Validation of a Highly Sensitive Immunoassay for the Quantitation of Interferon Beta in Autoimmune Sera

Authors: P.R. Conliff¹, T.M. Stauffer²; S.F. Bungo¹; M. Skawinski²; T. Lavoie²; I.S. DuBey¹

Author Affiliation: 1. Smithers Avanza; 2. PBL Assay Science

Purpose:

The role of interferons (IFN) in autoimmune disease is crucial to understanding the etiology and treatment of these diseases.

A highly sensitive immunoassay was validated and utilized for the quantitation of interferon beta in autoimmune sera.

Methods:

VeriKine-HS Human Interferon Beta Serum ELISA Kit was validated in 100% sample matrix. The lower limit of quantitation (LLOQ) was determined using independent spikes in pooled normal sera. Quantitation of endogenous levels in normal human and autoimmune patient sera as well as spike recovery were performed. Specificity against IFN Alpha, IFN Gamma and IFN Omega was assessed up to 10 ng/ml and assay response in the presence of hemolysis examined. Finally, multiple sclerosis (MS) samples measured across two sites and different lots of kits were correlated.

Results:

The methods were validated with an analytical range of 2.34 - 150 pg/ml and showed dilutional linearity up to 1:2187. Interassay precision (CV) was ≤13.1% with a mean % bias 17.1. The LLOQ of the assay was determined to be 2.34 pg/ml. No IFN Beta was detected in normal sera. Median quantifiable IFN Beta levels were 17.3 pg/ml in MS sera (n=47), with 26 quantifiable sera and 21 below LLOQ. One hundred percent (100%) specificity was demonstrated against IFN Alpha, IFN Gamma and IFN Omega in both blank matrix and matrix spiked with 60 pg/ml IFN Beta. Whereas no interference was detected up to 120 pg/ml IFN Beta at 10% hemolysis, a 23.2% bias at 100% hemolysis was observed at 120 pg/ml. MS samples showed excellent correlation (r²=0.9975) which is indicative of a robust and reproducible assay.

Conclusion:

A precise and accurate method was validated for measuring IFN Beta. These evaluations confirm that this highly sensitive immunoassay is suitable for evaluation of autoimmune sera.

(Click image below to download a PDF)