R-Mix cells are faster, at least as sensitive and marginally more costly than conventional cell lines for the detection of respiratory viruses

Sensitivity of Respiratory Virus Culture When Screening with R-Mix Fresh Cells

“…However, they were able to identify respiratory viruses in 24 of these occurrences by alternative methods such as conventional cell culture, DFA testing, or immunoassays for influenza A virus and/or RSV. These specimens and the length of time required to perform supplemental tests were not included in their calculation of turnaround time (2). We also confirmed the presence of those respiratory viruses that were detected by the initial R-Mix stain but unidentified in the second vial with the supplemental cell lines incorporated into the protocol.…”

“…It was, therefore, necessary to prolong the duration of the culture (usually 1 to 2 days) until another cell type could be used for identification purposes. This type of occurrence was noted by Barenfanger et al who documented forty-six samples positive by the initial 24-h R-Mix screen from which a specific virus could not be identified by staining of the cells from the second R-Mix vial (2). They suspected that the virus was in such low titer that it went undetected in the cells from the second vial.…”

“…While the manufacturer recommends screening for respiratory viruses other than influenza virus after 48 to 72 h of incubation, we and others have modified this protocol to limit the number of necessary vials, shorten the time to detection, and maximize the recovery rate for influenza viruses (4,11). Unfortunately, a comparison to other studies cannot be made because, in those reports, no adenoviruses were identified in clinical specimens where staining at both 20 to 24 h and 40 to 48 h was employed (2,5). Regardless, we are currently investigating the need for further screening to enhance the rapid recovery and identification of adenoviruses.…”

“…Several studies have demonstrated the efficacy of R-Mix cells for the detection of several respiratory viruses from clinical specimens (2,5,7,11). This mixed cell line combines the greater sensitivity afforded by culture with a relatively rapid turnaround time for reporting of results compared to traditional tube or shell vial culture.…”

“…With serial dilutions of influenza A virus, R-Mix cells detected 4 to 5 log-fold fewer infectious particles than two commercially available immunoassays (11). In a prospective evaluation of culture for 396 respiratory specimens, 15 and 13 (both of 19) influenza A viruses were identified in R-Mix vials and cell culture, respectively (2). Other clinical studies have shown sensitivities (R-Mix versus cell culture) of 100% versus 67% and 100% versus 90% for detection of influenza viruses (5,11).…”