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Flashcards in Method Evaluation and Quality Control Deck (45)
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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



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:

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



type of QC which involves proficiency testing wherein laboratory testing performances are determined via interlaboratory comparisons



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

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


What does a curve signify if it is spread out resulting in a flatter curve?

low precision due to random errors


What is an error?

difference between test and reference method results


type of error which is:
-present in all measurements
-can be either positive or negative
-can be a result of many factors including instrument, operator dependence, reagent and environmental variations
-an imprecision of the test system causing scattered control values around the mean

Random error


What are the causes of random error?

air bubbles in reagent
improperly mixed reagents
reagent lines, sampling, reagent syringes
improperly fitting pipette tips
clogged or imprecise pipettor
fluctuations in power supply


type of error which:
-influences observation consistently in one direction
-can be further broken down into constant and proportional
-displacement of mean from original value
-predictable and causes shifts or trends in contorl charts

systemic error


What are the causes of systemic error?

-change in reagent or calibrator lot numbers
-wrong calibrator values
-improperly prepared reagents
-deterioration of reagents or calibrators
-inappropriate storage of reagents or calibrators
-variation in sample or reagent volumes due to pipetter misalignments
-variation in temperature or reaction chambers
-deterioration of photometric light source
-variation in procedure between technologists