D-2257. Viral Respiratory Infection in Older Adults: Utility of Direct Fluorescent Antibody Stain, Rapid Antigen Testing, Culture, and Multiplex Nucleic Acid Amplification
Session: Poster Session: Clinical Virology Laboratory Testing
Monday, October 27, 2008: 12:00 AM
Room: Hall C
Background: Diagnostic tests for viruses are increasingly used to diagnose respiratory tract infections (RTI). Although their testing characteristics have been defined in diverse adult and children populations, little data exist on the optimal diagnostic test for older adults. We seek to define the performance characteristics of 4 viral diagnostic tests in an older adult population. Methods: Nasopharyngeal (NP) swabs were obtained from patients with RTI or for surveillance at Durham VAMC from Feb 2007 - Apr 2008. DFA, R-mix culture with DFA at 24 hours (Diagnostic Hybrids), rapid antigen testing for RSV and influenza A/B (Binax NOW, Inverness Medical), and multiplex RT-PCR (xTAG RVP, Luminex Corp.) were performed. RVP was also performed on 20 NP swabs from children with RTI presenting at an outpatient clinic from Dec 2007 - Mar 2008. Mean fluorescence intensity (MFI), a semi-quantitative measure of analytes, was compared in positive adult and pediatric samples. Results: 295 adult specimens were obtained from 133 patients ≥ 49 yr of age. RVP yielded 5/213 positive results in surveillance samples, 16/67 in acute samples, and 3/15 in roommate samples (Table 1). Of the positives, average MFI (1940 U) was significantly less than that from 10 pediatric cases (3309 U) (p < 0.024).
Positive results from adult cases. Denominators indicate number of specimens with a positive result.
Multiplex PCRDFARapid Antigen24 hr Culture
Influenza B3/32/31/12/3
Parainfluenza 14/40/4NA0/4
Parainfluenza 32/21/2NA1/2
Conclusions: Our preliminary data suggest that older adult patients shed lower titers of viruses than children, necessitating a highly sensitive assay such as PCR to reliably detect respiratory viral pathogens.
Cathy Petti, MD1, Christopher Woods, MD, MPH, Christopher Polage, MD3, Edward Taggart, BS4, Lauren Caram, MD5, Rosemary She, MD1, Weston Hymas, BS4 and  R. C. She, None., (1)University of Utah School of Medicine, Salt Lake City, UT, (2)ARUP Laboratories, Inc, Salt Lake City, UT, (3)ARUP Laboratories, (4)Duke University Medical Center, Durham, NC