BACKGROUND: We have recently initiated a randomized control trial to assess whether rapid influenza detection test (RIDT) availability in long term care facilities (LTCFs) is associated with earlier detection of influenza and reduction in influenza-related hospitalization and death. The effectiveness of this trial is predicated on knowing the ability of RIDTs to detect influenza in LTCF populations.
METHODS: To assess the performance characteristics of the Quidel Sofia Fluorescent Immunoassay Analyzer for Influenza A+B and RSV, we set up an acute respiratory illness surveillance network in 7 LTCFs across southern Wisconsin. One site was a large facility for persons with severe developmental disability and had younger patients than most LTCFs. Nasal specimens were collected, using foam nasal swabs, from residents with acute onset (<4 days) of at least two of the following symptoms: fever, cough, sore throat, nasal congestion, runny nose. Specimens were collected from December 2015 through December 2016 and tested for influenza and RSV using Quidel Sofia FIA. Influenza RT-PCR and a multiplex PCR respiratory pathogen panel (RPP) were also performed.
RESULTS: Of the samples tested by PCR (N=60), 39 (65%) were positive for a respiratory virus. Eight different respiratory viruses were identified in the LTCF population: rhino/enterovirus (38%), RSV A (21%), influenza A (13%), coronavirus OC43 (8%), parainfluenza 1 (8%), parainfluenza 4 (5%) coronavirus NL63 (5%), and human metapneumovirus (5%). 58 paired samples were available for influenza assessment and 24 paired samples were available for RSV assessment. For influenza, the mean age (±std. dev.) was 56.9±19.8 years; median = 50 years; range [24-93 years]. The sensitivity and specificity for Sofia influenza A+B FIA were 60.0% [95% CI: 14.7-94.7] and 94.3% [84.3-98.8], respectively. For RSV, the mean age (±std. dev.) was 44.09±6.9 years; median = 45 years; range [30-55 years]. The sensitivity and specificity of Sofia FIA for RSV were 60.0% [14.7-94.7] and 94.7% [74.0-99.9], respectively.
CONCLUSIONS: Many respiratory viruses circulate within LTCF populations. Influenza and RSV—in this study—accounted for 44% of illness episodes. Together, these findings indicate that Quidel Sofia Fluorescent Immunoassay Analyzer for Influenza A+B and RSV may be an effective tool for early detection of influenza and RSV in LTCFs. Although the sensitivity is moderate at ~60%, the likelihood of picking up one of the first three cases of influenza within an institution is estimated at 93.6%. Accordingly, aggressive use of Rapid technology may allow for early outbreak detection and response.