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[Evaluation of serum specific IgM detection in diagnosis of respiratory viral infections in children].

OBJECTIVE
The present study was designed to explore the practical application of the rapid etiological diagnosis by detecting specific IgM antibody against common respiratory viruses in children with acute lower respiratory infections (ALRI).


METHOD
Clinical specimens including nasopharyngeal aspirates and serum of acute phase from hospitalized children were collected from 207 infants and children with acute lower respiratory infections from March 2009 to September 2010. Seven common respiratory virus antigens were identified from the collected nasopharyngeal aspirates by direct immunofluorescence assay (DFA). ELISA was used to detect specific IgM antibody against RSV, ADV, IFVA, IFVB and PIV, while indirect immunofluorescence assay (IFA) was used to detect specific IgM antibody against RSV, ADV, IFVA, IFVB, PIV1, PIV2 and PIV3 in collected acute phase serum.


RESULT
The overall positive rates to detect viral antigen by using DFA, ELISA and IFA was 67.6%, 57.5% and 39.6%, respectively. The consistent rate of ELISA and IFA versus accepted DFA were 21.7% and 31.4%, respectively. The average days from onset of the symptoms to blood sample collection for those with the consistent results by ELISA and DFA were 12.0 d for ADV, 9.6 d for PIV2, 9.5 d for IFV, and 5.3 d for RSV, respectively, and by IFA and DFA were 15.0 d for PIV3, 9.2 d for ADV, and 7.4 d for RSV, respectively. Among all age groups, the consistent rate of serum viral IgM and antigen detections was highest in children younger than 3 years old.


CONCLUSION
Although there were differences between serum IgM antibody and viral antigen detections, specific IgM antibody detection was of value in early and rapid etiological diagnosis of pediatric ALRI, especially for young children. It could provide serologic evidence of respiratory virus infection. The diagnostic rate of pathogen could be improved if it was used in combination with viral antigen diagnostic methods.