Methods: Results of the Simplexa ® Influenza/RSV Polymerase Chain Reaction (PCR) assay ordered for routine rapid diagnosis of viral infection in adults seen in the emergency room (ER) or admitted to Rochester General Hospital (Monroe County, NY) from October 2015- April 2016 were reviewed. Data were compared with rates of influenza like illness (ILI) ER visits and influenza activity in the county. Charts of adults testing positive for influenza or RSV were reviewed for discharge diagnoses (ICD-10).
Results: Of 3956 PCR assays 536 were positive; RSV 133 (30 ER, 103 hospitalized) and influenza 406 (216 ER, 188 hospitalized). Peak RSV activity preceded peak influenza activity by 10 weeks. Of hospitalized RSV cases, only 5 (5%) listed RSV as the primary discharge diagnosis, 51 (50%) in any discharge diagnosis while 52 (50.5%) failed to mention RSV. Notation of influenza in discharge diagnoses was significantly more common: 56 (30%) listed influenza as the primary diagnosis, 149 (79%) noted influenza in any discharge diagnosis and 39 (21%) had no mention of influenza (p<0.005 for all comparisons). To assess viral testing bias we calculated ratios of viral tests ordered to ER ILI activity in Monroe County during the 4 week periods of peak RSV and influenza activity. Notably, viral testing increased by 30% during peak influenza activity compared to the 4 weeks of peak RSV activity.
Conclusion: Our data suggest that routine viral testing to estimate RSV disease burden in adults may be useful but with limitations, especially testing bias. Mining ICD-10 databases for RSV related illness is problematic, even when RSV testing is positive, due to under reporting of RSV as a diagnosis on discharge forms.
A. R. Falsey, None
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