Method Evaluation and Quality Control
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Identify source of analytic variability: (1) experiments must be redone when blackout happens
power surges
Identify source of analytic variability: (2) temperature and humidity being kept constant as to why specimens and experiments are in a very controlled environment
environmental conditons
Identify source of analytic variability: (3) presence or absence of staining in 0.1 antibody may be caused by contaminated buffer solution
contamination
Identify source of analytic variability: (4) the medical technologist used the wrong speciment on the CBC test machine
operator technique
Identify source of analytic variability: (5) 3 Tesla MRI produces clearer image and abnormalities are detected faster than 0.3 Tesla MRI
Instrument differences
Identify source of analytic variability: (6) external features causing abnormal findings due to hemolysis, lipemia, serum proteins, specimen sitting too long or not properly centrifuged.
Matrix effects
Identify source of analytic variability: (7) two operators reading the EEG on different time scale in same instrument, one may look at it differently than the other.
Operator technique
Other sources of analytic variability:
Reagents Test accessories
An all-inclusive, comprehensive system monitoring the accuracy of test results where all steps before, during and after the testing process are considered which includes pre-analytic, analytic and post-analytic factors
Quality Assurance/Assessment
Essentials for quality assurance
Commitment to quality facilities, resources, competent staff reliable procedures, methods, instrumentation
Quality assurance provides what?
a structure for achieving lab and hospital quality goals
These systems monitor the analytical process, detects and minimize errors during analysis thus preventing reporting of erroneous test results
Quality Control
Quality control requires following published rules such as?
Westgard rules (accompanied by Levy-Jennings chart)
Type of QC done daily and serves as establishment of reference ranges and validation of new reagent lot and/or shipment. It is done following instrument repair
Internal
type of QC which involves proficiency testing wherein laboratory testing performances are determined via interlaboratory comparisons
external
It is integrated within routine workload and analyzed by personnel who are running the test. It is an ongoing evaluation of results to correct unacceptable results and assess employee competency
Proficiency testing
Pre-Analytical and Analytical causes of error
samples operators reagents (degradation, QC material degrad., calibrator d.) laboratory environment (atmospheric environment: dust, temp., humidity; utility e.: electircal, H20 quality, pressure) measuring system (instrument failure: software, optics drift, electronic instability)
Some post-analytical sources of error
incorrect reference values physician not notified of a panic or critical value incorrect interpretation of lab results by physician incorrect data entry of lab results
some errors involved in sample presentation and integrity
integrity: lipemia, hemolysis, interfering substances, clotting factors, incorrect tube presentation: bubbles and inadequate volume
some errors involved in operator capacity and staffing
capacity: training, competency (wrong use of machines +insufficient reagents) staffing: short staffing, correct staffing
A statistical analysis of lab test data helps define:
Reference ranges for patients Acceptable ranges for control specimens
statistical concept wherein all values are symmetrically distributed around the mean and has the characteristic bell-shaped curve. It is also assumed for all quality control statistics
Gaussian/Normal Distribution
What determines accuracy and precision in Gaussian distribution?
accuracy: mean of curve at center of curve precision: data is grouped together as represented by a well-rounded bell curve
What does a curve signify if its center is off the mean?
Low accuracy due to systematic error