Comparability evaluation of serum and plasma cytokine levels by multiplex bead-based flow cytometry

Serum and plasma are the most common matrices for cytokine assays. Nevertheless, there is a lack of comparability evaluation for cytokine levels in two matrices based on multiplex bead-based flow cytometry. The study aimed to evaluate the comparability of IL-6, IL-8, and IL-10 serum- and plasma-based measurement results using flow cytometry.

The serum and EDTA-K₂ plasma were collected from three cohorts of hematologic malignancy patients (n = 66, 75, and 37, respectively) to evaluate comparability of IL-6, IL-8, and IL-10 measurement results using QuantoBio 14-plex cytokine kit on the BeamCyte-1026 flow cytometry. The Passing-Bablok regression was performed between serum- and plasma-based levels of cytokines. Additionally, the relative deviation of cytokine measurement results from the two matrices was compared with the allowable limits from the China National External Quality Assessment cytokine program.

The results revealed a relatively high correlation in IL-6, IL-8, and IL-10 levels between serum and plasma, with correlation coefficients of 0.966, 0.924, and 0.985, respectively. However, the comparability in the two matrices was unsatisfactory. Compared to plasma, the relative deviation of IL-6, IL-8, and IL-10 in serum was 74.8 %, -29.3 %, and 46.5 %, respectively, and only 20 % (IL-6), 31 % (IL-8), and 38 % (IL-10) of samples met allowable limits.

Poor comparability was found between serum- and plasma-based measurement results. Moreover, given the great potential of cytokine profiling in diagnosing and treating diseases, there is an urgent need to develop accurate and consistent processing of samples of cytokine assays to improve the accuracy and reproducibility of results and ensure the specimen's fitness for purpose.