Evaluation of Eight Anti-rubella Immunoglobulin G Immunoassays that Report Results in International Units per Milliliter

National Serology Reference Laboratory, Australia, St. Vincent's Institute, 4th Floor, Healy Building, 41 Victoria Parade, Fitzroy 3065, Department of Serology, Symbion Health, Dorevitch Pathology, 18 Banksia Street, Heidelberg 3084, Centre for Infectious Diseases and Microbiology Laboratory Services, Institute of Clinical Pathology and Medical Research, Westmead Hospital, Westmead 2145, Microbiology Department, Southern Health, 246 Clayton Road, Clayton 3168, Department of Microbiology and Immunology, University of Melbourne, Parkville, 3052, Australia

^* To whom correspondence should be addressed. Email: wayne{at}nrl.gov.au.

	Abstract

An evaluation of anti-rubella immunoglobulin G immunoassays that report in International Units per milliliter (IU/mL) was performed to determine their analytical performance and the degree of correlation of the test results. A total of 321 samples were characterized based on results from a haemagglutination inhibition assay. The 48 negative and 273 positive samples were used to determine sensitivity and specificity of the assays. When equivocal results were interpreted as reactive, the sensitivity of the immunoassays ranged from 98.9 to 99.9% and the specificity from 77.1 to 95.8%. All assays had positive and negative delta values of less than 2. A significant difference between the mean results of all assays was demonstrated by an analysis of variance. However, Post Hoc analysis showed there was good correlation in the mean results expressed in IU/mL between some of the assays. Our results show the level of standardization between anti-rubella immunoglobulin G immunoassays reporting results expressed as IU/mL has improved since a previous study in 1992 but further improvement is required.