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IgG Subclass Concentrations in Certified Reference Material 470 and Reference Values for Children and Adults Determined with The Binding Site Reagents

¹ Klinik für Kinder- und Jugendmedizin der Ruhr Universität Bochum, D- 44791 Bochum, Germany.

² Universitätskinderklinik Leipzig, D-04103 Leipzig, Germany.

³ Altonaer Kinderkrankenhaus Hamburg, D-22763 Hamburg, Germany.

⁴ Institut für Klinische Chemie und Molekulare Diagnostik, Philipps Universität Marburg, D-35033 Marburg, Germany.

⁵ Institut für Klinische Chemie Grosshadern, Klinikum der Universität München, D-81377 Munich, Germany.

⁶ The Binding Site Ltd, Birmingham, B29 6AT, UK.

⁷ Department of Immunology, University of Birmingham, Birmingham, B15 2TT, UK.

⁸ The Binding Site GmbH, D-69120 Heidelberg, Germany.

^aAddress correspondence to this author at: Klinik für Kinder- und Jugendmedizin der Ruhr Universität Bochum, St. Josef-Hospital, Alexandrinenstrasse 5, D-44791 Bochum, Germany. Fax 49-234-509-2612; e-mail uwe.schauer{at}ruhr-uni-bochum.de.

Background: There is currently no international reference preparation for IgG subclass (IgGSc) quantification. This situation has led to calibration differences among assays and a variety of reference interval values with consequential difficulties in comparing results. We therefore evaluated IgGSc concentrations in Certified Reference Material 470 (CRM 470).

Methods: Pure, polyclonal IgG1, -2, -3, and -4 were prepared from a large serum pool for use as primary standards. The IgG mass in each preparation was calculated from amino-acid analysis data. IgGSc concentrations were assessed in CRM 470 by nephelometry with modern analytical techniques, using these reference preparations. Subsequently, IgGSc concentrations were measured in 380 healthy individuals (250 males and 130 females), and age-dependent reference intervals were established.

Results: IgGSc concentrations in CRM 470 were as follows: IgG1, 5028 mg/L; IgG2, 3418 mg/L; IgG3, 579 mg/L, and IgG4, 381 mg/L, with a total IgG concentration of 9406 mg/L, 2.83% below the certified total IgG value of 9680 mg/L. Age-dependent percentile curves for the four IgGSc were constructed using a Box–Cox transformation. Maximum median values were as follows: IgG1, 6.02 g/L at 11 years; IgG2, 3.45 g/L at 31 years; IgG3, 0.63 g/L at 17 years; and IgG4, 0.48 g/L at 14 years. No significant sex-related differences were observed.

Conclusions: The correlation between the summation of individual IgGSc and separate measurements of total IgG concentrations was good and supports the accuracy of the results. The results are based on The Binding Site assays and should not be considered appropriate for other assays unless so demonstrated.