What To Know About Flu Tests—When You Need One, and What To Do if You Test Positive

Plus, why it’s important to seek medical care as soon as you start experiencing

If you find yourself experiencing fatigue, a sore throat, a runny nose, and a fever in the autumn or winter season, the immediate assumption might lean toward a flu infection. Nonetheless, distinguishing with certainty between influenza and other ailments exhibiting comparable symptoms becomes crucial. Are there conclusive diagnostic measures available to confirm whether your symptoms indeed stem from the flu?

How Common Is the Flu?

Between 2010 and 2020, the Centers for Disease Control and Prevention (CDC) indicated that annual flu-related illnesses ranged from 9 million to 41 million cases—an approximation subject to variation.

The actual extent of flu cases remains somewhat elusive for the CDC due to various reasons. A significant factor is that numerous individuals with flu-like symptoms do not pursue medical attention, and even when they do, medical practitioners often omit flu tests as the treatment approach remains consistent irrespective of the diagnosis.

These complexities, coupled with instances where individuals seek medical care only after the window for flu detection has passed, contribute to the likelihood that the existing data potentially underestimates the genuine impact of flu within the United States during any given year.2

Employing a flu test stands as the principal method to ascertain whether an individual presenting flu-like symptoms is genuinely afflicted by the flu. The results from these tests play a pivotal role in enabling experts to gauge the severity of a particular flu season on the population.

However, the prospect of undergoing a flu test can be intimidating, given the nasal swabbing procedure involved. This guide aims to demystify flu tests, encompassing who typically necessitates such testing, the time frame for receiving results, and the recommended course of action following a positive influenza diagnosis.

How Do You Know if You Need a Flu Test?

The necessity for a flu test hinges on the symptoms you present to your healthcare provider and their diagnostic approach. The prevailing indicators of the flu encompass:

• Fever and chills (not universally present)
• Cough
• Sore throat
• Runny or congested nose
• Muscle or body discomfort
• Headache
• Fatigue
• Vomiting and diarrhea (typically more prevalent among children)

It’s noteworthy that these symptoms bear a resemblance to those associated with COVID-19. If your healthcare provider opts to conduct a COVID-19 test initially and it yields negative results, there’s a likelihood they will proceed with a flu test, according to Robert L. Murphy, MD, an infectious diseases professor at Northwestern University Feinberg School of Medicine.

Although the majority may not necessitate a flu test, certain circumstances warrant it, including:

• The individual possesses risk factors for severe flu complications
• Monitoring a local flu outbreak by the health department
• The affected individual has close interactions with individuals at a heightened risk of flu-related complications

Are There Different Types of Flu Tests?

Certainly, various categories of flu tests exist, each demanding either a nasal swab—where a healthcare professional gently swabs the interior of your nasal passages—or a throat swab, as explained by Cassandra Pierre, MD, MPH, an infectious disease expert at Boston Medical Center.

To delve into greater detail, certain tests require swabbing deeper into the nasal passages, whereas the rapid test is confined to a more superficial level inside the nose, as clarified by Anjali Mahoney, MD, MPH, a family medicine specialist affiliated with Keck Medicine of USC.

Rapid Tests

Various methods are employed to conduct influenza tests, with some available at healthcare providers’ offices or pharmacies. A prevalent diagnostic approach is the “rapid influenza diagnostic test” (RIDT), designed to identify specific antigens within the virus that trigger an immune response.

Another variety of flu tests is the “rapid molecular assay,” capable of detecting the genetic composition of the flu virus itself. Both of these assessments fall under the “rapid” category due to their ability to yield results within a brief timeframe—approximately 10 to 15 minutes for RIDTs and 15 to 20 minutes for rapid molecular assays.

Tests in Hospitals or Public Laboratories

Tests of higher accuracy compared to RIDTs and rapid molecular assays are commonly available in hospitals or public health laboratories, which possess more specialized facilities than typical urgent care centers or healthcare provider offices. These tests fall under categories such as reverse transcription polymerase chain reaction (RT-PCR) tests, viral cultures, or immunofluorescence assays. However, it’s important to note that these assessments entail a slightly longer waiting period for results, often taking several hours to be processed.

While achieving absolute accuracy is challenging for any test, Dr. Pierre underscores that flu tests exhibit a notable level of sensitivity and specificity. This implies that these tests are adept at indicating a positive outcome if an individual is indeed infected, while also providing a negative outcome if no infection is present. Sometimes, medical professionals may initially administer a rapid test to initiate prompt flu treatment, subsequently forwarding a sample for RT-PCR testing to ensure precise diagnosis. In all scenarios, the healthcare provider’s primary objective is to enhance the patient’s well-being and curtail community transmission. Dr. Murphy emphasized the significance of flu tests due to the availability of treatments tailored to flu infections.

Tests for COVID-19 and Flu

Equally significant is the existence of a test capable of screening for both seasonal flu and COVID-19. These dual-testing capabilities were dispatched to public health laboratories in August 2020, and the CDC has been consistently producing and disseminating these kits across the United States. (It’s noteworthy that co-occurrence of flu and COVID-19 is possible, underscoring the heightened importance of these dual tests.)

So What Should You Do After a Positive Flu Test?

Upon confirmation of a positive flu test, your healthcare provider will discuss available treatment choices. Additionally, the laboratory responsible for conducting the test will likely transmit the results to the respective state’s Department of Health. This practice aligns with the CDC’s strategy of gathering data on flu infections throughout the year in the United States.

Get Treatment

Your healthcare provider will also make a determination regarding the necessity for treatment. One of the treatments for influenza is the antiviral medication Tamiflu, also known as oseltamivir, which exhibits the capability to curtail symptom duration and mitigate severe repercussions. It’s crucial to note that its effectiveness is most pronounced within the initial 48 to 72 hours of symptom onset, as highlighted by Dr. Mahoney.

Further antiviral drugs such as Zanamivir, Peramivir, and Baloxavir can also be prescribed for flu treatment. The pivotal step is engaging with a healthcare professional as soon as symptoms manifest, as this timing is instrumental in optimizing treatment efficacy.

While Tamiflu and other antiviral medications are suitable for all individuals, healthcare providers frequently recommend it for those who:

• Are hospitalized
• Are significantly unwell but not requiring hospitalization
• Possess a higher vulnerability to severe flu-related complications or hospitalization (including pregnant individuals and adults aged 65 and above)

“Even if flu tests are negative, we might still consider treating these patients,” elucidated Dr. Mahoney.

In general, Dr. Pierre conveyed that patients typically tolerate Tamiflu well, though a subset of individuals may encounter side effects such as nausea, vomiting, diarrhea, and headaches.

Prevent the Spread

Apart from any prescribed antiviral medications or if you’re advised to manage your symptoms at home with adequate rest and hydration, it remains imperative to adopt preventative measures to avert transmitting the illness to others. The Centers for Disease Control and Prevention (CDC) offer the following recommendations:

1. Minimize close contact with others.

2. Regularly practice thorough handwashing.

3. Ensure cleanliness of frequently-touched surfaces.

4. Employ proper etiquette by covering your mouth and nose while coughing or sneezing.

Additionally, it’s prudent to remain at home as much as possible, with an exception for necessary medical care. A practical guideline is to wait for at least 24 hours post-fever resolution before resuming public activities. These precautions collectively contribute to safeguarding both your well-being and the well-being of those around you.