Week 1 Flashcards
What is quality management composed of:
Error detection - quality control
error prevention - quality assurance - audit
what is quality control
when you run QC you run a test in the same way you would a patient sample but you use known values
-helps detect issues with testing processes before results are released
-includes things like reagents, standards, water quality, temperature and pipettes, gram stain control slides, antisera to known cells, commercial hemoglobin control
-QC issues are important in identifying potential errors
what is accuracy and how is it measured
-close to true value
-correct values are obtained from standardized test materials, procedures and conditions
measure using comparison/test method vs reference method (what we got vs what we should have gotten)
-shown as a % error and inaccuracies are due to systemic error
% error = what is got - what I should get /what I should get x(100)
-error can be negative or positive which tells you the direction of the difference (bias) and is reported to 1 decimal place
what is bias
methods that regularly give results that are higher/lower than the reference
positively 3.0% or negatively -2.5%
what is precision
reproducibility - when multiple aliquots of same sample having a constant concentration repetitively. However, there will be a tolerance because you wont always get the same result
expressed as standard deviation (SD or s) or coefficient of variation (CV)
if the mean of two methods are the same use s
if the mean of two methods are different use CV
imprecision is random error
most important
what is descriptive statistics
foundation for monitoring performance (QC)
-basic data measures like shape, center - most common and spread - most impactful
for example when you measure glucose 100 times in a row there can be lots of results. But the results form patterns so you can assess predictability
how do you measure center
Mean - average, measure of central tendency, needs units and has the same decimal places as the data provided
Median- middle value after you arrange numbers in ascending order
Mode - most common number - rarely used as datas center but used to describe date that is bimodal
how to measure spread
-Standard deviation (s, SD) - precision
-describe how the data is distributed
-SD is married to mean so if if the mean changes so does the SD
-reported to one more decimal place than data provided
-units must be included always and use the same units as the data
-used for isolated set of data or to compare two data sets with equal means
Coefficient of variation -CV - for precision and scatter
-higher the CV- lower the precision (more scatter)
-lower the CV - better precision (less scatter)
-report to ONE decimal place
-used more often
-does not matter the values of mean- so can be used anytime
-Range - largest minus the smallest
how to measure shape
Gaussian distribution - symmetric distribution
68% of the data fall between ±1SD;
95% of the data fall between ±2SD;
99% of the data fall between ±3SD
what is random error
unpredictable
-no pattern
-change in s but not change in mean (precision is affected not accuracy)
what is scatter
-excessive variation with few coming close to the mean
-use s or CV
-points can be within +/- 2SD
-indicates precision issue and random error
-can be caused by instrument, operator, reagent or environmental issues
what is systemic error
- constant (difference between test and comparative value regardless of analyte concentration)
-proportional (when differences between test and comparative values are proportional to analyte concentration
-measurable
-affects results in the same direction
-give a change in mean but not s (accuracy is affected not precision)
what is trend
-gradual change over time that looks like a progressive problem - more than 6 values that are increasing or decreasing
-control chart indicate trends or warn of errors
-can be caused by faulty instrument -light source, accumulation of debris on electrode
-can be caused by change in control sample (gradual decrease in bilirubin when exposed to light)
-can be caused by change in calibrating standard (loss of constituents)
Indicates systemic error
what is shift
-change in ONE direct ; 4-6 values lying on one side of the mean
-loss of accuracy ; a sudden and consistent change
-can be caused by :
inaccurate sample volume
inaccurate standard
change in reagent or incorrectly prepared reagent
incorrect wavelenth setting on spec
change in light source
systemic error
what is an outlier
random error- does not affect mean or s if it is a large data set
-a value that is randomly too high or too low
-if it happens in the first few points there can be a precision issue
-usually human error- transcription error, improper wavelength setting
difference in what was expected vs what was delivered
a qc chart is done on?
-histogram which shows data distribution
-very common to see values past 1 SD
-4.5% chance to see values over 2SD - warning or false alarm because you can have ONE result outside of 2 SD but inside 3 SD
-however 0.3% probability to see a result outside of 3SD which can indicate problems with method or technique
what is a Levey Jennings Chart
-Chart uses mean, SD and CV
-results are put on the chart to see where they are in control or not. If the test is reliable. If not acceptable note - Results pending and withhold results
the chart must have:
-test name
-name of analytical system
-name and lot of control
-level - QC1, QC2
-measurement unit
-month and year
-mean and SD
The x axis is time
Y is the control values you get
the horizontal lines are the mean values
what is total quality management
-involves everyone to meet customer requirements and it must be managed
what are the parts of TQM
QP- Quality planning - eliminate problems that have been identified, make a standardized solution and monitoring its effects
QLP- lab processes that have been standardized - SOP
QC- Quality Control - monitor how well things are done through statistical methods, error detection, Westgard -quantitative (example of process control)
QA- Quality Assessment - also checks on how well things are done but prioritizes non statistical methods- , time to enter req, time to result, TAT. Outcome driven
QI- Quality Improvement -identifies problem and make solution goes back to QP
what are the quality system essentials
12 system essentials - building blocks for TQM
Organization
Personnel
Equipment
Purchasing and Inventory
Process Control
Information Management
Documents and Records
Occurrence Management
Process
Improvement Assessment
Facilities and Safety
Customer service
example of Occurrence Management or Organization
Risk Management - minimize chances of error , develop QCPs for specific risk
example of equipment -QSE
-must have method specificity so you can detect on component without another interfering
-high degree of specificity important
Purchasing and Inventory example
QC materials different than a standard .
Analyte of known concentration that is used to monitor the performance of a method not for calibration
-can be in house or commercial
what is the difference between lyophilized and liquid QC material
Lyophilized - must be reconstituted - can cause increased tech error, and can differ vial to vial
-cheaper
-reduced stability
-the material can stay in lyophilized state until the expiry date
liquid
-no reconstitution therefore no variability
-expensive
-increase stability - reduced waste however additives can increase matrix problems
what is the matrix
base material of QA material which includes all the additives
-same as sample being tested like whole blood, protein based for serum testing, water-based for urine tests, human vs bovine
what is the stability in QC materials
- longer stability reduces workload , reduces pulling out and testing new lots , best to buy a year worth of same lot
what is the vial to vial variability in QC materials
-you want minimum variability- good pipetting is key
-lyophilized vs liquid control
-reconstitution step must be standardized
what is assayed vs unassayed
-assayed control are those that have been tested by the manufacturer and include mean and ranges for each analyte . to be used as guidelines only
-allows you to chose materials that correspond with important levels
-even those the controls have been assayed you must QC them before you run
what is the analyte levels in QC materials
-need upper and lower limits so you must have 2-3 concentrations of each analyte
types of internal QC data controls
Individual - relate to other lab tests, delta checks, limit checks
group- test distribution stats, groups means, correlation study
what is a delta check
-checking current result against previous results
what is a limit check
-check if the result is physiologically compatible with life
what must a quality lab manual contain
-lab description
-policy statement
-definitions of the policies with supporting references
-validations
what is the role of IQMH
Accreditation
Proficiency Testing
Echocardiography Quality Improvement (EQI)
Education
PROFICIENCY TESTING
-mandatory proficiency testing of the pre-analytical, analytical and post-analytical performance of lab services to licensed medical labs in Ontario
-must test samples provided and submit as per guidelines to be compared with actual value.
-testing must occur through routine methods
what is dead volume
amount of sample that must be present to allow the primary probe to accurately pick up the sample aliquot in the AU480, if there is empty dead volume then sampling would be inaccurate
