RAPID CULTURE FOR INFLUENZA-VIRUS, TYPE-A AND TYPE-B, IN 96-WELL PLATES

Background: Rapid diagnosis and typing of influenza virus are important for patient treatment and management during seasonal outbreaks. Centrifugation-enhanced rapid culture has been reported to be useful as an adjunct to traditional tube culture for rapid diagnosis of influenza virus. Objectives: We compared rapid culture in 96-well plates against standard tube culture for recovery of influenza virus, types A and B. We also tested two different cell types, MDCK and RMK, to determine if the use of multiple cell lines increases the sensitivity of rapid culture. Study design: The rapid method was initially evaluated by retrospective culture of previously positive frozen specimens. It was then compared to standard culture for recovery of influenza virus by parallel testing of fresh respiratory specimens. Results: Of 32 previously positive frozen specimens, 28 were positive upon repeat culture. Rapid culture recovered 25 (89.3%) and standard culture recovered 23 (82.1%). All positives were type A. Of 722 fresh specimens cultured in parallel, 76 (10.5%) were positive for influenza virus: 43 for type A and 33 for type B. For type A, rapid culture recovered 42 of 43 (97.7%) and tube culture recovered 39 (90.7%). For type B, rapid culture recovered 33 of 33 (100%) and tube culture recovered 24 (72.7%). In the rapid system, the MDCK cell line was positive for 40 of 42 type A positives (95.2%) and the RMK was positive for 41 (97.6%). The MDCK line was positive for 32 of the 33 type B isolates (97.0%) and the RMK cells were positive for all 33 (100%). Conclusions: Rapid culture substantially seduced total test time and was more sensitive than tube culture. Duplicate cell lines did not significantly increase test sensitivity.