This study was conducted to assess the influence of a newly implemented combined flu/RSV test at the biggest tertiary care center in Austria. As expected, introduction of the test revealed that RSV is responsible for a substantial fraction of severe respiratory illnesses in adults during influenza season. Mortality in our cohort was high, and was even higher in patients with advanced age. Despite early and broad testing of our patients we were not able to safely discern any influence on admission rates to hospital or administration of antimicrobial agents.
When comparing RSV to influenza, overwhelming evidence showed similar rates of hospitalization, respiratory failure and mortality 7,12. RSV disease burden was particularly high in patients aged > 75years 6,14. Consistent with previous reports, our patients were mostly of advanced age and suffered from chronical diseases, such as oncological diseases, pulmonary diseases, diabetes mellitus type II and solid-organ transplant recipients. Previous reports have demonstrated rates of bacterial superinfections in up to 15% of RSV cases 7. In our cohort 11.1% of the patients suffered from superinfection. Most frequently reported pathogens were Streptococcus pneumoniae, Klebsiella pneumoniae, Enterococcus faecalis and Aspergillus fumigatus. Bacterial superinfections were associated with increased need for hospitalization and need for ICU admission.
Despite an increasing number of reports highlighting the disease burden of RSV in adults, awareness of many health care providers to adults seems to be low 12,13. RSV is known to be transmitted by aerosol droplets or direct contact to the virus, such as over contaminated hands or surfaces 15,16. During winter months RSV and influenza have their epidemic peaks in Austria, RSV usually a bit later than influenza virus. As a result, clinicians in emergency rooms and ambulances had to separate patients with respiratory tract infections due to RSV and influenza quickly and reliably to prevent nosocomial transmission. To tackle this problem, the general diagnostic procedure for RSV was revised in early 2018 by implementing a combined diagnostic assay for influenza A, influenza B and RSV. We demonstrate that a combined test led to an expected increase in performed tests and detected cases, but also to an increase in detection rate from 2.6 to 4.6%. The clinical presentation of patients with RSV and influenza is non-specific and similar, which makes it almost impossible to differentiate between the viruses based on symptoms alone. We believe that the demonstrated increase in detection rate emphasizes these diagnostic difficulties and supports the application of combined PCR tests in the clinical practice. At our center all positively tested patients were admitted to distinct wards and had to remain in quarantine for 5 days. Further, health care workers in contact with those patients had to wear personal protective equipment. Herewith we achieved a save and controlled handling of RSV patients.
Apart from the implemented measures, the impact of the test on the clinical reasoning is difficult to quantify. In theory, detection of viral pathogens responsible for pneumonia should reduce administration of antimicrobial treatment. Coinciding data from previously published retrospective studies showed that increased viral testing only partially altered antimicrobial treatment 17,18. Here, we demonstrate that reasoning for ab treatment depends on multiple factors such as an elevated CRP, clinical and radiological indication for pneumonia, as well as age of the patient rather than on the clinicians’ knowledge about RSV/test result.
Due to increasing availability and potency of viral diagnostic tools, viruses are increasingly detected as a cause for pneumonia world-wide. Clinical influence of broad viral testing was often discussed controversially, mostly due to three factors. Firstly, apart from neuraminidase inhibitors for influenza virus infections no specific antiviral options exists 19. Secondly, attempts to provide convincing evidence that broad antiviral testing reduces rates of antimicrobial treatment were unsuccessful 17,18. Thirdly, interpretation of naso-pharyngeal swabs poses a challenge of its own as the detected virus could be responsible for co-existing upper respiratory tract colonization or an actual pneumonia pathogen, making diagnosis difficult. 19. The above points should not be interpreted in the sense that testing is unnecessary, but rather that further research is urgently necessary to improve diagnostic procedures and the availability of treatment options. Currently, however, the biggest argument for broad-based testing remains the prevention of the spread of disease and protection of HCWs.
We acknowledge several limitations. First, our control group of patients with unknown RSV status was relatively small, as we only detected 10 additional cases. Hence, we only compared 10 patients from season 2018 to 103 cases in season 2019 in terms of clinical practice and reasoning, which is a limiting factor of our study. However, it is plausible clinicians’ select antimicrobial treatment based on multiple factors such as CRP, indication for pneumonia, age and not only on a test result. Furthermore, the assessed 191 samples corresponded to all samples during the suspected peak of RSV season in 2018, week 8 to 12. Hence, analysis of other periods would have been associated with increased efforts regrading costs and time. Secondly, we did not broadly test patients after the isolation period and cannot ultimately conclude if implemented strategies proved feasible in reducing risk of transmission after the isolation period. Finally, the present study was conducted retrospectively. Thus, the study design does not allow conclusions about the outcome of the patients besides the information documented in our system.
In conclusion, we demonstrated that although RSV disease is a well described cause for pneumonia in adults. Implementation of a combined influenza/RSV test led to a significant increase in detection rate, supported clinicians establishing the correct diagnosis and allowed a safe and controlled handling of RSV patients.