Rapid antigen vs PCR: which COVID-19 test should you use?

Rapid antigen tests detect viral proteins directly and give a result in 15 minutes at home. PCR (polymerase chain reaction) amplifies viral RNA in a laboratory and can detect far smaller quantities of virus, typically reporting the next day.

Sensitivity: PCR remains the reference standard. Antigen sensitivity is highest during the period of peak viral load — roughly days 1 to 5 of symptoms — and falls away before symptoms start and late in the illness. Specificity for both formats is high, so a positive antigen result rarely needs confirmation.

Turnaround and cost: antigen testing costs less per test and produces an immediate, actionable answer. PCR costs more and adds a shipping and processing delay, but produces a laboratory-documented result.

Choose an antigen test when you are symptomatic and want a same-day answer, before a gathering, or for serial testing across several days. Choose PCR when you need documented evidence, when an antigen test is negative but symptoms persist, or when the result must be as sensitive as possible for a vulnerable contact.

Serial testing matters. Two antigen tests taken 24–48 hours apart substantially close the sensitivity gap with a single PCR, which is why multi-test packs are the recommended way to buy.