAHL and Embase. Eligible studies included adults with Long COVID and either healthy donors or individuals who had recovered from infection without Long COVID. Each study had to provide extractable biomarker data measured in serum or plasma.
Comparison with healthy donors
Thirty-one studies compared Long COVID patients with healthy donors. Among them, four reported elevated C-reactive protein (CRP), and four reported elevated tumor necrosis factor alpha (TNF-α). The summary does not specify whether these were the same four studies.
Comparison with recovered individuals
Thirty-six studies compared Long COVID patients with recovered individuals without Long COVID. In this group, interleukin-6 (IL-6) was the most frequently reported elevated marker, in six studies. TNF-α was reported as elevated in five studies, while interleukin-1 beta (IL-1β) and CRP were each reported in four studies biomedcentral.com
BMC Infectious Diseasesbiomedcentral.comOpen source ↗.
According to the authors, these findings are consistent with recurrent inflammatory abnormalities in subsets of people with Long COVID. The review concerns differences in group-level biomarker measurements reported in earlier studies and does not offer a diagnostic test.
Proposed framework
Building on these results and their previous review, the authors propose a candidate framework for prioritizing both routinely available and exploratory biomarkers. They state that the markers require longitudinal and prospective clinical validation. Until such validation is done, the framework remains a proposal for further study rather than a tool for routine clinical evaluation.
