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- Biochemical Genetics Laboratory
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Biochemical Genetics Laboratory Viapath @Guys Hospital Marie - - PowerPoint PPT Presentation
Biochemical Genetics Laboratory Viapath @Guys Hospital Marie - - PowerPoint PPT Presentation
Biochemical Genetics Laboratory Viapath @Guys Hospital Marie Jackson Consultant Clinical Scientist
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interpretative comment. Uncertainty, variation and imprecision less significant? Example report:
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α α α-fucosidase the MU (95% CI) for an observed activity of 386 nmol/hr/ml would be 386 + 73
The MU for these enzymes has been calculated over a period of approximately 1 year from 29 assays. We can expect to take into account the variations expected in substrate lots, operator variability, reagent lot, pipettes, maintenance visits etc. Data is derived from IQC samples taken from the same donor at different times, which also takes into account some degree of biological variation.
Example of some MU values in plasma enzymes in our lab:
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- Clinical Significance of measurement uncertainty result:
The positive bias may result in a higher number of samples being tested for qualitative GAGs than would be the case with an assay of no statistical bias compared to the proficiency mean. However, this positive bias reduces the likelihood of missing the detection of a mucopolysaccharidosis and an elevated urine GAG result in isolation should not lead to an unnecessary clinical referral. In our laboratory qualitative (2-dimensional electrophoresis) is performed on all urine samples. ! #'
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Electrophoresis qualitative result Sample
Urine(pre-analytical – clinician/referral lab) pH (SOP, training, competency) Storage (Fridge/Freezer temp. monitored)
Reagents
Batch control (Batch number, Validation, Supplier – SOP, performance) Reagent stability (Fridge/freezer temp. monitored, standard samples)
Equipment & Environment
Pipette calibration (Biannual external) Electrophoresis tank (SOP) Powerpack (PAT tested) Lab temp. (Temperature monitoring) Centrifuge (Preventative maintenance, SOP) Balance (calibration, maintenance, SOP) Buffers (SOPs, training)
Cause and effect diagram identifying possible sources of uncertainty associated with Two Dimensional Electrophoresis of Glycosaminoglycans Extraction of GAGs Electrophoresis
Application of sample/
- standards. Pipetting precision
(training) Operator (Training/competency) Staining and visualisation
- f pattern (SOP, training)
Mixing (SOP, training Operator (Training/competency) Reagent mix (SOP, training) Pipette precision (training)
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- David Cregeen