If the sum of IgG1-4 differs by >20% from the total IgG concentration, the assays are repeated at higher dilutions to rule out antigen excess.
We conclude that the quantification of IgG subclasses by LC-MS/MS using isotope-labeled ISs specific for each subclass or a surrogate digestion standard (horse IgG) has similar performance to current nephelometric-based assays and is not subject to antigen excess artifacts.
This experience prompted us to further investigate the incidence of serum FLC antigen excess.
Some nephelometers, including the BN II, have automated detection algorithms designed to detect antigen excess.
0 mg/L), a total imprecision study (total CVs <10%), antigen excess
detection (tested up to 50 g/L), analytical recovery near 100%, and parallelism between polyclonal and monoclonal FLCs within the analytical ranges.
In conclusion, an effective and efficient procedure for the detection of antigen excess
could be included in the assay for urinary albumin on the Roche Modular analyzer and could eliminate the need for additional tests to prevent reporting of falsely low results from antigen excess
Furthermore, this simple prozone detection method can be adapted to other nephelometric assays with the potential for erroneous results from antigen excess
Because of potential problems in the assay of MC, especially problems due to antigen excess
(6), we compared the results of assays of non-MC-containing samples and of MC-containing samples separately, as well as the overall results (Fig.
This led us to devise a new method with particle-enhanced turbidimetric inhibition, where antigen excess
would not be a problem but good assay imprecision at the upper limit of the reference range could be achieved.