Detection of human metapneumovirus in paediatric nasopharyngeal aspirates by a TaqMan minor groove binder probe assay: a one-year prospective study in Belgium
Abstract number: p1656
Verstrepen W., Bruynseels P., De Smet A., Mertens A.
Human metapneumovirus (hMPV) has a relative high incidence in acute respiratory infections in children but is difficult to isolate in culture. The aim of the study was to decrease the number of undiagnosed viral respiratory infections in our hospital by means of a TaqMan minor groove binder (MGB) probe assay.
From October 2004 to September 2005 a total of 1387 nasopharyngeal aspirates from children presenting at our paediatric facility were analysed. RNA extracts from specimens negative for RSV, parainfluenzavirus and influenzavirus with an (in) direct immunofluorescence assay (IFA) were subjected to a TaqMan MGB probe assay in parallel with a previously published TaqMan assay.
Of the 1387 specimens, 371 (27%) were positive by IFA for either RSV (226), parainfluenzavirus (47), influenzavirus A (83) or influenzavirus B (15). HMPV was detected in 83 (8.4%) of the remaining 988 specimens subjected to the newly developed PCR. Of the patients with a positive hMPV assay, 46/52 (88.5%) presented with respiratory symptoms. 72% of the positive specimens were from children less than 2 year as compared to only 6% from children older than 5 years. Viral load was highest in children less than 1 year. A prominent seasonal variation was noted since more than half of the positive specimens occurred during the months March and April. There was no significant difference in the proportion nor viral load of positive specimens from ambulatory patients, patients admitted to a general ward or patients requiring intensive care. As compared to the published Taqman assay, diagnostic sensitivity and specificity were 97.6% and 99.9% respectively, whereas PPV and NPV were 98.8% and 99.8%. Method comparison (NCCLS guideline EP-9A) failed to demonstrate a significant difference between both assays when the threshold cycle (Ct) was between 22 and 41. Strongly positive specimens (Ct < 22) were associated with a lower Ct using the published TaqMan assay. However, the new TaqMan MGB probe assay appeared to be more sensitive for weakly positive specimens (Ct > 41).
The number of viral respiratory infections confirmed in our hospital was substantially increased by means of the hMPV TaqMan MGB probe assay. The new assay is a reliable alternative to the previously published TaqMan assay for detection of hMPV in nasopharyngeal aspirates.
|Session name:||XXIst ISTH Congress|
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