Open AccessSimilar but not consistent: Revisiting the pitfalls of measuring IgG subclasses with different assays
Author(s) -
LudwigKraus Beatrice,
Kraus Frank Bernhard
Publication year - 2017
Publication title -
journal of clinical laboratory analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.536
H-Index - 50
eISSN - 1098-2825
pISSN - 0887-8013
DOI - 10.1002/jcla.22146
Subject(s) - comparability , reference values , guideline , medicine , microbiology and biotechnology , chemistry , biology , mathematics , pathology , combinatorics
Background Laboratory quantification of IgG subclasses (Ig GS c) is a well‐established second‐line tool for differential diagnosis of immune deficiencies. However, so far there is still no internationally approved standard available for Ig GS c, and different assays are prone to produce divergent results. In this study, we evaluated the comparability and equivalence of two commercially available Ig GS c assays, one being the Siemens Ig GS c assay on a BN ProSpec analyzer and the other being The Binding Site ( TBS ) Ig GS c assay on a Roche cobas c502 analyzer. Methods We analyzed a total of 50 patient plasma samples obtained over a 3‐month period with both Ig GS c assays and compared the resulting data based and the CLSI EP 09‐A3 method comparison guideline. Results Depending on the analyzed Ig GS c type, the average relative differences in Ig GS c concentration (g/L) between the two assays were considerable, starting with −13.5% for IgG1 and 11.3% for IgG2, over −47.3% for IgG4, and up to 52.9% for IgG3. Applying the assay‐specific reference intervals, the classification agreement (below, within, or above the reference range) ranged from 88% to 90% for the individual subclasses. However, only 68% of samples showed an overall classification agreement. Conclusion The comparability of the two Ig GS c assays proved to be limited and might be considered similar at best on the diagnostic level. Laboratory specialists as well as clinicians therefore should be cautious when using and interpreting Ig GS c measurements obtained with different assays or analyzers.