In the development of the sensitive single molecule array (SIMOA) technology, serum and blood plasma from EDTA collection tubes were used to verify and validate blood levels of NFL, GFAP, Tau and UCHL1 across healthy controls[1]. As the need arises to establish extensive baseline levels of these neurobiomarkers in order to better evaluate neurodegeneration in a wide variety of patients including multiple sclerosis (MS) patients, a validation study across a variety of blood collection anticoagulants is necessary to ensure there are no significant differences in blood levels due to the additives themselves.
To determine whether SIMOA results are reliable and comparable within patients and between cohorts, we measured blood levels of the neurobiomarkers neurofilament (NFL), glial fibrillary acidic protein (GFAP), tau and ubiquitin C-terminal hydrolase L1 (UCHL1) in samples collected with different blood collection additives.
Serum and blood plasma were collected voluntarily from either headache or healthy control patients in one of four different blood collection tubes representing the 4 most common types of anticoagulant: none (serum), EDTA, sodium heparin (hep) and sodium citrate (NaC). Plasma and serum were isolated from whole blood by centrifugation at 1500 x g for 20 minutes. Plasma was centrifuged at 400 x g for 10 minutes to further deplete cells. Biomarker levels of NFL, GFAP, Tau and UCHL1 were measured via SIMOA with the Neuro4Plex A Advantage kit in the Quanterix SR-X machine according to manufacturer instructions. Statistical comparisons were made using GraphPad Prism analysis software.
No statistically significant differences in blood concentrations were found between the anticoagulants for the NFL, GFAP or UCHL1 biomarkers in either the headache patients or the healthy control patients. However, Tau levels were significantly lower in all serum samples (p value <0.0001) from both patient cohorts with average levels 65-80% lower than plasma.
Use of serum should be avoided when establishing baseline blood levels of the neurobiomarker Tau on the SIMOA platform.