COVID-19 + Flu A/B Combo Test — How to Distinguish Infections During Flu Season?

Why is a combo test better than a single test?

During the autumn and winter months, SARS-CoV-2, influenza A, and influenza B circulate simultaneously, creating a diagnostic challenge. The core symptoms of all three infections overlap substantially: fever, cough, sore throat, muscle aches, fatigue, and headache. It is clinically impossible to distinguish between COVID-19 and influenza based on symptoms alone — laboratory confirmation is essential.

The iLabU combo test (model ISIN-525H) solves this problem with a single nasal swab: two test cassettes on one platform detect SARS-CoV-2 antigens (nucleocapsid protein) alongside influenza A and influenza B antigens. Within 15 minutes you know which pathogen you are dealing with — or whether you have a co-infection, which does occur and can lead to more severe illness.

This approach saves time and money compared to purchasing separate tests. Instead of two kits and two swabs, one simple procedure gives you a comprehensive answer covering the three most common respiratory viruses in circulation.

How to perform the test step by step

The test uses a nasal swab from both nostrils. The entire procedure takes about two minutes:

1. Wash your hands thoroughly with soap for at least 20 seconds. 2. Remove the sterile swab from its sealed packaging. 3. Gently insert the swab approximately 2 cm into one nostril, then rotate it against the nasal wall 5–10 times. Repeat in the other nostril using the same swab. 4. Insert the swab into the buffer extraction tube, press it to the bottom, and rotate for 10–15 seconds to release collected material. 5. Remove the swab while squeezing the tube sides to extract maximum fluid, then cap the tube. 6. Dispense 3 drops into the sample well (S) of each test cassette. 7. Read results at exactly 15 minutes — do not interpret after 20 minutes.

Result interpretation: • COVID-19 cassette: C line + T line = SARS-CoV-2 positive • FLU cassette: C line + A line = influenza A positive; C line + B line = influenza B positive • Lines in both cassettes indicate a co-infection

COVID-19 vs flu — key clinical differences

Although symptoms overlap considerably, subtle differences can help guide expectations after a positive test:

COVID-19 is more commonly associated with: loss of smell and taste (anosmia/ageusia), shortness of breath, prolonged cough lasting weeks, "brain fog" and cognitive difficulty, and gastrointestinal symptoms (diarrhea, nausea). The incubation period ranges from 2 to 14 days, with an average of about 5 days.

Influenza tends to present with: abrupt onset of high fever (often exceeding 39°C/102°F), severe muscle and joint pain, intense headache, chills, and profound fatigue. The incubation period is shorter — typically 1 to 4 days, averaging 2 days.

Why does the distinction matter therapeutically? For COVID-19, isolation is necessary and antiviral treatment (Paxlovid) may be indicated for high-risk individuals. For influenza, oseltamivir (Tamiflu) is most effective when started within 48 hours of symptom onset. A negative result for both viruses with persisting symptoms may suggest a bacterial or other viral etiology — a medical consultation is warranted.

When to test and how to improve accuracy

The optimal time to perform an antigen test is 1–5 days after symptom onset, when the viral load is at its peak. Antigen test sensitivity is highest during this early symptomatic phase and declines after day 5–7 as the immune system begins clearing the virus.

To maximize the reliability of your result: • Perform the nasal swab thoroughly — complete the full 5–10 rotations in each nostril to collect an adequate sample. • If the result is negative but symptoms persist or worsen, repeat the test after 24–48 hours. A single negative antigen test does not definitively rule out infection. • Do not test too early — within the first 24 hours of exposure, antigen levels may be below the detection threshold.

The ISIN-525H test is CE 1434 marked for home use. Any shade of color on a test line, even very faint, should be interpreted as a positive result. When in doubt, consult a healthcare provider or consider a PCR test for confirmation.

Related product

• COVID-19 + Flu A/B Combo Test 20.00 PLN

Frequently asked questions

Does the test detect the latest SARS-CoV-2 variants?

Yes. The test targets the nucleocapsid protein (N protein), which is highly conserved across all SARS-CoV-2 variants, including Omicron and its sublineages. Unlike the spike protein (S), the N protein undergoes far fewer mutations, ensuring reliable detection regardless of the circulating variant.

Does a negative result mean I am not sick?

Not necessarily. Antigen tests are less sensitive than PCR tests, particularly when viral load is low (very early or late in the infection). If your test is negative but you have clear symptoms, repeat the test after 24–48 hours or consult a doctor about a confirmatory PCR test.

Can I test a child with this kit?

Yes. The test is suitable for all ages. For small children, an adult should perform the nasal swab, inserting it gently to a depth of 1.5–2 cm. Use slow, careful rotations and reassure the child throughout the process.