Running a COVID-19 Antigen Test Kit Correctly: A Step-by-Step Procedure
Antigen rapid tests have become a common point-of-care and self-test format, and most results problems reported in the field trace back to procedure rather than to the test itself. For importers and distributors, a clear, correctly sequenced protocol is as important as the kit: it reduces invalid cassettes, avoids disputed readings, and gives your customers something concrete to place in instructions for use or training material.
The following is a full operating procedure for a SARS-CoV-2 antigen test kit, written for professional use and downstream training. All timings and conditions below refer to the standard format supplied by QL Biotek.
Step 1: Prepare the workspace and the kit
Before any sample is taken, three checks prevent most avoidable errors:
- Hygiene. Wash hands with running water or use hand sanitizer.
- Read the instructions. Confirm the procedure and the listed precautions against the insert supplied in the box — insert versions can differ between kit configurations.
- Check the kit. Verify that the components are present, undamaged and within the stated shelf life. Replace the kit if anything is missing, damaged or expired.
Environmental conditions matter more than most users expect. The test should be performed between 14 °C and 30 °C. Once the pouch is opened, use the test card within 30 minutes, and keep exposure to humid air (relative humidity ≥60%) short — prolonged exposure can affect the result.
Step 2: Collect the nasal sample
Sample collection is the step where user technique varies most, so it deserves careful wording in any training material.
- Blow the nose with tissue first.
- Open the swab wrapper carefully and avoid touching the swab head.
- Tilt the head slightly, hold the swab tail and insert it into one nostril along the floor of the lower nasal passage, 1–1.5 cm (for subjects aged 2–14 years, 1 cm).
- Rotate against the nasal wall at least 4 times, staying in place no less than 15 seconds.
- Repeat the same motion in the other nostril with the same swab.
Do not set the swab down between steps. Move directly to the extraction buffer.
Step 3: Extract and dispense
- Unscrew the cap of the swab treatment solution.
- Immediately place the swab head into the solution and rotate it for at least 30 seconds.
- While rotating, squeeze the swab head against the wall of the bottle at least 5 times to release as much liquid as possible from the swab.
- Break the swab at the fold line and leave the head inside the treatment bottle.
- Tighten the cap, then snap off the tip of the dropper cap.
- Remove the test card from the aluminium foil bag and place it on a flat surface.
- Invert the bottle vertically and dispense 3–5 drops into the sample well.
Vertical dispensing keeps drop volume consistent; tilting the bottle tends to overfill the well, which is a common cause of smeared or unreadable lines.
Step 4: Read the result at the right time
Interpret the card after 15–20 minutes of standing time. Results read before or after the window — in particular, later than 30 minutes — should be treated as unreliable.
| Outcome | Appearance | Interpretation |
|---|---|---|
| Positive | Purplish-red bands at both the detection line (T) and the control line (C) | A T line may be dark or light — any visible T line with a valid C line is positive. |
| Negative | Purplish-red band at the control line (C) only; no line at T | Control line confirms the test ran correctly. |
| Invalid | No purplish-red band at the control line (C), regardless of any T line | Repeat with a new kit; the test did not run correctly. |
The control line is the validity check, not a weak positive. Instruct users that any faint T line still counts as positive, and that a missing C line always requires a retest rather than a judgement call.
Step 5: Dispose of the used kit
Place every used component into the ziplock bag supplied with the kit, seal it, and dispose of it as medical waste or according to local waste-handling procedure. This keeps the buffer solution, used swab and cassette contained during transport to the disposal point.
Why the procedure belongs in your documentation
For distributors, this protocol is directly reusable: the timings (15–20 minutes reading, 30-minute maximum), the environmental range (14–30 °C, humidity limits), the sampling depth for adults versus children aged 2–14, and the invalid-result rule are the details end users ask about most. Reproducing them accurately in your product pages, inserts and support material reduces avoidable invalid tests and the returns that follow them.
FAQ
1. What happens if the result is read after 30 minutes?
A card read beyond the 30-minute maximum should be considered invalid. Lines can continue to develop over time, so a late reading may show a faint T line that does not reflect the actual test. Repeat the test with a new kit and follow the 15–20 minute reading window.
2. Why is my test invalid even though I followed the steps?
An invalid result means the control line (C) did not appear. The usual causes are too few or too many drops dispensed, the card being used outside the 14–30 °C range, exposure to humid air for too long after opening, or a card used more than 30 minutes after the pouch was opened. Check the environmental conditions and the drop count, then retest with a new kit.
3. Can the same procedure be used for children?
Yes, with one adjustment: for subjects aged 2–14 years, the swab is inserted to a depth of 1 cm rather than 1–1.5 cm. The rotation count, contact time, extraction steps and reading window remain the same as for adults.