What are the diagnostic methods of cytomegalovirus in blood, urine, smear
The main substrates for research:
- the serum of the blood (venous, it is necessary to take on an empty stomach possible empty interval of 4 hours;
- the CSF (cerebrospinal fluid);
- smears from the urethra and vagina, cervical canal;
- swabs from trachea and bronchial phlegm.
What methods are used to detect CMV
Among the huge number of methods designed to detect microorganisms from the patients, in the diagnosis of CMV infection are:
- RAC (reaction of complement binding);
- RIF (immunofluorescence reaction);
- ELISA (enzyme-linked immunosorbent assay);
- Radiological solid-phase analysis;
- DNA hybridization;
- Cultural method;
The latter method detects cytomegalovirus in a smear or slice based on the detection of "cytomegalic cells that have undergone morphological change under the impact of the virus. They have large externally memorable kernel. Often used for studies of slices of biopsy samples, sediment after centrifugation of urine and saliva, swabs from the bronchi.
All of these methods have different sensitivity and specificity (these are the special characteristics of the survey methods, determine the percentage of false positive and false negative results).
The table below grouped the information about the most popular of the above methods of diagnosis of cytomegalovirus infection.
|Name, the sensitivity (H) and specificity (C)||The percentage of undiagnosed cases of cytomegalovirus infection –false negative results||The percentage of positive reactions in the absence of CMV infection (false positive test)|
|RSK: H – 70-80%, WITH 70-80%||Up to 20%||Up to 20%|
|ELISA: W – 92%, 99-100%||To 5-8%||Not more than 1%|
|Immunoblotting: H – 98,3%; – 93,9%||1,7%||Not more than 1%|
|PCR: H, 99-100%, WITH 98-99%||Not more than 1%||Not more than 1.5%|
|Cytology: CH – 50% – 100%||Up to 50%||Not more than 1%|
In practice, the most commonly used second-fourth paragraphs.
Determination of levels of antibodies tocytomegalovirus
The level and presence of antibodies to cytomegalovirus in the practice of medicine often determined using ELISA and immunoblotting. For analysis of cytomegalovirus, venous blood should be taken on an empty stomach. Quantitatively, a positive result is considered when the titer of 1:100 (typically, but different labs may have different agents), a single definition of high titers of immunoglobulins IgG, IgM special diagnostic value has not. In addition to the credits, it is also important to determine the degree of avidity of antibodies of class G – i.e. the assessment of the density of binding of these immunoglobulins with antigens of cytomegalovirus. Different laboratories have different reference values of indicators of avidity. For example, "Invitro" gives the following values:
- To 0.3 – low avidity.
- Above 0.3 is high.
In other sources the value of the rate to 35% is considered low avidity, 36-41% of the average, more than 42% higher.
For the differential diagnosis of conditions caused by the presence in the body to cytomegalovirus, and survey carry out "the method of paired sera: blood sample is taken twice with an interval of 2-3 weeks, each time evaluated the titer and avidity. Diagnostically important criteria: the increase of titer in the dynamics by four times and increase the avidity index.
Transcript of the results obtained in the survey is presented in the table below.
|IgM||IgG||Which means the result|
|-||-||Uninfected people or in the incubation period|
|-||+, titer in the dynamics is not increasing, the high avidity||People in the past (long time ago) was infected|
|-||+, titer in the dynamics increases, the avidity any||People in the past (long time ago) was infected|
|+||-||The first week of the acute phase of primary CMV infection, repeat after 2-3 weeks perform PCR and other methods|
|+||+, titer in the dynamics is not increasing, the high avidity||Possible "tail of the IgM", after suffering more than 8-12 months. ago the CMV infection, or the activation of "dormant" in the body of the infection, or superinfection, redo the analysis in 2-3 weeks, to perform PCR|
|+||+, titer in the dynamics increases, the low avidity||The acute phase of primary CMV infection, to carry out PCR|
|For pregnant women the most dangerous options 4 and 6, since the risk of fetal infection is highest. Options 3 and 5 give the risk of infection fromfetus is about 2%. Option 1 shall be inspected every 3 months.|
Determination of DNA and separate antigens
To determine the presence of DNA in the starting material of cytomegalovirus using PCR or DNA hybridization, both methods are highly sensitive, in practice, often use PCR. To analyze the cytomegalovirus can be used any substrates, even when taken for a biopsy.
PCR is used only as a supplementary method of examination. This is due to its high sensitivity. However, up to 90% of the adult population of Russia are carriers of cytomegalovirus, which does not mean its activity in the body. Some authors doctors suggest to consider the detection of virus DNA in the serum and CSF of active CMV infection and the detection of genetic material in the urine, saliva, smears from the urethra and cervical canal/vagina is possible, and with latent (hidden) during infection.
Transcript of examination results by PCR and DNA hybridization in combination with the definition of the levels of specific immunoglobulins are given in the table below.
|Antibodies||CMV DNA by PCR and DNA hybridization||As evidenced by the results of the survey|
|No||Not found||The person is not infected with CMV|
|There are only vysokoavidnyh IgG||Not found||People have suffered CMV infection, now in the body of the virus no|
|Detected in urine, saliva, etc., there is no blood||A man who suffered CMV infection for a long time, in the body the virus is|
|There is, IgM, IgG nishaville||Found in blood/CSF||The man takes the active form of primary infection, to repeat the examination in 2-3 weeks|
|There is, IgM, IgG vysokoavidnyh||Found in blood/CSF||Activation of the infection up to this "sleeping" in the body, the second option superinfection, repeat examination in 2-3 weeks|
|For pregnant women the most dangerous option 3; option 1 shall be inspected every 3 months. For alternative 4 the probability of the fetus is 2-8%|
According to some sources, the main criterion of the activity of the CMVinfection should be considered as a detection of high titers of DNA-CMV in the blood of the examinee (1). Thus, in their opinion, the presence of increasing antibody titer 4 times and more), the detection of IgM, detection of virus DNA in blood and urine are not sufficient criteria for diagnosis.
Anyway, at the momentactivity for the diagnosis of CMV infection in the body use a combination of methods: definition of level of antibodies and detection of the virus and its antigens in various substrates.
Who should be tested for cytomegalovirus
Among the population, you can highlight categories of citizens requiring the most attention in relation to cytomegalovirus infection:
- pregnant women and women in period pregravidarnaya training;
- newborn babies;
- children with frequent viral respiratory infections;
- children and adults with immunodeficiency conditions, congenital or acquired, including HIV;
- children and adults with cancer;
- children and adults receiving cytotoxic agents;
- all citizens who have clinical manifestations of the infection.
- Problems of laboratory diagnosis of cytomegalovirus infection in HIV-infected patients. V. I. Shakhgildyan, Shipulina O. Yu., N. In. Free, Stakhanova V. M., L. F. Evseev, O. A. Tishkevich. The Russian Federal AIDS center PB, Moscow, Institute of epidemiology and Microbiology them. N. F. Gamalei RAMN, Institute of Virology D. I. ivanovskogo RAMN, Moscow Clinical infectious diseases hospital №2, Moscow.
- Congenital cytomegalovirus infection. The phantom menace. T. A. Artem, EE "Belarusian state medical University".
- Cytomegalovirus infection in the clinic of internal diseases. V. V. Skvortsov, R. G. Main, D. N. Emelyanov. The magazine "doctor", №9, 2004