A comparison between real-time quantitative fluorescence polymerase chain reaction assay and direct immunofluorescence assay for diagnosis of human metapneumovirus

Objectives To evaluate the diagnostic value of real-time quantitative fluorescence polymerase chain reaction( Q-RT-PCR ) assay and immunofluorescence assay for diagnosis of hMPV. Methods Totally 1 283 children with acute respiratory infection admitted in Jiaxing Maternity and Child Health Care Hospital for treatment from November 2008 to May 2009 were recruited in this study. The hMPV positive stains were separated and sequenced in this area. The sequences between the local hMPV stains and Holland stains NLD00-1 were compared. The specific primers and fluorescent probe were designed according to the sequence of epidemic hMPV strain. The Taqman methodology was applied in Q-RT-PCR. Negative pressure suction was used to acquire nasopharyngeal secretions specimens. Both Q-RT-PCR and immunofluorescence with FITC labeled monoclonal antibody were used to analyze them, respectively. The McNemar, test was applied to analyze the correlation between the two methods. Results Totally 1 283 specimens were analyzed with Q-RT-PCR and immunofiuorescence simultaneously. Q-RT-PCR analysis showed there were 59 cases positive. Immunofluorescence analysis showed there were 55 cases positive. Fifty-two cases were positive in both assays. There were 7 cases positive in Q-RT-PCR assay but negative in immunofluorescence assay and 3 cases negative in Q-RT-PCR assay but positive in immunofluorescence assay. If Q-RT-PCR method was set as the golden standard, the sensitivity and specificity for immunofluorescence detection method were 88. 1%and 99. 8%, respectively. Positive predictive value and negative predictive value were 94. 5% and 99. 4%,respectively. There was no significant difference ( χ2= 0. 9, P ＞ 0. 05 ) by McNemar' test between the two methods. Conclusion The diagnostic value of immunofluorescence assay is close to Q-RT-PCR assay. Key words: Metapneumovirus; Fluorescent antibody technique,direct; Reverse transcriptase polymerase chain reaction