Quantitation of red cell-bound IgG by an enzyme-linked antiglobulin test in the patients with warm-type autoimmune haemolytic anaemia.

We have previously reported the evaluation of a gel-direct antiglobulin test and enzyme-linked antiglobulin test (ELAT) in the laboratory diagnosis of autoimmune haemolytic anaemia (AIHA). We now report our experience with quantitative ELAT performed on a large group of patients under long-term observation. The number of IgG molecules/red blood cell was determined in 658 blood samples from 268 randomly selected patients with warm-type AIHA. Eighty-six patients were tested every 2-4 weeks for several months. Laboratory signs of haemolysis were present in 65.7% of blood samples with a small amount of red cell-bound autoantibody (< 200 IgG molecules/red blood cell) and in 70.4% of blood samples with moderately coated red blood cells (200-1000 molecules/red blood cell). Haemolysis was demonstrated in 87.9% samples with > 1000 IgG molecules/red blood cell, which were predominantly IgG3 and C3 complement, the qualitative factors that may increase haemolysis. In 79% of periodically tested patients, the number of IgG autoantibody molecules/red blood cell decreased and this correlated with the improvement of haemolysis parameters. The number of IgG molecules varied in 21% of AIHAs and was associated with poor prognosis.

Gel test application for IgG subclass detection in auto-immune haemolytic anaemia.

BACKGROUND AND OBJECTIVES: Commercially available gel test microtubes are not available with antisera for the determination of IgG subclasses. The aim of this study was to adapt the gel technique for this purpose and apply it to the investigation of patients with autoimmune haemolytic anaemia (AIHA). MATERIALS AND METHODS: We studied 66 red cell samples from 49 patients with AIHA of the warm-active IgG type. Standard serologic and haematologic methods were used. We adapted the DiaMed gel 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 those that were 'Coombs-negative', with less than 200 IgG molecules bound in vivo per red cell. Comparison of the gel test with the standard spin tube test and the microtiter plate test showed the superiority of the gel test, i.e., detection of IgG subclasses was much better than with the tube test and the results were more clearcut than those of the microplate test. The gel test is also the simplest and least time-consuming and permits a later reading of results. Application of the test in our 66 samples confirmed that IgG1 was the most frequent (96%). In 59% of the cases it was accompanied by IgG of other subclasses. Multiple subclasses were most common in the cases with stronger in vivo IgG red cell sensitization and severe haemolysis. Accompanying IgG3 was detected only in patients with obvious haemolysis. CONCLUSION: The gel test is more sensitive than other procedures for the determination of IgG subclass and has the advantages of simplicity, rapidity, low cost, and stability of the agglutinates.

Evaluation of the microcolumn technology for pretransfusion testing in multiple myeloma patients.

OBJECTIVE: Microcolumn tests are useful for serological investigations, although because of their high sensitivity, false-positive results might be expected, e.g. in hypergammaglobulinemia. The aim of this study was to evaluate these tests in multiple myeloma. METHODS: Pretransfusion testing was done in 80 patients with multiple myeloma using microcolumn and traditional tube tests. RESULTS: All sera were negative in microcolumn indirect antiglobulin test and enzyme test, positive in 58% of samples in the enzyme tube test. The microcolumn direct antiglobulin test was positive in about 40% of samples but never in the tube direct antiglobulin test. This was not due to the presence of autoantibodies but to nonspecific binding of immunoglobulins related to their concentration in sera. CONCLUSION: Microcolumn tests appeared to be useful for pretransfusion testing in multiple myeloma in spite of positive autocontrols.