University Publications

<p><strong>Background:</strong> The differentiation between fresh and long -standing infections is one of the greatest challenges in serology. Until now this was based mainly on determination of specific antibodies of the immunoglobulin class IgM,which generally only appear initially.However,the detection of these antibodies is often unreliable and problematic due to interfering factors such as persistence of the IgM response, too weak or delayed IgM production and unspecific IgM production through polyclonal B-cell stimulation. In recent years additional determination of the antibody avidity has become an established method for identification of primary infections. The immune system reacts to an infection by first forming low avidity antibodies. With continued disease duration, IgG that are more precisely adapted to the antigens are produced-the avidity increases. The aim of this study to diagnose primary Rubella infection by determining Rubella immunoglobulin G (IgG) avidity index.</p> <p><strong>Methods:</strong> Retrospectively fifty samples with positive rubella IgG were tested for the functional IgG affinity, using the (Euroimmun rubella IgG avidity kit, Germen). By using indirect ELISA, the test was performed according to manufactures instructions, in which each diluted sample or control was pipetted into two adjacent wells (one well with urea and another well with phosphate buffer) which measured the avidity utilizing urea as a denaturing agent.</p> <p><strong>Result:</strong> Among the fifty IgG positive sera for rubella, IgM +ve was 40(80%) and IgM -ve was 10(20%) were studied for the IgG avidity, then 37(74%) sera were found to have high avidity IgG(RAI &gt; 60%), beside 13(26%) revealed low IgG avidity (RAI &lt; 40%).</p> <p><strong>Conclusions:</strong> IgM result interpretation is a problematic task, which is now hoped to be relieved by parallel IgG avidity testing.</p>