Objective Recently, real-time PCR has become available for quantitative respiratory syncytial virus (RSV) detection at the paediatric intensive care unit (PICU). Whether viral loads detected in the tracheal aspirates are in correspondence with loads from more conventionally used nasal aspirates needs to be determined.
Methods During the winter of 2007–8 ventilated infants at the PICU with an RSV bronchiolitis were enrolled. Throughout infection undiluted nasopharyngeal aspirates (NPA) and tracheal aspirates (TA) were taken simultaneously to determine RSV viral loads with real-time PCR. Viral load is expressed in Ct values; with low Ct values representing high viral loads.
Results Sixty-five NPA and 65 TA were tested. NPA and TA results set against each other showed considerable variation (figure). The mean Ct value in NPA was 3.9 lower than in TA (ie, the viral load was higher). Overall, NPA and TA showed less agreement near the lower limit of quantification (high Ct values). In samples taken at admission agreement was much better than in samples taken at discharge.