ABSTRACT
【Objective】 To establish and evaluate a nephelometric assay for the determination of immunoglobulin A (IgA) residues in human intravenous immunoglobulin(IVIG). 【Methods】 BN ProSpec© automatic protein analyzer and its supporting immunoglobulin A determination kit (nephelometry) produced by German Siemens and the national standard of human IgA were used to establish the nephelometric assay to determine IgA residue in test products and verify the methodology. The test products include IVIG (pH4) prepared by low-temperature ethanol protein separation process and a novel IVIG prepared by chromatography. 【Results】 The average deviation of three calibration curves for IgA residues determination by the nephelometric assay were 1.08%, 0.95% and 1.54%,, and the three deviations of the quality control were 4.00%, -2.30% and -0.20%, respectively, which indicated good calibration and quality control. In the specificity test, the average recovery rates of IgA for reference substance 1 containing 100g/L maltose and reference substance 2 containing 20g/L glycine were 102.7% and 105.8%, respectively. The relative standard deviation (RSD) values of the repeatability tests of the two test products were 3.9% and 1.9%, and the RSD values of the intermediate precision test were 3.6% and 2.3%, respectively.The difference values at each time point in the durability test of test products′ storage time were all less than 10%, and the RSD values of the two test products in the durability test of kits of different batches were 2.8% and 2.2%, respectively. In the accuracy test, the average recovery rates of IVIG (pH4) added to the standard were 94.2%, 101.7% and 96.2%, respectively, and the average recovery rates of the novel IVIG added to the standard were 102.8%, 106.3% and 99.7%, respectively. The average recovery rate of the limit quantification test was 101.0%, and the RSD was 4.0%. 【Conclusion】 Nephelometric assay has the advantages of strong specificity, high precision and accuracy, good repeatability, simple and rapid operation, and automation, and can be used for the determination of IgA residue in IVIG (pH4) and novel IVIG products.