title: Prospective comparison of R-mix shell vial system with direct antigen tests and conventional cell culture for respiratory virus detection.
abstract: OBJECTIVE
  Conventional cell culture (CC) has limited clinical utility as a result of the extended incubation period often required for virus isolation. Alternative methodologies have been introduced in an effort to improve turnaround times. One such system, the R-mix shell vial is discussed herein. The study objectives were: (a) to establish R-mix testing parameters as compared to direct antigen testing (DAT) and CC, and (b) to assess technical aspects and cost of R-mix in a high volume clinical virology laboratory.
  
  
  METHODS
  A prospective analysis of respiratory samples submitted to the clinical virology laboratory between November 2004 and April 2005 was performed. All specimens were inoculated onto R-mix shell vials (SV) and CC tubes; and a subset also underwent DAT for influenza A and B and/or RSV. A retrospective estimated cost analysis was made.
  
  
  RESULTS
  A total of 563 samples were included in the study, which collectively revealed a total of 207 viruses. Sensitivity of R-mix for seven major respiratory viruses ranged from 45% to 83% compared to CC and DAT, while mean time to detection (TTD) varied from 1.1 to 1.4 days. In addition to these viruses, 23 picornaviruses, 11 CMV isolates and 5 HSV isolates were detected by CC alone.
  
  
  CONCLUSIONS
  The R-mix system has similar sensitivity as CC for the detection of parainfluenza 1-3 and influenza A/B while dramatically reducing the TTD. Furthermore, it is significantly more sensitive and produces more timely results for RSV than CC; yet, neither method offers a diagnostic benefit over rapid DAT for RSV detection. The sensitivity of R-mix for adenovirus appears to be significantly lower than that of CC. Lastly, methodologies other than R-mix must remain in place under circumstances where identification of other potential viral respiratory pathogens, including herpesviruses and picornaviruses, is desired.
authors.affiliation: Clinical Microbiology Division, Department of Pathology, University of Texas Medical Branch, Galveston, TX, United States. prlasala@mdanderson.org
authors.forename: P Rocco
authors.initials: PR
authors.lastname: LaSala
authors.forename: Kimberly K
authors.initials: KK
authors.lastname: Bufton
authors.forename: Nahed
authors.initials: N
authors.lastname: Ismail
authors.forename: Michael B
authors.initials: MB
authors.lastname: Smith
mesh_terms: D000260:Adenoviruses, Human / Q000302:isolation & purification; D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D009980:Influenza A virus / Q000302:isolation & purification; D009981:Influenza B virus / Q000302:isolation & purification; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012136:Respiratory Syncytial Viruses / Q000302:isolation & purification; D012141:Respiratory Tract Infections / Q000821:virology*; D014776:Virus Cultivation / Q000379:methods*