Efficacy of Directigen® RSV testing in patient management following admission from a paediatric emergency department

Abstract

We investigated the use of the Directigen® Respiratory Syncytial Virus test performed under ‘Stat Laboratory’ conditions, in the management of infants after admission from the Paediatric Emergency Department (ED). The study group consisted of 242 consecutive paediatric ED patients tested by Directigen in the Stat laboratory during the winter 1995–1996 respiratory virus season. Specimens were submitted to the Virology Laboratory for confirmatory consensus testing utilizing in part, an in-house multiplex immunofluorescence assay (IFA) and conventional virus isolation methodologies. The sensitivity, specificity, positive and negative predictive values for Directigen, IFA, and isolation, were 71, 91, 85, 80%; 98, 100, 100, 99%; and 51, 100, 100, 72% respectively. Re-testing of 17 discordant original NP aspirates using Directigen, suggested that errors were due to technologist interpretation as well as to overt assay failure. The low analytical sensitivity and specificity of Directigen precludes its use in the clinical setting described in this study. Evening or weekend specimen collection, followed by IFA testing in a centralized Virology Laboratory at the start of the next working day, produces reliable test results. Among the small number of pediatric patients who might be candidates for antiviral therapy IFA testing should be made available on an on-call basis by Virology Laboratory.