Here are papers which say they have found a test which correlates well with Long COVID:
- 20210709: Reduced blood flow to retina.
- 20210729: Stiffer red blood cells.
- 20220401: Elevated levels of C-reactive protein, serum amyloid A, and vascular endothelial growth factor in cerebro-spinal fluid.
- 20220421: RNA in poo.
- 20220501: Viral antigens in the gut.
- 20220502: Differences in gut flora in mice.
- 20220509: Fibrin(ogen) amyloid microclots and platelet hyperactivation.
- 20220510: Type II interferon signaling and canonical NF-κB signaling (particularly associated with TNF), were the most differentially enriched pathways.
- 20220511: Von Willebrand Factor (VWF) Antigen (Ag):ADAMTS13 ratio.
- 20220518: Ventilation Defects found with hyperpolarized Xenon-129 MRIs.
- 20220612: Elevated CCL11 cytokine.
- 20220616: Persistent circulating spike proteins.
- 20220617: Rise in rise in quinolinic acid and 3 Hydroxyanthranilic Acid in brain fog patients.
- 20220617: Changes in gut flora: higher Bacteroidetes and lower Firmicutes in MIS-C patients. (Okay, not exactly Long COVID, but not exactly not Long COVID either.)
- 20220622: Lower levels of acetate and butyrate in gut bacteria.
- 20220627: IL-2 release from T cells in response to SARS-CoV-2 peptides. Sensitivity 75%, specificity 88%.
- (oops, I apparently lost focus there)
- 20221213: Inflammatory mediators IFN-β, PTX3, IFN-γ, IFN-λ2/3 and IL-6