Respiratory tract infections are common and can be asymptomatic or manifest as a mild illness with progression to severe complications, hospitalization, or death. Influenza and other viral pathogens such as adenovirus, human metapneumovirus, respiratory syncytial virus, and rhinovirus are common. causes of respiratory infections. Early identification and diagnosis of the viral pathogen can allow the initiation of appropriate treatment and serve as confirmation of an outbreak to control and mitigate the spread of influenza.
Current diagnostic and surveillance approaches use the clinical presentation of the patient and a variety of diagnostic assays. However, this can present a challenge as overlapping symptoms render the clinical presentation of respiratory infections inappropriate for diagnosis. Laboratory diagnoses of respiratory infections have made enormous strides in recent years in providing results. timely and actionable during a patient encounter.
Laboratory diagnostic tests for respiratory tests have evolved rapidly in recent years. There are a large number of techniques and assays in the laboratory including traditional microbiological respiratory cultures, direct fluorescent antigen (DFA) tests, rapid serological assays, and pathogen-specific molecular assays. Each has a unique purpose and plays a vital role in the laboratory.
Several conventional test methods, including culture, DFA, and rapid tests, are subjective and depend on technique and user experience. Additionally, DFA is subject to photobleaching and proper digestion of lower respiratory tract samples. Another limitation of these conventional methods is response time. Many conventional methods can take several hours to days or weeks to complete. At the other end of the spectrum are rapid serology-based assays. Whether at the point of care or in the laboratory, these rapid assays allow rapid detection to see if a particular pathogen is present. Positives are generally confirmed by conventional microbiological methods. Rapid tests provide a quick screen but lack sensitivity compared to conventional microbiology.
Molecular tests, which typically provide a fast turnaround time, have become the contemporary method of laboratory diagnosis for respiratory viral infections. Most respiratory pathogen molecular test results are available in a couple of hours, and some platforms arrive in less than an hour. The first molecular assays were designed to target a single pathogen, but over time they have evolved into multiplexed panels that allow laboratories to analyze a single sample for multiple pathogens.
There is wide variation from manufacturer to manufacturer in chosen respiratory targets. Some all-encompassing panels test a large conglomerate of pathogens from a single sample, while other mini-panels test a handful of targets, and then there are tests for a single pathogen. However, this can be a double-edged sword. While results are available much faster, there is an additional cost for convenience. This may be counted toward the cost of the assay reagents and / or reimbursement for the tests based on clinical presentation and diagnosis.