Systematic Approach
to QC Problems
Clément Arès
Sr Product Manager
Bio-Rad Laboratories (Canada)
Quality Systems Division
[email protected]
Manitoba Congress of Medical Laboratory Sciences
October 3rd, 2012
Agenda
• It’s out of Control!!!
• Collect Information
• Systematic Approach
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Determine type of error
Relate error to cause
Common factors
Relate to recent changes
Verify the solution and document
Assess effectiveness regularly
• Resources
MCMLS - October 2012
It’s Out of Control!!!
• Assess the magnitude of the problem
– Large or small variation are not treated the same
• Make sure patient results since the last “in
control” event can be retrieved if required
• Determine if other means of evaluating data
can provide information as to the acceptability
of the patient results
– Statistical Vs Clinical significance
– Fixed mean Vs Peer group mean
MCMLS - October 2012
Collect information
• Out of control situations can be caused
by :
– Instrument …
– Reagent …
– Calibration …
– Control (except if Bio-Rad!!!) …
…unacceptable performance
MCMLS - October 2012
Collect Information
• When was the last time the QC was acceptable?
• Did you introduce a new lot # of reagent?
– Keep track by adding a comment or an action in URT
• Did you introduce a new lot # of calibrator?
– Keep track using the group function in URT
• Was there a service call, maintenance or software
update done?
– Use the comment by instrument in URT to notify users
• Are all levels affected?
MCMLS - October 2012
Collect Information
• How do you compare to peer group?
– Check InstantQC database
• Did you run another control to confirm?
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Old Proficiency sample
Patient pool or patient from previous run
Old lot number of same control
Different lot number of same control
• Does the control perform the same on
multiple analyzers or reading cells?
MCMLS - October 2012
Collect Information
• Contact control manufacturer technical
support group to investigate if other labs
have reported an issue for this analyte
• Ask if there is a technical bulletin about
this issue
• Provide information collected (fax or email) to document issue and obtain help
for resolution
MCMLS - October 2012
Systematic Approach
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Determine type or error
Relate the type of error to possible causes
Consider factors common on multiple test
systems
Relate the problem to recent changes
Verify the solution and document the remedy
Assess effectiveness of the quality system on a
regular basis
MCMLS - October 2012
Determine the types of errors
– Random (sudden, unpredictable)
• 1-3S, R4-S
– Systematic (over time)
• 2-2S, 4-1S and 10-x
• Shift
• Trend
MCMLS - October 2012
Causes of Random Errors
– Random error are caused by:
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Bubbles in reagent and reagent lines
Inadequately mixed reagent
Unstable temperature and incubation
Unstable electrical supply
Individual operator error in pipetting, timing
etc…
• Defective unit-test devices – « flyers »
MCMLS - October 2012
Random error
– Much more difficult to find the cause
– Look at charts to see if trending or one time event
– 3 suggestions
• Inspect the instrument during operation
• Perform a precision run using 10 replicates of the same
patient sample and compare to IFU data
• Run sample in duplicate
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Causes of Systematic Errors
– Systematic errors are caused by:
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Change in reagent or calibrator lot
Wrong calibrator value
Improperly prepared reagents
Deterioration of reagents or calibrators
Change in sample or reagent volume due to pipettor
misadjustment or alignment
• Change in temperature of incubators and reaction block
• Deterioration of light source
• Change in procedure from one operator to the other
MCMLS - October 2012
Systematic error - Shift
– If sudden shift
• Inspect reagent, calibration, maintenance records
• Note recent actions
– if the shift occurred immediately following a
reagent replacement, verify that the lot number is
correct and has been checked out or calibrated,
and that the reagent has been prepared properly,
that the reagent is indeed the correct reagent.
MCMLS - October 2012
Systematic error - Trend
– Systematic trend
• Trends are caused by:
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Slowly deteriorating reagent
Calibration shift
Change in instrument temperature
Deterioration of a filter or lamp
• Review QC records before taking an action
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Common factors on
multitest systems
– Only one test involved
• Determine type of error and relate it to cause
– Several tests involved
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Do all tests have small or large sample sizes?
Do all tests use the same filter?
Do all tests use the same lamp?
Do all tests use the same mode of detection? (EIA, FPIA,
Rate, End-point)
• Do all tests have something in common: mechanical or
optical
MCMLS - October 2012
Relate the problem
to recent event
– When a problem arises, ask « What
changed? »
• Determine if the error is random or systematic
• Determine if the is a trend or shift
• Use systematic approach to isolate the cause
– Change only one thing at a time
– Document each action taken
MCMLS - October 2012
Verify and Document
– Retest the control to verify that the problem
has been resolved
– If QC is good, repeat patient samples from
out-of-control run
– Document the out-of-control event along
with the corrective action
MCMLS - October 2012
Assess effectiveness of your
quality system on a regular basis
– Use advanced software functions such a
« Total Error- Biological Variation » to do a
retrospective evaluation of your SPC rules
and determine:
• Frequency of statistical out-of-control events
• Frequency of QC values outside the TEa limits
during a period or across periods
• The amount of biais present, if any
MCMLS - October 2012
Assess effectiveness of your
quality system on a regular basis
– Are SPC rules too restrictive?
– Can you improve error detection with more stringent single
rule or complex multi-rule?
– Should the mean be adjusted?
– How much imprecision is there? Can it/Should it be
improved?
– How much bias is there? Can it/should it be improved?
– Is the consensus group appropriate to determine bias?
– Is the performance goal achievable or too lenient?
– How frequently is the test being recalibrated? Does it
exceed manufacturers recommendation?
MCMLS - October 2012
Resources
• www.youtube.com
– BIORADQC Channel
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www.qcnet.com/ca-en/QC_Education
www.westgard.com
URT 2.0 User Guide
Articles by Dr C. Parvin et al. in
Advance/Laboratory – Jan. 2011
MCMLS - October 2012
THANK YOU!
MCMLS - October 2012