Calibration and Quality Control
- Created by: ellenrobinson
- Created on: 13-05-19 16:31
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- Calibration and Quality Control
- Methodology
- calibration concentration must be within range of assay
- Pure calibrants - SI units
- heterogenous analytes - IU/L
- concentration curve used to determine the concentration of unknown reactants
- multipoint calibration curve is read the same way as a straight line curve
- bumpy line - line of best fit
- Heterogenous analystes - mixtures of related molecules. different assays might have different fractions
- calibration concentration must be within range of assay
- Internal quality control
- detect, reduce and correct deficiencies
- types of assay errors: changes in bias & ageing or reagents,
- modern instruments - errors are rare
- IQC materials: known conc of analyte. should produce same value everyday
- stable, aqliquotes/ vials, covers normal and abnormal ranges
- new batches: run in new sampe. determine mean and SD, plot levey-jennings chart, rejection laws
- assessment : check results against correct value and look for tends
- Traceable systems of measurement
- Traceability is an unbroken chain of comparisons of measurement leading to a known reference value
- - Primary reference - primary calibrator - secondary reference methods
- Atomic absorption spectroscopy - quantitative determination of chemical elements using the absorption of optical radiation
- Thermal ioniszation mass spectrometry - highly sensitive isotope mass spectometry technique. Uses thermal ionization effect.
- Traceability is an unbroken chain of comparisons of measurement leading to a known reference value
- Practical Aspects
- Reasons to re-calibration
- validity of calibration
- Levey- Jennings Chart
- the distance from the mean is measured in SD
- A msrk is made indicating how far away the actual result is from the mean
- 1 3s - control rule (mean plus 3 above and below)
- 1 2s - waning rule (mean plus 2 aboe and below)
- R 4s - reject when 1 control measurement in a group exceeds the mean plus 2s and another exceeds 2 minus
- 10 x - reject when 1 control measurement in a group exceeds the mean +2 and another -2
- Point of care assay QC
- Format of assays
- Training of operators
- External Quality Assessment
- comparable results between labs
- Distribution of samples unknown composittion to different labs - collate results - find best method
- Lab Accreditation - in line with legislation and best practice
- inspection every 2-3 years
- Lab Accreditation - in line with legislation and best practice
- Total quality management : planning, improvement, lab practices, control & assurance
- Methodology
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