The use of proteotypic peptides along with liquid chromatography-tandem mass spectrometry (LC-MS/ MS), a technique that does not suffer from antigen excess
, has emerged as a useful tool for quantifying proteins (9-12).
In this particular case, the patient had extremely high [kappa] FLC concentrations that caused antigen excess
and an artifactually low reading before treatment.
In conclusion, we have illustrated that antigen excess
can cause falsely low serum FLC results with nephelometric techniques.
High-dose hook effect (prozone phenomenon or antigen excess
Dilution study results excluded antigen excess
and the presence of a prozone, but a serum total (bound and free) light chains (Dade Behring) showed a marked increase of [kappa] (20.2 g/L, RI 1.7-3.7 g/L) compared to [lambda] (1.13 g/L, RI 0.9-2.1 g/L), resulting in a total [kappa]:[lambda] ratio of 17.9 (RI 1.35-2.65).
Reaction kinetics, including antigen excess
, is monitored automatically for all measurement modes thereby reducing re-runs and manual handling of samples and reagents.
Both immunochemical methods were considered to be acceptable on the basis of the results of detection limit determinations (~5.0 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.
Falsely low concentrations are encountered regularly in immunoturbidimetric assays as a result of antigen excess
A limitation of IFE procedures is the prozone artifact caused by antigen excess
(19), a problem that is avoided with immunoblotting.