Thursday, June 23, 2011

Cytomegalovirus infection in children - Diagnosis

Positive diagnosis:
Issuance of CMV positive diagnosis based on clinical correlation with laboratory data.CMV Isolation of human fibroblast cell culture is the method of choice. Harvest the blood, urine, tracheal secretions, lung aspirate transported, quickly transported to the laboratory and seeded with cultured human fibroblast cells.
CMV-induced cytopathic effect in cell cultures is achieved in 10-21 days limiting the use of this method. Despite these drawbacks virus isolation remains the reference technique, only it allows preservation strain isolated for further studies (to determine antiviral resistance and genetic analysis of the genome).
Ac obtain monoclonal revolutionized the diagnosis of CMV infection. Provides a more rapid method than culture, is obtained in less than five days by specific detection of a very early antigen (IEA) of CMV that can be detected by IF or immunohistochemistry using specific monoclonal Ac.This method is more sensitive than conventional viral culture, but not the viral strain preservation.
CMV infection can be detected in optical microscopy on histological or cytological samples of giant cells in newborns with cytomegalovirus urinele generalized in amniotic fluid in the broncho-alveolar lavage fluid in biposiile organ.
Antigenemia is a quantitative method is considered important because there is a correlation between the number of positive nuclei and the presence of clinical evidence.Research early or late antigens of CMV's can also be done in prelevatului cells (without prior culture) by IF or immunoassay methods, using monoclonal Ac.Examines the cells harvested: broncho-alveolar lavage, tracheal aspirates, amniotic fluid and biopsy fingerprints on the blade.The result is obtained within 3 hours. Isolation method is lower sensitivity and negative results can not rule out the diagnosis.
Determination of phosphoprotein pp 65 (major surface protein of the virus) in nuclei PMN (polymorphonuclear) is circulating a far superior method with a sensitivity comparable to culture or rapid circulating leukocytes (viremia). The exam is called "leukocyte antigenemia" of CMV's and has the advantage of being fast (5:00).The method is quantitative (by determining the percentage of PMN marked).It is considered that there is a direct relationship between clinical symptoms and antigenemia pp 65 and follow antigenemiei during anti-CMV therapy has prognostic value.
Diagnosis aims serum or indirectly in other pathological (CSF, aqueous humor) of anti-CMV antibodies. Although simple methods are considered, their contribution is limited by the randomness diagnosis of humoral response in immunosuppressed and passive intake frequency Action sanvine Following administration of products or organ transplants. Serological tests for diagnosis usually serve.Complement fixation and neutralization test confirmed the diagnosis in a 4 times increase in repetition titer response. CMV specific IgM Research in titre> 1 / 16 through IF is evidence for recent infection.
Currently used as serodiagnostic testing: automated ELISA tests to detect minimal amounts of Ac and detection of different classes of immune globulin and agglutination tests to detect fast-latex particles.The best test is the ELISA.
The absence of IgG in cord blood of newborns or exclude the infection. Their presence is of limited value, 50-80% of women of childbearing age have antibodies of IgG type to be transmitted transplacental antiCMV in newborns. A titre of IgG in newborn IgG titer greater than the mother can diagnose active infection (in practice the difference is difficult to interpret). A titer of IgG to decrease gradually to 1, 3, 6 months may exclude congenital infection. A titre of IgG suggests a persistent infection uncertain (but can not distinguish from the perinatal intrauterine infection).
This IgM at birth is suggestive of congenital CMV infection. For diagnosis of certainty is required and viral cultures. Negative IgM titre does not exclude congenital infection. Low IgM titer is suggestive of reactivated infection. IgM titre enough (30% of IgG) in the context of positive viral cultures demonstrate an active infection. ELISA for specific IgM antiCMV can give false positive results if the sample does not remove rheumatoid factor and IgG.
This antibody and antibody to CMV IgM and IgG specific make it possible to differentiate between primary and secondary infection with CMV.The rapid growth of IgM antibody with IgG titer slow sequential growth indicate a primary infection.Usually, antibodies will be detected 2-4 weeks after infection.Therefore, serological diagnosis is not useful in early detection of CMV infection.
Differential diagnosis:
During the newborn, the clinical picture manifested by microcephaly, intracranial calcification, hepatosplenomegaly with or without jaundice, altered liver tests, petechiae, eye abnormalities, bleeding is more common pathologic entities.
The differential diagnosis is with other congenital infections. One example is the TORCH syndrome comprising the triad: Toxoplasmosis, disseminated intracranial calcification characterized by diffuse over the entire brain and not according to traditional distribution, the periventricular CMV infection, Rubella, which is manifested by congenital heart and deafness in 100%cases, herpes simplex, which include skin lesions such as vesicles, keratoconjunctivitis, encephalitis nerve damage to the panel.
CMV infection is different from hepatitis B, varicella and syphilis, whose symptoms include: persistent rhinitis unilateral hepatoslpenomegalie, lymphadenopathy, anemia, chorioretinitis, ascites, meningitis, periostitis, osteochondritis, low birth weight, placenta great.

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