Laboratory Diagnosis - Respiratory Syncytial Infections

Laboratory Diagnosis

◗ Specimens

These include respiratory secretions obtained by washing, suc-tioning, or swabbing of the nasopharynx.

◗ Direct antigen detection

The viral antigens in the nasal washings or nasopharyngeal aspirates can be detected by using ELISA or direct immunoflu-orescence antibody test using specific monoclonal antibodies.

◗ Isolation of the virus

The virus can be isolated from clinical specimens by inocula-tion of HeLa cells, Hep-2 cells, or monkey kidney cells. After 2–10 days of incubation, RSV is identified by the character-istic syncytium formation in the cells. Direct immunofluo-rescence can also be used to detect viral antigen in infected cells.

◗ Serodiagnosis

The ELISA is used for demonstration of antibodies in the serum. Demonstration of a fourfold or more increase in the antibody titer of acute and convalescent sera confirms the diagnosis of RSV infection.