3-in-1 COVID-19 and Flu A&B combo tests explained

COVID-19, influenza A and influenza B produce overlapping symptoms — fever, sore throat, cough, aches and fatigue — which makes them difficult to distinguish clinically. A 3-in-1 combination antigen test screens for all three pathogens from a single nasal swab.

Inside the cassette are separate lateral-flow strips, each coated with antibodies specific to one target: SARS-CoV-2 nucleocapsid antigen, influenza A nucleoprotein and influenza B nucleoprotein. One sample is distributed across all three, so you read up to three independent test lines beside a shared control line.

Widely used examples of this format include the iHealth COVID-19/Flu A&B Antigen Rapid Home Test, the BinaxNOW COVID-19/Flu A&B Card and the Equate COVID-19 & Flu A/B Test. Remedium's combo kits use the same 3-in-1 lateral-flow principle and the same shallow anterior-nares sampling.

When a combo test is worth it: during winter and travel seasons, when household members are symptomatic, before visiting elderly or immunocompromised relatives, and whenever a positive influenza result would change treatment — antivirals such as oseltamivir are most effective within 48 hours of symptom onset.

Limitations: antigen tests are less sensitive than PCR for all three targets, particularly in the first 24 hours of symptoms and in asymptomatic screening. A negative combo result in a symptomatic person should be repeated after 24–48 hours or followed by a laboratory PCR assay.

Practical note: one swab, one 15-minute wait and one disposal step makes combo testing considerably faster than running separate COVID and influenza kits, which is why it has become the default choice for households and offices.