Docfan Academy

Patients cannot see inside your analyser or your test kit. Quality control (QC) is how you prove, every day, that your test still gives the right answer.

What a control is

A control is a material with a known, expected result. You run it the same way as a patient sample. If the test gives the expected result, within the acceptable range, you have good reason to trust the patient results from the same run. The range comes from the kit insert or from your own laboratory's records. It is simply a target value with a safe margin around it.

Run controls as often as your SOP says, usually at the start of each day or run, and whenever something changes.

Calibration is not control

• Calibration sets the instrument to a known standard, using calibrators, so its readings line up with the true scale.
• Control checks afterwards that the system is still giving the right results.

Calibrate when the maker or your SOP says to. Then run controls. One does not replace the other.

When a control fails

1. Stop reporting patient results from that test.
2. Look for simple causes: expired or wrongly stored reagent or control, wrong control, pipetting error, dirty equipment, wrong settings.
3. Repeat with a fresh control. If it is still out of range, follow your SOP, which may include recalibration, a new reagent or a service call.
4. Check the patient results since the last good control, as your SOP directs.
5. Write down what you found and what you did.

Never keep re-running until a result happens to fall in range, and never adjust a result to make it fit.

Lot changes and records. When you open a new reagent or control lot, run controls before you report patients. Record date, lot, expiry, operator, result and action for every control.