Optimized detection of respiratory viruses in nasopharyngeal secretions

Nasopharyngeal secretions (NPS) from 121 (110 pediatric) patients with acute respiratory infections were examined for respiratory virus detection by: i) conventional virus isolation in cell cultures (CC) using HEp-2, LLC-MK2, and MDCK cells; ii) rapid virus isolation using shell vial cultures (SVC) of a mixture (MIX) of mink lung epithelial cells (Mv1Lu) and human lung carcinoma (A549) cells in comparison to LLC-MK2 and MDCK cells; iii) direct fluorescent antibody (DFA) assay on NPS cells. A pool of monoclonal antibodies (MAbs) to influenzavirus A and B, parainfluenzavirus types 1 to 3, adenoviruses and respiratory syncytial virus (RSV), as well as single MAbs to the same viruses, were used for virus identification in all three procedures. Results on 101 NPS examined in parallel showed a sensitivity of 89.5%, 73.7%, and 81.6% for CC, SVC, and DFA, respectively, with the relevant negative predictive values of 94.0%, 86.3%, and 90.0%. Specificity and positive predictive values were 100%. However, the combination of DFA and SVC gave best results in terms of sensitivity (94.7%) and negative predictive value (95.5%). Use of the new MIX cell culture system in the SVC procedure enhanced virus detection, while use of the MAb pool allowed prompt identification of negative samples and saving of reagents and time for all three procedures. The combination of DFA and SVC allows diagnosis of the large majority of viral respiratory infections within 48h, while conventional virus isolation on CC may be limited to laboratories involved in research and epidemiological studies.