Significance of determining concentrations of subclasses of IgG and IgA: Our experience

Abstract

Selective IgG and IgA subclass (IgGsc and IgAsc) deficiencies may be either partial or complete, yet, combined subclass deficiencies are common. The serums of 65 patients with various clinical symptoms were investigated for quantitative and qualitative immunoglobulin levels. A high correlation (r=0.93) between the two methods used for measuring total IgG concentration (nephelometry) and IgGsc concentration (RID measurement) was demonstrated. Patients were divided into groups according to IgG and IgA class and subclass concentrations. The serums of 51 patients were investigated for IgGsc deficiencies. Three groups were set up and studied: a group with decreased IgG concentrations (5 patients), a group with elevated IgG concentrations (6 patients), and a group with normal IgG concentrations (40 patients). Within these groups, a total of 14 patients with decreased IgGsc levels and 14 patients with elevated IgGsc levels were discovered. Analyses of gender and age frequency within these groups showed that there were significantly (p<0.025) more children and females in the group with the elevated IgGsc concentrations, IgG2 being the most frequent. IgG1 deficiency was found to be more frequent in the group with decreased total IgG compared to the group with normal total IgG. We found IgGsc deficiency to be significantly associated (43%) with IgAsc deficiency within our population, therefore we recommend IgAsc concentration measurement in all patients with IgGsc deficiency. We confirmed that IgGsc concentrations should be measured in all patients with clinical symptoms and decreased total IgG concentrations and even more so in patients with normal total IgG concentrations. So far, we have not investigated our healthy population, and have not obtained our own reference ranges of IgGsc concentrations for children and adults. Therefore, the results we gained are yet to be explained, since, preliminary analysis shows elevated IgG2sc concentrations, and others to a lesser extent, in our population of children.