Objectives: Preliminary 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 methods: The 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.
Results: The 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.
Conclusions: Compared 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.
Copyright © 2012 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.