The Role of Rapid Antigen Testing for Influenza in the Era of Molecular Diagnostics

Respiratory RNA Viruses

Acute upper and lower respiratory infections are a major public health problem and a leading cause of morbidity and mortality worldwide. At greatest risk are young children, the elderly, the chronically ill, and those with suppressed or compromised immune systems. Viruses are the predominant cause of respiratory tract illnesses and include RNA viruses such as respiratory syncytial virus, influenza virus, parainfluenza virus, metapneumovirus, rhinovirus, and coronavirus. Laboratory testing is required for a reliable diagnosis of viral respiratory infections, as a clinical diagnosis can be difficult since signs and symptoms are often overlapping and not specific for any one virus. Recent advances in technology have resulted in the development of newer diagnostic assays that offer great promise for rapid and accurate detection of respiratory viral infections. This chapter emphasizes the fundamental characteristics and clinical importance of the various RNA viruses that cause upper and lower respiratory tract diseases in the immunocompromised host. It highlights the laboratory methods that can be used to make a rapid and definitive diagnosis for the greatest impact on the care and management of ill patients, and the prevention and control of hospital-acquired infections and community outbreaks.

Viral Upper Respiratory Tract Infections

The upper respiratory system is one of the most common sites of infection for adults, but even more so for children. Several viruses, from variable families, cause upper respiratory infections which, although generally underestimated due to their typically self-limiting nature, underlie enormous healthcare resource utilization and financial burden. Such, otherwise “benign” infections, can have very significant sequelae both in the form of bringing about local complications but also inducing asthma attacks, thus greatly increasing morbidity. Their enormous prevalence also indicates that rigorous research should be undertaken in order to tackle them, in both the prevention and treatment field.

Influenza in the Emergency Department: Vaccination, Diagnosis, and Treatment: Clinical Practice Paper Approved by American Academy of Emergency Medicine Clinical Guidelines Committee

BACKGROUND

Influenza is an acute respiratory virus that results in significant worldwide morbidity and mortality each year. As emergency physicians, we are often the first to encounter patients with seasonal influenza. It is therefore critical that we draw on the most recent and relevant research when we make clinical decisions regarding the diagnosis, treatment, and prophylaxis of this disease.

METHODS

A MEDLINE literature search from August 2009 to August 2015 was performed using the keywords influenza vaccination efficacy AND systematic, influenza AND rapid antigen testing, and Oseltamivir AND systematic, while limiting the search to human studies written in the English language. General review articles and case reports were omitted. Each of the selected articles then underwent a structured review.

RESULTS

We identified 163 articles through our literature search, of which 68 were found to be relevant to our clinical questions. These studies then underwent a rigorous review from which recommendations were given.

CONCLUSIONS

Influenza vaccine efficacy continues to range between 40% and 80%. Vaccination has the potential to decrease disease severity and is recommended for individuals older than 6 months of age. If resources permit, vaccination can be offered to patients presenting to the emergency department. Rapid antigen detection for influenza is a simple bedside test with high specificity, but generally low sensitivity. If a patient presents with a syndrome consistent with influenza and has negative rapid antigen detection, they should either receive a confirmatory reverse transcriptase polymerase chain reaction or be treated as if they have influenza. Treatment with neuraminidase inhibitors can decrease the duration of influenza and is recommended in hospitalized patients, or in those with high risk of complications.

Xpert Flu for point-of-care diagnosis of human influenza in industrialized countries

Respiratory infections, particularly those caused by influenza viruses, represent the third-most important cause of death in the world due to infectious diseases. Nevertheless, despite the enormous publicity attracted by epidemics due to these viruses, laboratory diagnosis, documentation and recording of respiratory diseases is still unsatisfactory. Available diagnostic tests capable of providing results rapidly are either limited and insufficiently sensitive or highly sensitive and specific but insufficiently rapid. Considerable investment and research efforts have been made towards the development of new diagnostics for influenza A and B viruses and the Xpert(®) Flu assay (Cepheid(®), CA, USA) has emerged as one of the most promising. In this article, we review current knowledge of the Xpert Flu test, discuss its potential value as a point-of-care test and outline the potential leads for future development.

Evaluation and implementation of FilmArray version 1.7 for improved detection of adenovirus respiratory tract infection

The BioFire FilmArray respiratory panel is a multiplex PCR technology capable of detecting a number of bacteria and viruses that cause respiratory tract infection. The assay is technically simple to perform and provides rapid results, making it an appealing option for physicians and laboratorians. The initial product released by BioFire (version 1.6) was reported to have poor sensitivity for adenovirus detection and was therefore of concern when testing immunocompromised patients. This study evaluates the redesigned FilmArray assay (version 1.7) for detection of adenovirus. In this evaluation, we performed both retrospective and prospective verification studies, as well as a detailed serotype analysis. We found that version 1.7 demonstrated improved adenovirus sensitivity. In retrospective studies, sensitivity improved from 66.6% to 90.5%, and in prospective studies, it improved from 42.7% to 83.3%. In addition, when 39 clinically relevant serotypes were tested, 8 were not detected by version 1.6 and only 1 was not detected by version 1.7. The limit of detection remained the same when tested against serotype 4 but improved by 2 log units for serotype 7. Lastly, turnaround time analyses showed that the FilmArray assay was completed 3 h and 9 min after collection, which was more than a 37-h improvement over the previous multiplex PCR assay performed in our laboratory.