Comparison of direct fluorescence assay and real-time rt-PCR as diagnostics for respiratory syncytial virus in young children

Abstract

Respiratory syncytial virus (RSV) is the major cause of lower respiratory tract infections in children worldwide. Early detection of RSV is critical to initiate proper care. Two methods, the direct fluorescence assay (DFA) and the real-time reverse-transcription polymerase chain reaction (rt-RT-PCR), that are used for RSV detection were compared. A total of 451 nasopharyngeal aspirates from children 5 years of age or less were tested for RSV using both methods. The overall prevalence rate of the RSV among the children was 23.7% with a significantly higher prevalence among children under the age of 6 months of age when compared to other age groups. The sensitivity of DFA in comparison to rt-RT-PCR was highest (86%) during the first 3 days of symptoms onset and decreased gradually till it reached 65% after the first week. The specificity of DFA in comparison to rt-RT-PCR ranged between 99 and 100% irrespective of the date of collection. We concluded that, although the rt-RT-PCR is more sensitive for RSV detection, the DFA offers a reliable point-of-care alternative detection method especially during the first few days of illness.

Figure 1

Age distribution of the RSV-positive patients. *Statistically significant difference (P < 0.05).

Figure 2

RSV-positive samples detected by each method at different times after onset of symptoms. SEN: sensitivity of DFA, SPEC: specificity of DFA, PPV: positive predictive value, and NPV: negative predictive value.