by Influenza, commonly known as the flu, is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs. The symptoms of flu include fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills and fatigue. While most people who get influenza will recover in a few days to less than two weeks, influenza can cause severe illness and life-threatening complications like pneumonia in some people. According to the World Health Organization (WHO), the seasonal flu causes about 3–5 million cases of severe illness globally and about 290,000 to 650,000 deaths per year.
With flu being so widespread globally every year, early diagnosis is important to help reduce the spread of the disease and save lives. Traditionally, confirmatory diagnosis of influenza has involved laboratory tests like viral culture, polymerase chain reaction (PCR) tests or immunofluorescent staining which take several hours to process. However, rapid diagnostic tests that can provide results within 30 minutes have become increasingly important for early diagnosis and management of influenza.
Rapid Influenza Diagnostic Tests
Rapid Influenza Diagnostic Tests (RIDTs) are medical devices that detect influenza viral nucleoprotein antigens in respiratory specimens such as nasal or throat swabs. They produce results much faster than traditional lab testing methods and do not require specialized equipment or highly trained personnel. RIDTs work on immunoassay principles using influenza virus-specific antibodies to detect viral proteins in specimens. If the viral protein is present, it will bind to the antibodies and generate a visually readable signal to indicate a positive result.
There are several types of RIDTs available globally that use different immunoassay formats like lateral flow immunochromatography, direct fluorescent antibody, and enzyme-linked immunosorbent assay (ELISA). Lateral flow tests are the most commonly used type that function similar to home pregnancy tests. The specimen is added to the sample well and flows along a membrane containing antibodies specific to viral proteins. A colored line develops at the test line region if influenza virus is present. These are simple to use and do not require specialized equipment, making them very attractive for point-of-care testing.
Clinical Applications Of Ridts
RIDTs enable early clinical decision-making at the point-of-care and are being widely used in primary care clinics, emergency departments, nursing homes and other healthcare settings globally. Their key applications include:
– Early Diagnosis: RIDTs allow clinicians to diagnose influenza within 30 minutes, enabling early treatment decisions without waiting for several hours for lab test results. This has been shown to improve clinical outcomes.
– Infection Control: Positive RIDT results help implement appropriate infection control measures like isolation and hygiene protocols earlier to contain the spread of the disease.
– Surveillance: Public health agencies use aggregated RIDT data to monitor regional influenza activity and trends to prepare for outbreaks.
Accuracy and Limitations of RIDTs
While RIDTs enable rapid diagnosis, their accuracy compared to viral culture or PCR is modest. A 2021 meta-analysis found pooled sensitivity of RIDTs to be 58% and specificity 98% compared to viral culture or PCR. Their lower sensitivity means they may produce false negative results especially when viral loads are low early in illness. Factors like specimen type and collection method can also impact test performance. False negative results may lead to missed or delayed diagnosis.
Additionally, RIDTs cannot differentiate between influenza A and B viruses. They are also unable to check for specific influenza strains which is important information for health authorities. Test interpretation can also be subjective and user-dependent. Standardized training of personnel is necessary to minimize errors. Overall, RIDTs provide presumptive rather than confirmatory diagnosis of influenza. Negative RIDT results require confirmation through PCR or viral culture testing.
Future Prospects
Rapid influenza tests are being continually improved upon by manufacturers to enhance their clinical utility. Newer multiplex tests can identify both influenza A and B viruses in one test. Development of self-contained, portable devices and smartphone-compatible tests hold promise to further expand point-of-care testing. Researchers are also working on developing rapid tests that can identify specific influenza strains rather than just type A or B.
Adoption of standardized electronic reporting of RIDT results will aid public health authorities for improved influenza surveillance. Use of RIDT data along with demographic details in digital frameworks can help monitor spread patterns and at-risk populations. Artificial intelligence and machine learning tools applied to aggregated RIDT data may uncover outbreak trends not evident from manual analysis.
With continued technological advancements, RIDTs are expected to play an even bigger role globally in managing influenza pandemics and seasonal outbreaks. Their easy, affordable, and rapid testing approach is invaluable especially in resource-limited areas to enable timely healthcare interventions and reduce disease spread. Though they have limitations, RIDTs will remain a mainstay for preliminary influenza diagnosis and point-of-care surveillance worldwide.
Overall, rapid influenza diagnostic tests provide a major advantage of enabling presumptive diagnosis and clinical decision-making within 30 minutes. Though their sensitivity is modest compared to lab tests, the early information they provide is invaluable for infection control, optimal patient management and public health surveillance of influenza globally. Continued improvements to these point-of-care tests will help maximize their clinical and epidemiological benefits in managing this significant viral respiratory disease. Rapid tests will be important tools in the ongoing effort to curb influenza mortality worldwide.
*Note:
- Source: CoherentMI, Public sources, Desk research
- We have leveraged AI tools to mine information and compile it
