Monday, August 15, 2011

. Measles Laboratory Diagnosis

• Collection of samples, virus isolation and cell culture
Virus can be cultured from peripheral blood mononuclear cells, respiratory secretions, conjunctival swabs, and urine, but virus recovery is difficult and rarely used as the sole means of diagnosing acute disease. Cell lines vary in their susceptibility to infection by wild-type isolates, with primary monkey kidney cells, human cord blood leukocytes, and B-cell line being most sensitive (Smaron et al., 1991).
• Serology
The clinical diagnosis of measles is most often confirmed by serology. Samples ideally consist of acute and convalescent serum pairs, but detection of IgM in serum or saliva or low avidity IgG in serum is diagnostic and may require only a single sample (Fick de Souza et al., 1997). IgM antibody appears at the time of the rash and can be detected by 3 days and up to 4 weeks after the onset of the rash in most individuals (Helfand et al., 1997). IgG peaks approximately 2 weeks after the onset of rash and gradually increases. EIA allows differential detection of IgM and IgG and is widely used because of its convenience (Bouche et al., 1998).
• Molecular detection
Direct detection of virus RNA by RT-PCR is of particular importance for diagnosis in immunocompromised individuals in whom Ab responses may not be present (Jin et al., 1996).

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