Line T indicates a positive result. A positive result on a rapid antigen test shows two lines: one next to the "C" (control) and one next to the "T" (test). The presence of the line next to "T" confirms the presence of the target substance (in this case, often indicating a positive result for COVID-19). The "C" line is a control line, confirming the test is working correctly. Its presence is crucial, but it's the "T" line that indicates a positive test result.
Multiple sources confirm this interpretation:
- Multiple FDA-approved test instructions explicitly state that a visible line at "T", even if faint, alongside the "C" line indicates a positive result. These instructions emphasize that the presence of both lines is necessary for a valid positive test. [Example links: Pilot® COVID-19 At-Home Test instructions, OHC COVID-19 antigen self-test instructions](https://www.fda.gov/media/155126/download, https://www.fda.gov/media/157548/download)
- Numerous health organizations and medical websites corroborate this interpretation, emphasizing that both lines (C and T) are required for a valid positive result. [Examples: CBC News, Glenbio, Aurora Biomed, VSM Pharmacy, NHS England](https://www.cbc.ca/news/canada/new-brunswick/reading-rapid-antigen-test-kits-1.6227857, https://www.glenbio.com/covid-19-antibody/, https://www.aurorabiomed.com/interpret-results-covid-19-rapid-antigen-test/, https://vsmpharmacy.co.uk/what-does-c-and-t-mean-on-a-covid-test/, https://www.england.nhs.uk/coronavirus/documents/nhs-england-and-nhs-improvement-rollout-of-lateral-flow-devices-for-asymptomatic-staff-testing-for-sars-cov-2-phase-2-trusts/)
- The intensity of the T line may vary; even a faint line alongside a clear C line signifies a positive result. This is important to remember and is explicitly stated in several test instructions and interpretations.
