Module 6: Intro to Quality Control Flashcards
TQM
Total quality management
overall management of all quality processes and outcomes with the goal of long term customer satisfaction
QM
quality management
includes stages QS, QA, QC with a focus on financial impact of quality activities
QS
quality system
comprehensive and coordinated efforts to maintain and improve lab processes to meet quality goals
QA
quality assurance
planned and systematic activities to provide confidence that an organization fulfills quality requirement
QA monitors QC data and looks for opportunities to improve processes
QC
quality control
includes regular operational activities that ensure high quality test results
Intent of QC
identify and prevent issues
Statistical QC
monitors the performance of analytical methods by analyzing samples with known concentrations of analytes (ex. controls)
compare observed values with known values
Non Statistical QC
procedures to maintain and improve the performance of analytical systems
examples of nonstatistical QC
production and monitoring of high quality water for procedures
regular calibration of equipment, glassware, pipets, procedures
ensuring stability of power supply
monitoring temp of baths, fridge, freezer, centrifuge
performance and documentation of maintenance and troubleshooting
monitor prep and storage of reagents and standards
performance of linearity checks
Analytical system
procedure, reagents, calibrators, instrument
preventative maintenance
done to prevent development of problems
chemical buildup, corrosion, worn/damaged parts
calibration
process of analyzing known sampled of difference concentrations to make a curve
standard
material or solution of known concentration
3 types of error
pos (higher) or negative (lower)
random error
systemic
Error
difference between the true value and the measured value
accuracy
the nearness of a result to its true value
precision
the reproducibility of replicate measurements
Sensitivity
ability to measure low concentrations (minimal detection limit)
specificity
ability of an analytical system to accurately measure one analyte without interference from other substances
measures of central tendancy
mean, median, mode
mean
average of a set of values
median
the middle number in a set of data arranged in increasing numerical data
ex: 1,4,6,8,9
median = 6
mode
value that occurs most frequently in a data set
ex: 1,5,3,5,6,5
mode=5
SD or s
standard deviation
statistic that describes the dispersion or spread of a set of measurement about the mean of a Gaussian or normal distribution
Measurement of imprecision
Coefficient of Variation (%CV)
standard deviation expressed as a percentage of the mean
another way to describe precision of a method
No units, can be used to compare the precision of other methods
CV=(s/X)100
s=standard deviation
X=mean
the lower the %CV, the ______ the precision
better
Distribution
the spread and shape of a frequency curve
one type is the Gaussian curve
Gaussian distribution or curve (normal)
a symmetrical bell-shaped distribution whose shape is given by a specific equation in which the mean and standard deviation are variables
mean=median=mode at top of bell curve
non Gaussian distribution
a distribution that does not follow a bell-shaped curve
SD would not be a valid statistic
mean does not equal median does not equal mode
Control
known concentration
measured values are compared to a range of acceptable values
fall within range = assumed method is working properly
fall outside range = may indicate problem with the analytical system
control materials
ready to use liquid form or lyophilized/freeze-dried to be reconstituted with water or diluent
matrix similar to pt sample
single analyte control
control only contains one analyte at a known concentration
multi-analyte / multi-controls
contains a number of analytes at known concentration
Analytical run
interval in which performance/precision and accuracy of the measuring system can be expected to remain stable
a set time or a set # of samples
Run may never exceed 24 hrs and must contain both controls and pt samples
Control limits
defined limits or ranges of expected results that if exceeded, warn of an error in the system
obtaining control limits
each lab makes their own limits
mean and SD are calculated from data collected by running control sample under standard operating conditions (at least 1 month)
Minimum of 20 observations to establish a minimum estimate
+/- 1 SD
about 68% of values will fall within this range
+/- 2 SD
about 95% of values will fall within this range
+/- 3 SD
about 99% of values will fall within this range
Control chart
graphical method
plot control values to the expected results/ control limit
Levey-jennings chart
left y axis= control result
x axis= time (days or run #)
horizontal lines for the mean, +/- 1SD, +/- 2SD, +/- 3SD (written on right y axis)
chart should be big enough for +/- 4SD
Levey-jennings chart labeling (6)
name of the test name, level and lot# of control material units of measurement analytical system mean and SD time period covered by chart
if qc data is outside of +/-2 SD on levey Jennings chart
circle plot of graph in red and then trouble shoot (and document troubleshooting)
Troubleshooting (FIRED)
F: figure out what is going on (check for errors/flags, other controls ran on that instrument, recent maintenance, reagent and calibration logs)
I: Isolate the cause (RITE)
R: Resolve the issue (correct issues)
E: evaluate the resolution (repeating controls, if control is good, repeat all pt samples from failed run)
D: Document all steps and outcomes
Troubleshooting: Isolate the cause (RITE)
R: Reagents (new, expired, incorrectly prepared/stored, calibrators, diluents, washes)
I: instrument (dirty, damaged, new components, bubbles, leaks, precipitates, unstable temp or power supply)
T: technologist (error loading controls, operation, technique, fail to comply with maintenance/calibration schedule)
E: environment (room temp, humidity, power, fumes)
