Immunoassay for the qualitative determination of IgM-antibodies against CMV
Cytomegalovirus (CMV) is a herpes virus ubiquitous in humans, and it is the leading infectious cause of congenital malformations1. The global prevalence ranges from 40 to 60 % in Western industrialized countries and from 80 to 100 % in low-resource rural areas and developing countries2.
CMV is transmitted by direct contact of mucous membranes with infectious body fluids, but transmission can also occur following transfusion of blood products and transplantation of organs from seropositive donors3. In healthy individuals acute infection is mostly subclinical or asymptomatic and turns latent.4 Reactivation in immunocompromised people is frequently associated with severe clinical consequences.4 Vertical transmission occurs from an infected mother to the fetus during pregnancy.4 Due to latency following primary infection and periodic reactivation of CMV replication causing recurrent infections, in utero transmission of CMV may follow either primary or recurrent infections.4 Consequences include severe fetal damage, growth and mental retardations, jaundice and CNS abnormalities. If unsuspicious at birth, hearing defects or cognitive deficits may develop later in life.4
There is currently no generally accepted therapy available4, but recent scientific evidences showed that antiviral medication can reduce the risk of vertical transmission, making the screening and treatment of cytomegalovirus in pregnancy to protect the unborn baby's health finally an available option.5 The diagnosis of CMV infection usually starts with the detection of anti-CMV IgG and IgM antibodies, and IgG avidity test to determine the age of the infection. Samples being reactive for CMV IgM antibodies indicate an acute, recent or reactivated infection. A positive IgM result in combination with a low avidity index for IgG detected before the 16th – 18th week of pregnancy is an indication of a primary CMV infection within the preceding 3 to 4 months, whereas high avidity during the first 12 – 16 weeks excludes primary infection within the preceding 3 months4.