GEL TEST APPLICATION FOR IGG SUBCLASS DETECTION IN AUTOIMMUNE HEMOLYTIC-ANEMIA

Background and objectives: Commercially available gel test microtubes are not available with antisera for the determination of IgG subclasse s. The aim of this study was to adapt the gel technique for this purpo se and apply it to the investigation of patients with autoimmune haemo lytic anaemia (AIHA). Materials and methods: We studied 66 red cell sa mples from 49 patients with AIHA of the warm-active IgG type. Standard serologic and haematologic methods were used. We adapted the DiaMed g el test by using IgG-subclass antisera. Results: We found the adapted test useful in determining the subclass of autoantibodies in eluates. We could identify the IgG subclass in all the AIHA patients, even thos e that were 'Coombs-negative', with less than 200 IgG molecules bound in vivo per red cell. Comparison of the gel test with the standard spi n tube test and the microtiter plate test showed the superiority of th e gel test, i.e., detection of IgG subclasses was much better than wit h the tube test and the results were more clearcut than those of the m icroplate test. The gel test is also the simplest and least time-consu ming and permits a later reading of results. Application of the test i n our 66 samples confirmed that IgG1 was the most frequent (96%). In 5 9% of the cases it was accompanied by IgG of other subclasses. Multipl e subclasses were most common in the cases with stronger in vivo IgG r ed cell sensitization and severe haemolysis. Accompanying IgG3 was det ected only in patients with obvious haemolysis. Conclusion: The gel te st is more sensitive than other procedures for the determination of Ig G subclass and has the advantages of simplicity, rapidity, low cost, a nd stability of the agglutinates.