Swabbing for respiratory viral infections in older patients: a comparison of rayon and nylon flocked swabs

Hernes, S. S.; Quarsten, H.; Hagen, E.; Lyngroth, A. L.; Pripp, A. H.; Bjorvatn, B.; Bakke, P. S.

Nasopharyngeal swabs are easy to use after proper instruction, but swabbing for microbiological agents is often left with the least trained medical staff. In such cases, suboptimal swabbing may be relatively common. The sample collection in our study was performed by two experienced team members, thus, minimising the risk of suboptimal sampling. Whereas usually, considerable efforts are made to optimise the diagnostic procedures in the laboratory, less emphasis tends to be placed on the preceding procedures of sample collection. We believe that there is a lot to be gained from an increased awareness of proper sampling techniques and sampling tools. For semi-quantitative assessments of respiratory pathogens in children, immunofluorescent assays or viral culture have been widely applied [14, [17] [18] [19] , whereas in the current study, CT values were obtained for this purpose. Most studies applying real-time PCR for the detection of respiratory agents simply determine whether there is an infection or not. However, within each PCR experiment, there is a close relationship between the achieved CT value and the initial amount of specific nucleic acids in the sample. In this study, only samples taken at the same time from the same patient are compared and the CT values used for the calculations are collected from the same experiment. The calculations of differences in viral load relied upon the use of PCR assays with high amplification efficiencies. Factors other than the ones we have been examining are then minimised. In this manner, the method provides valid relative quantitative data when comparing distinct sample materials.