Comparación de dos métodos para la cuantificación en suero de subclases de inmunoglobulinas

Background and aim

The quantification of serum immunoglobulins, and particularly of IgG and IgG subclasses, is of interest for the diagnosis of numerous diseases. The usual detection methods provide different results according to the analyser used. The aim of this study was to compare the results obtained with two different analysers in the measurement of the concentration of IgG and IgG subclasses.

Material and methods

A total of 116 serum samples, regardless of the clinical diagnosis of the patients to whom the samples belonged, were analysed. The analyses were performed on a BNII^® System (Siemens Healthcare GmbH, Germany) and Optilite^® system (The Binding Site Group Ltd., Birmingham).

Results

The correlation between total IgG concentration (mg/dl) and the sum of the individual IgG subclasses detected was higher using the Optilite^® analyser (0.976 vs. 0.866). The percentage of agreement between assays ranged from 43% to 71%, with the lower limit being for the IgG3 agreement. An absence of the usual IgG subclass physiological proportion (IgG1 >IgG2 >IgG3 >IgG4) was detected using BNII^®. These findings were a due to the significantly lower proportion of IgG3 obtained by BNII^® compared to Optilite^® (P< .001), whereas the IgG4 concentration was not significantly different between analysers (P = .117).

Conclusions

Differences between the results obtained with the two different methods suggest that they should not be interchangeable, and that each clinical laboratory should only use one type of analyser. The reference ranges should be standardised according to the results obtained.