Performance of a nurse-led paediatric point of care service for respiratory syncytial virus testing in secondary care.

OBJECTIVES: To evaluate respiratory syncytial virus (RSV)-point-of-care-testing (POCT) performance among paediatric patients with respiratory symptoms, using the BinaxNOW(®) RSV assay performed by trained nurses on the paediatric ward, and compare results with those obtained by real-time polymerase chain reaction (PCR). METHODS: Four paediatric nurses were trained and certified in using RSV-POCT. Between October 2008 and March 2009, all hospitalised children below 5 years of age presenting with a suspected RSV infection had nasopharyngeal swabs (NPS) tested by RSV-POCT by the nurses and a real-time PCR targeting common respiratory viruses by laboratory staff. RESULTS: Among 159 NPS, 21 (13.2%) were RSV-POCT positive and 138 (86.8%) negative. All 21 RSV-POCT positive samples were positive by PCR, yielding a specificity of 100% (95% CI 95.7%, 100.0%). Of 138 RSV-POCT negative samples, 30 (21.7%) were RSV positive by PCR (sensitivity 41.2%; 95% CI: 27.9%, 55.8%). The positive and negative predictive values for RSV-POCT were 100% (95% CI 80.8%, 100.0%) and 78.3% (95% CI 70.3%, 84.6%) respectively. Other respiratory viruses were detected in 52/138 (39.9%) NPS. CONCLUSIONS: A POCT for RSV run by trained nurses can be used reliably as a first screening step in symptomatic children. Negative samples should be analysed for RSV and other respiratory pathogens by real-time PCR.

The prevalence of chromosomally integrated human herpesvirus 6 genomes in the blood of UK blood donors.

A lesser-recognized form of human herpesvirus 6 (HHV-6) persistence is integration of the viral genome in a host chromosome and high viral copy numbers in blood or sera are characteristic of this phenomenon. A cross-sectional study was performed to determine the frequency of high HHV-6 viral loads in whole blood (>6 log(10) copies/ml) in a population of blood donors in London, UK. Blood samples from 500 anonymized blood donors were collected from one donation center, DNA extracted, and quantitative realtime PCR used to measure viral load. Four samples (0.8%) were found to have high viral copy numbers of HHV-6 (median 6.7 log(10) copies/ml; range 6.5- 6.9 log(10) copies/ml). Cellular DNA was also quantitated using qRT-PCR for beta-globin. By comparing these two results, we calculated that there were between two and five copies of HHV-6 present per cell in these four donors. The median viral load detected in plasma from the four individuals was 3.8 log(10) copies/ml (range 3.5-4.0 log(10) copies/ml). All samples were HHV-6 variant B. In addition, a retrospective analysis of all diagnostic blood samples performed for HHV-6 in our center showed a prevalence of 2.9% of high viral loads characteristic of integration. In conclusion, high viral copy numbers of HHV-6, representing a population of viral integration, is detected in 0.8% of UK blood donors. The presence of high HHV-6 viral loads in healthy normal individuals reiterates the need to consider the confounding effect of HHV-6 viral integration in any laboratory diagnosis of HHV-6 infection.