Laboratory Quality Control

Instrument calibration: vital first step for accurate results or just another clinical lab job?

Instrument calibration: vital first step for accurate results or just another clinical lab job?Effective instrument calibration should be viewed as the foundation of all laboratory patient testing.  It’s the first step to producing reliable patient results and assuring instrument performance.  This is the reason laboratories should be paying closer attention.

Calibration is used to establish a reference point that assists instruments to produce accurate results.  All instruments of measurement, whatever they measure, require calibration.  Even everyday items, such as kitchen scales for food preparation, require calibration.

The same principle applies to laboratory analysers but instead of using weights, labs run calibrators or ‘standards’ with a known concentration.  During calibration the lab programmes the instrument with the concentration of each analyte according to the information provided on the kit insert supplied with the calibrator.  The instrument then measures the calibrator and adjusts the reading to match the given values.

5 steps to choosing an appropriate calibrator

1. Use a third party calibrator, with independently assigned values, and which is not optimised to work with any specific instrument or reagent system.
2. Use a calibrator with the same matrix as a patient sample. (e.g. when calibrating urine chemistry tests ensure you choose a urine based calibrator)
3. Use a multi-analyte calibrator with a long shelf life, this will save your lab time and money.
4. Use a calibrator that is completely traceable to reference materials.  This ensures comparable and accurate test results.

It’s important to know when to recalibrate.  To ensure your instrument is establishing a reliable baseline and you are building a strong foundation for accurate patient results, frequent recalibration is recommended.

5 steps to successful laboratory calibration

1. Follow the instrument or reagent manufacturer’s instructions for calibration. If not available, choose a frequency that is dictated by your internal QC frequency.
2. Assess the required frequency of calibration when validating assays. Depending on the stability of the assay it may be necessary to recalibrate more/less frequently.
3. Re-calibrate every time a reagent batch is changed, unless you can demonstrate that changing reagent lot numbers does not adversely affect control values and patient results.
4. Re-calibrate when your QC results are showing a systematic bias – calibration can eliminate trends or small analytical bias.
5. Re-calibrate after major instrument maintenance, such as lamp changes, which can cause shifts in QC values.

By following these guidelines and using a calibrator from Randox, you can be assured your laboratory equipment is properly calibrated and the foundations for accurate patient results are in place.

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