Analytical and Clinical Validation of an Automated Microfluidic Interleukin-6 Immunoassay

Objective. We validated an automated microfluidic interleukin-6 (IL-6) immunoassay on the Ella platform for clinical use. Methods. The assay was validated for precision, lower limit of quantification, analytical measurement range, accuracy, specificity, interference of biotin, tocilizumab, GP130, IL-6Rα, hemolysis, icterus, and lipemia, and establishing the reference value. The clinical performance was evaluated in 96 COVID-19 patients. Results. The within-run and between-run coefficient of variations (CV) ranged 1.8%-4.8%. This assay has an analytical measurement range (AMR) 0.7-2652 pg/ml. There was a moderate correlation between Ella IL-6 assay (y) and a Luminex Quantitative Multiplex Bead Assay in a reference lab (x): y=8.561x-475.38, R=0.5047, SEE=1592.8 pg/mL, N=48). Measurement of IL-6 in plasma samples from 45 healthy adults showed the upper limit of reference of 5.0 pg/mL. 95.83% (95% CI: 89.67%-98.85%) of COVID-19 patients had IL-6 >5.0 pg/mL. This assay is resistant to the interference from hemoglobin up to 1,144 mg/dL, triglyceride 1,699 mg/dL, bilirubin 35 mg/dL, biotin 1000 ng/mL, tocilizumab 240 µg/mL, IL-11 50,000 pg/mL, GP130 50,000 pg/mL, and IL-6Rα 1,000 pg/mL. Conclusions. The IL-6 assay on the Ella platform is robust with minimum manual operation. The analytical and clinical performance characteristics meet the clinical needs.