Relationship of IgG Avidity Index and IgM Levels for the Differential Diagnosis of Primary from Recurrent Cytomegalovirus Infections

Since the incidence of symptomatic congenital cytomegalovirus infection is low (~0.05%)and risk factors are not well defined, it is difficult to develop strategies for prevention. theaim of this study was to recognise the utility of specific immunoglobulin g avidity analysisfor distinguishing primary infection from past/recurrent infection.sera from 50 women with cytomegalovirus specific immunoglobulin m antibodieswithout proven seroconversion and infants born to these women were tested for presence ofimmunoglobulin m antibodies by commercial enzyme immunoassay.for cytomegalovirus specific immunoglobulin g avidity, sera were measured bycommercial kit according to manufacturer's recommendations.among 50 sera form mothers, 26 showed the presence of immunoglobulin m antibodiesout of which 15 had low avidity antibodies. out of 50 sera from children, 18 showed thepresence of immunoglobulin m antibodies. out of these 18 sera from children, 12 weresymptomatic, which all showed the presence of low avidity antibodies.the results showed that an avidity index (less than)40% and presence of immunoglobulin mantibodies is highly suggestive of a recent primary infection.