The - flu season in the U.S. was the worst recorded since . There were an estimated 80,000 deaths and a record 900,000 hospitalizations for influenza and its complications. Rapid and accurate diagnosis of influenza can save lives by facilitating early treatment, save money by preventing inappropriate treatment, and prevent epidemics by minimizing viral transmission.
If you want to learn more, please visit our website Accu-Tell.
For accurate diagnosis, reverse transcription PCR (RT-PCR) is considered the gold standard. Rapid influenza diagnostic tests (RIDTs), although fast and convenient, often produce false-negative results. In fact, the WHO recommends that &#;in general, the use of RIDTs in hospitalized patients should not be encouraged where RT-PCR or immunofluorescence assays for influenza are available.&#;
And yet, both the CDC and the WHO include RIDTs in their repertoire of recommended diagnostic tools. This article explores the two very different tests and discusses when and why clinicians choose one or the other.
Ease of use and portability
RIDTs are simple-to-use dipsticks, cards, or cassettes that do not require laboratory conditions or extensive training&#;a huge benefit to isolated clinics with minimal staff and laboratory equipment. Their size makes them easily transportable and, when kept between 4?C and 30?C, RIDTs are viable for around 18 months.
RT-PCR, in contrast, must be performed by highly-trained staff using bulky, expensive equipment in dedicated laboratories. In the U.S., the tests must be performed at accredited clinical laboratories and in developing countries, clinics may need to send samples many miles to diagnostic centers.
Speed of diagnosis
The greatest benefit of the RIDTs is the short test time: less than 15 minutes, compared to one to eight hours for RT-PCR. RIDTs are point-of-care (POC) tests, so samples do not have to be sent to centralized laboratories; therefore, clinicians can start anti-viral treatment much sooner, which is vital for high-risk patients. The CDC recommends that clinics should not wait for laboratory confirmation of influenza before beginning antiviral treatment.
Specificity and sensitivity
RT-PCR is considered the most accurate method of diagnosis, with 90 to 100 percent sensitivity (the rate of true positive results) and specificity (the rate of true negative results) depending on the strain, patient age, and day of testing. The PCR method may have slightly reduced sensitivity after day three of infection in adults, but it performs better than other tests at this time. By using primers specific to RNA sequences, RT-PCR can confirm influenza as well as distinguish between strains and subtypes. Further analysis can identify a strain&#;s susceptibility to anti-viral agents, a useful resource during an epidemic. However, laboratorians must update primers regularly to keep up with antigenic shift and maintain test reliability.
RIDTs have a specificity of 90 to 95 percent, resulting in few false-positives. Their reported sensitivity varies from as low as 4.4 percent to 100 percent, and most often between 40 and 70 percent, so false-negatives are common, especially during peak influenza seasons. RIDTs display much higher sensitivity if used within the first three days of infection, or within seven days for children. Most kits can distinguish between influenza A and B but not subtypes within A or B: In , RIDTs could not distinguish pandemic H1N1 influenza A infection from the seasonal influenza A viruses.
Cost
RIDTs cost around $20 each, while RT-PCR tests are higher at $90, and real-time RT-PCR is significantly more. Transportation costs for isolated clinics increases the price of RT-PCR further. For many clinics in the developing world, RIDTs are the only affordable tests available.
In addition, a study of health insurance claims in the U.S. revealed that use of antiviral drugs dropped by almost 50 percent when RIDTs were used to diagnose influenza compared to no clinical test. The average cost of treatment when RIDTs were used was $62.46 compared to $192.83 after medical diagnosis without RIDTs. In , the total medical cost of influenza in the U.S. was an estimated $10.4 billion; clearly, further use of RIDTs could make a substantial impact on this expenditure.
Controversies and limitations
The high variance in RIDT sensitivity is a result of a myriad factors such as influenza type, viral titer, patient age-group, sample source, and experience and ability of the tester. Studies into RIDTs often vary in these factors, as well as in the RIDT kit used. It is very difficult, therefore, to assess the sensitivity accurately until more standardized studies are deployed.
Several new RIDTs have been developed with improved sensitivity. The BD Veritor system can detect much lower levels of influenza virus by employing an optical reader, with a sensitivity of 70 to 90 percent. The reader costs $300 and each cartridge is $16, adding a small amount to the cost of an individual test.
On the other hand, faster and more portable POC tests based on nucleic acid amplification technologies may someday provide clinic-based molecular testing comparable to RT-PCR. At around $50 per test, these POC tests are more expensive than RIDTs and require accurate and careful sample collection and expensive reading equipment. Sensitivities for these rapid molecular tests are more variable than traditional RT-PCR tests, so are not yet considered an adequate replacement.
Choice of test
Ultimately, the choice between the RIDT and RT-PCR methods is based on several factors. In an understaffed, ill-equipped clinic, or in the peak of an epidemic, RIDTs may be employed to confirm the influenza type for some of the patients presenting with influenza-like symptoms, but with the majority receiving treatment without confirmed testing. In such a situation, samples are collected for laboratory testing, using the RT-PCR gold standard to confirm infection type and subtype, for future reference and for use in epidemic recording and control.
In less manic times, RIDTs are a useful, inexpensive and rapid method of confirming influenza, and in some clinics they may be the only diagnostic tool available. When a negative RIDT result is obtained, clinicians must take other factors&#;such as exposure, risk of infection, severity of illness, and differential diagnosis&#;into account when deciding whether treatment or further testing is required.
Researchers have yet to confirm the benefits that newer tests can provide. If they are able to overcome the limitations of the current methods successfully, they will inevitably become the next must-have influenza diagnostic tools.
As the health care community prepares for flu season, one key challenge is determining whether patients have COVID-19 or seasonal influenza, given that both have similar symptoms. A laboratory test is needed to accurately diagnose either illness. This increased need for testing has the potential to tax a healthcare system that&#;s already severely resource-constrained.
What is the combined nasal test for flu and COVID-19?
A combined nasal test for the flu and for COVID-19 is a single swab test designed to look for both the flu virus and COVID-19 virus. Health care providers now have the option of providing a combined nasal test to detect the presence of COVID-19 and influenza A and B.
This multiplex test is performed the same as the COVID-19 swab test. Due to the similarity of flu and coronavirus symptoms, the multiplex test provides much needed rapid direction as to how to treat a patient&#;s medical needs.
Dual flu and COVID-19 tests have been approved
Fortunately, several multiplex tests that can detect both flu and COVID-19 have been issued emergency use authorizations by the FDA. The CDC Influenza SARS-CoV-2 Multiplex Assay is a real-time reverse-transcription polymerase chain reaction (RT-PCR) process that can detect and differentiate RNA from SARS-CoV-2, influenza A virus and influenza B virus in upper and lower respiratory specimens.
Several similar tests have also received FDA authorization, including Qiagen&#;s QIAstat-Dx, Roche&#;s cobas®, BioMerieux&#;s BioFire and a dual test from LabCorp that can also diagnose respiratory syncytial virus (RSV).
Flu test versus COVID 19 test
The biggest benefit of the multiplex test is that through rapid diagnosis there is no delay in providing appropriate treatment.
Common signs associated with both illnesses include fever, cough and fatigue. Patients with either virus may also report less-common symptoms such as muscle aches, gastrointestinal upset, congestion, sore throat, runny nose, loss of smell and headache.
While testing is the only way to rule in or rule out influenza virus or SARS-CoV-2, this study found that the order of symptom occurrence may provide insight into a potential diagnosis. Early indicators can help identify which patients to test quickly and provide useful guidance around taking precautions such as quarantining if COVID-19 is suspected. This is particularly important given that COVID-19 is two to three times more contagious than influenza.
Given the overlap in symptoms between influenza and COVID-19, this is critical. While symptoms can range in severity for both COVID-19 and flu, the overlap of symptoms can make it difficult to diagnose based on symptoms alone.
There&#;s a lot of overlap between flu symptoms and those associated with COVID-19. A study provides a few clues that may help with diagnosis. But the only way to know for certain is to test.
Researchers at the University of Southern California modeled and analyzed data from thousands of patients worldwide who were diagnosed with COVID-19, influenza, SARS (severe acute respiratory syndrome) and MERS (Middle Eastern respiratory syndrome). Their analysis showed that a cough is most likely the first symptom of the flu. In contrast, a fever is most often the first symptom of COVID-19 as well as SARS and MERS.
Symptom
Flu
COVID-19
Fever or chills
Yes; often lasts 3-4 days
Yes
Cough
Yes
Yes
Shortness of breath or difficulty breathing
Contact us to discuss your requirements of influenza swab technique. Our experienced sales team can help you identify the options that best suit your needs.
Yes
Yes
Fatigue
Yes
Yes
Sore throat
Sometimes
Yes
Runny or stuffy nose
Sometimes
Yes
Muscle pain or body aches
Yes; often severe
Yes
Headache
Yes
Yes
Vomiting and diarrhea
Sometimes; more common in children
Yes
Change in or loss of taste or smell
Sometimes
Frequent
Source: CDC
Another interesting observation was that the upper GI tract tended to be affected before the lower GI tract in COVID-19 cases; the inverse was true for MERS and SARS cases. A very small percentage of COVID-19 patients experienced diarrhea as an initial symptom. However, each of these patients went on to eventually have pneumonia or respiratory failure, which researchers hypothesize meant they had a more aggressive form of COVID-19. This could also be helpful information for clinicians to keep in mind, though more research is needed to support this theory.
And new variants of both COVID-19 and the flu may affect these symptoms,
What are the benefits of the dual COVID and flu test?
Normally two swabs would be needed to detect COVID-19 and influenza, one swab for each type of test. A multiplex test, however, such as the CDC Influenza SARS-Co-V (Flu SC2) Multiplex Assay can be done with one swab for the benefit of patients and healthcare professionals.
- A dual test is more comfortable for patients: Taking one sample is faster for patients and also means less discomfort. Worried patients can also get comprehensive results more quickly instead of waiting for two test results.
- A dual test drives faster diagnosis: When a medical professional can collect more information with a single test, they can more rapidly confirm diagnosis and make informed and targeted treatment decisions.
- A dual test frees up laboratory resources: When a single COVID and test can provide insight into multiple ailments, laboratories are able to conserve the use of reagents and other testing materials, while processing more tests in a given time period.
- A dual test helps control virus spread: Public health laboratories can use this dual test to collect data necessary for ongoing influenza surveillance while testing for COVID. Data from testing can help public health officials control the spread of both influenza and COVID-19.
What healthcare providers need to know for - season
Indicators point to a severe - flu season, making it important to prepare your office for a swell in influenza-like illness testing, in addition to the potential for COVID testing. The FDA notes that it remains possible for an individual to be infected simultaneously with influenza A virus, influenza B virus, and/or SARS-CoV-2, making it particularly critical to have dual tests on hand.
The CDC, in operation with other government agencies, makes recommendations for best use of existing vaccines and supports the development of new and better vaccines. Overall, the CDC is encouraging anyone over the age of 6 months to get their flu vaccination by the end of October , but acknowledges that vaccination at any time during the peak of flu season can provide critical protection. CDC also notes that it is acceptable to get a flu vaccine at the same time as a COVID-19 vaccine, although the organization encourages getting up to date on vaccinations without delay if one or the other is unavailable at a given time.
Puritan swabs can be used for combined flu and covid testing
As one of only two suppliers worldwide who produce the specialized swabs CDC recommends for nasopharyngeal sample collection, Puritan Medical has been at the epicenter of COVID-19 testing. Solutions like our HydraFlock and PurFlock sterile ultrafine flock swabs afford health care providers added certainty in diagnosing patients presenting with these common symptoms by providing better cell yield in the specimen compared to alternative solutions.
As COVID-19 testing in particular continues to evolve, Puritan continues to update its testing resources to connect healthcare providers with the best solutions for patient health and safety.
With the - flu season underway, combined flu and COVID-19 testing may prove critical in relieving some of the pressure and provide quick, accurate information to patients, practitioners and the community at large.
Looking for more? Check out these printable PDFs on how to collect a nasal and nasopharyngeal specimen.
Your success story starts here - Puritan Medical Products empowers you to transform concepts into reality. Launch your journey to excellence with personalized custom swab kits.
DISCLAIMER: The information on this site is not intended or implied to be a substitute for professional medical advice, diagnosis, or treatment. All content, including text, graphics, images, and information, contained on or available through this web site is for general information purposes only. Please consult with a licensed medical professional regarding the application of products.
If you want to learn more, please visit our website hiv1 2.
Comments
0