For hematology analyzers, the calibration process is performed at the time of installation and as per the manufacturer's recommendations and minimally every six months as per compliance requirements. Measured parameters are evaluated in the calibration process. White blood cell differentials are not calibrated in the calibration process. Required adjustments for white blood cell differentials must be made by representatives of the manufacturer.
Additional conditions when the analyzer should be calibrated include:
- Following major preventative instrument maintenance or replacement of critical operating parts.
- Quality control material with an unexplainable trend or outside of acceptable limits which cannot be corrected by maintenance procedures or troubleshooting the instrument.
- Upon the advice of technical support or service representatives.
Calibration can be accomplished by using whole blood samples that have been assayed by reference methods or a calibrator material assayed with system-specific values traceable to a reference method. When assaying the calibrator material, replicate analyses are performed on individual whole blood calibrated hematology analyzers.*
Precision evaluation is incorporated into the calibration process and must be completed with successful results before performing calibration. A fresh, normal patient sample or a fresh vial of a commercial product that reflects normal patient values is evaluated. The sample is tested on the instrument 11 times. The first run is eliminated. The mean, standard deviation (SD), and coefficient of variation (CV%) are calculated, and the results are compared to the limits in the performance specifications for the analyzer. If any parameter's CV% exceeds the limits, perform troubleshooting and repeat the precision check.
The calibration procedure is performed following the manufacturer's instructions. Following an appropriate number of test runs, the mean is calculated. Compare the calculated mean to the assay target. If the results are within the assayed tolerance limits, no change in instrument settings is required. Accept the new calibration factors if the obtained calculations are close to the tolerance limits. This process and adjusting the calibration factors tell the analyzer how to read the analyte concentrations.
Following completion of the calibration process, evaluate quality control. Verify acceptable results. If post-calibration quality control is not acceptable, perform troubleshooting and repeat calibration if necessary.
Calibration verification is performed each day of testing. Successful testing of at least two levels of quality control serves as verification of calibration for automated cell counters. Achieving results within range for the quality control material verifies calibration.
* "General Hematology Calibration Procedure Guideline." Streck.
