How to Read a Rapid Test Result
Direct answer: A valid result shows a control line; a test line means positive; no control line means invalid — repeat with a new device.
| Lines | Result |
|---|---|
| Control only | Negative |
| Control + Test | Positive (reactive) |
| No control line | Invalid — repeat with a new device |
Common errors
- Reading too late — a line appearing after the read window is invalid.
- Ignoring the control line — no control = invalid, regardless of test line.
- Treating faint line as negative — any visible test line within window = reactive.
Always follow the product IFU; a reactive result is presumptive and may need confirmation.
By Progene Bio Regulatory Affairs Team · Medical Device QA · Medical disclaimer · Last reviewed: 2026-09-12