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What does a positive reaction to IgG antibodies, IgM to cytomegalovirus

Methods of laboratory diagnostics of cytomegalovirus infection (CMV) infection include serological reactions, which aim at the detection of antibodies to cytomegalovirus (CMV) or antigens in the blood of the examinee or other substrates (urine, cerebrospinal fluid, saliva, swabs from trachea and bronchus, smears from the urethra and vagina).

Working as serological reactions

Detection of antibodies in serum is based on the fact that they are in the lab (as well as in the body) tend to contact with the antigen of the causative agent for inactivation.

Thus, if in the laboratory there are reagents containing the labeled somehow antigen to cytomegalovirus, and then applying them to bind to the immunoglobulins in the serum, the amount "spent" antigens to quantify the antibody titre. Work direct methods of specific diagnostics.

антитела к цитомегаловирусу

Indirect methods for diagnosis of CMV infection are rarely used.

To perform analysis prior training non-specific:

  1. On an empty stomach (to prevent rapid coagulation of the blood (hungry minimum period of 4 hours).
  2. Better to 11 hours.
  3. Do not take alcohol before the study.
  4. On the day of delivery of the analysis it is advisable not to smoke.

What serological test used to detect antibodies to CMV

For the detection of antibodies to cytomegalovirus, you can use the following methods:

  • the reaction of binding complement (RAC);
  • the reaction immunofluorescence (RIF);
  • enzyme-linked immunosorbent assay (ELISA);
  • radiological solid-phase analysis;
  • immunobloting.

The last three types of serological tests have the highest specificity and sensitivity, therefore are used much more often than others. Describe the mechanism of action of each reaction will not, the main thing about them is that they are all aimed at the detection of immunoglobulin M, G and determination of their index of avidity.

Immunoglobulin M (anti-CMV-IgM) in a large number formed during the primary immune response (the body's response to infectious agent (or one of the serotypes), for the first time penetrated the body and caused disease).

The immunoglobulin G (anti-CMV-IgG after IgM are synthesized, causing "memory immunity against the specific serotype of the pathogen. When re-infection by the same organism (same serotype), the human immune system responds by production of IgG in a large number.

Next, you need to decipher the concept of the index of avidity of antibodies to cytomegalovirus, as well as its importance in laboratory diagnosis of this infection.Avidity is the ability of immunoglobulins to firmly connect with the antigens of the virus CMV. And the index of avidity (IA) is an index that measures the degree of bond strength between antibody and antigen. Mention of CMV infection, to clarify the extent of its activity using the index of the avidity of immunoglobulin G (anti-CMV-IgG). The avidity of IgM is determined.

The decoding results of the survey

  1. If serum immunoglobulin M (anti-CMV-IgM) in any titer (say, IgM-CMV positive), then the examinee in question are diagnosed with primary cytomegalovirus infection. Further laboratory diagnosis is aimed at identification of antibodies of class G (anti of CMV-IgG) and the virus by PCR and/or DNA hybridization.
  2. The positive results of detection of IgG against cytomegalovirus are treated differently. In the table below are discussed in detail various options for positive serological reactions for cytomegalovirus.
  3. To prevent overdiagnosis options CMV infection often use the "method of paired sera". Its essence is twofold to determine levels of IgG and IgM with an interval of 2-3 weeks between blood draws. If quantitative content of immunoglobulins increases 4 times or more, the probability of acute (active) CMV infection in the examined high.
  4. Additionally I want to point to the fact that the quantitative values in a single study, the serum don't really matter. Typically, a significant quantity of antibodies begins with the titer of 1:100 and above (in different laboratories, the threshold value may vary).
IgM IgG Decoding of the result
Negative Negative The person is not infected with CMV and have never had contact with him, the other option is poor or unsuitable reagents
Positive, the index of avidity (IA) high, its value is above 42%, if the titles in the dynamics of growing 4 times more likely activation of "dormant" in the body of the infection Surveyed once for 6-12 months. ago and more) had cytomegalovirus infection
Positive, Eeyore is low, the value of it to 41% The probable error of diagnosis, repeat in 2 weeks
Positive Negative Likely the initial stage of CMV infection, when IgG haven't started to be synthesized (the first week of the disease), the second option – the error diagnostics should be repeated after 2 weeks, in addition to performPCR
Positive IA less than and equal to 35%, increase the credits to 4 times or more In the acute stage (active stage) CMV infection, control after 2 weeks
Positive, IA 36-41% The recovery stage
Positive, Eeyore, over 42% The so-called "tail" when surveyed after undergoing CMV infection IgM is stored, the second by the activation of "dormant" in the body of the infection, should conduct PCR of serum, if necessary – CSF

What are the diagnostic methods used to detect CMV antigens

At the end of the article it should be noted that for verifizierung the diagnosis of CMV infection not only the detection of antibodies to the virus, it is also important to confirm the presence of certain antigens or DNA of CMV in the blood (if necessary, in cerebrospinal fluid (CSF). If DNA or antigens found in saliva, urine, this is not indicative of the activity of CMV infection. Basic laboratory methods that can confirm the presence of antigens (or DNA) CMV – PCR and DNA hybridization.

Also read about diagnosis of CMV infection can and here.


  1. Diagnosis, treatment and prevention of cytomegalovirus infection in pregnant women. V. N. Kuzmin. The magazine "doctor", 11, 2002.
  2. Cytomegalovirus infection. V. F. Uchaikin, And L. N. Guseva. Department of pediatric infectious diseases, faculty of Pediatrics with the course of the vaccinal prevention Department, Russian state medical University.
  3. Clinical and laboratory characteristics of persistent forms of herpes-viral infections in children. Z. I. Pirogov, F. N. Ryabchuk. The magazine "doctor", 8/10.