Assessment of the diagnostic performances of IgA heavy and light chain pairs in patients with IgA monoclonal gammopathy

ObjectivesPreliminary results of the IgA Hevylite™ assay including the establishment of the 95% reference interval and assessment of the specificity and sensitivity in different populations are reported.Design and methodsThe concentrations of IgA heavy and light chains (HLC) enabling to determine an IgAκ/IgAλ ratio were quantified in 119 apparently healthy individuals to generate 95% reference intervals. The specificity of this assay was assessed in 48 patients with an isolated polyclonal IgA increase. In a retrospective analysis of 68 patients with a monoclonal component type IgA (MC-IgA) identified by serum immunofixation (IFE), IgA HLC ratio values were compared with known results for serum protein electrophoresis (SPE) and free light chain (FLC) ratios.ResultsThe 95% reference range obtained in 119 controls (0.91–2.04) was close to that quoted by the manufacturer (0.80–2.04). Eight of the 48 patients (16.7%) with a polyclonal IgA increase had an IgA HLC ratio above the upper limit of the 95% reference interval.The IgA HLC ratio identified 65 (95.6%) among 68 patients with MC-IgA identified on the basis of IFE. For 34 of these patients (50%), MC-IgA was not detected by SPE due to its co-migration with alpha-2 or beta-globulins.ConclusionsCompared with serum IFE, the IgA HLC ratio has a sensitivity of 95.6%. Further studies are needed to assess the specificity of the IgA HLC ratio in patients with an isolated polyclonal increase of serum IgA.

► Evaluation of a new test for which few results are available in the literature
► Assessment of the clinical sensitivity of the test
► Assessment of reference range on healthy individuals
► Assessment of the analytical performance of the test (precision)
► Evaluation of the specificity of the test in case of polyclonal increases of IgA