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MSC: Analytical Methods > EQA and IQC > Flashcards

EQA and IQC Flashcards

1
Q

Why is quality important?

A
  • Best patient outcome
  • Best patient experience
  • Safe practice
  • Need confidence in results produced
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2
Q

What is Internal Quality Control?

A

Used in real time to monitor the performance of an assay.

  • IQC is on the day so to check if we have the same result with different samples
  • IQC – if we put this same sample through repeatedly would we get the same answer and is it close to the expected value?
  • Checks reproducibility and accuracy of results ght material – is an assay producing the correct results for a patient sample?
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3
Q

What is External Quality Assurance?

A

Retrospective analysis of performance of an assay in comparison to other users

  • Do you produce the same results for the same sample as other labs with the same analyer?
  • Do different platforms perform the same?
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4
Q

What is the impact of IQC and EQA?

A
  • Ensure patient analysed in the same lab will receive continuity of results and therefore clinical care
  • Patients analysed in different labs should have equivalent results
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5
Q

What is IQC/EQA material?

A

IQC

  • Generally bought commercially
  • Can contain one or multiple analytes
  • Analytical results monitored by using a computer programme

EQA

  • Obtained by signing up to an EQA scheme
  • All assays should be subject to EQA
  • If not sample exchange scheme
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6
Q

What are the factors considered when choosing IQC material?

A

Matrix

  • Close matrix match
  • Human preferable, but not always possible

Third party

  • At least one QC used should not be made by the assay manufacturer

Cost

  • Most cost effective without compromising on quality

Levels available

  • Minimum of 2 – normal (physiological) and high (pathological)
  • Near cut off value

Range of analytes

  • Able to QC multiple assays The different QCs you select need to cover your whole assay range

Stability

  • Use repeatedly
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7
Q

How often do you need IQC?

A

Depends on frequency of analysis

  • Batch analysis requires IQC at least at the beginning and end. If large number of samples also benefit from IQC in the middle of a batch as well
  • Continuous flow analysis requires IQC throughout the day. Depends on local policy and with new calibration/reagent lot

You can only guarantee the accuracy of results between acceptable IQC results

Also depends on the analyte

  • Chemistry/Immunoassay
  • Stability of calibration
  • Reagent lot changes

Operator change (manual assays)

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8
Q

What is target value in IQC?

A
  • Precise assays will give different results upon repeat analysis of the same sample
  • Target value is usually defined as the mean +/- 2 standard deviations
  • Standard deviations will vary greatly between different assays
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9
Q

How is the target value determined?

A
  • Need to run up IQC
  • Assayed IQC material is provided with target values
  • Range of values tends to be huge!
  • Assay should be able to perform in a much more reproducible form within controlled conditions of your laboratory
  • New IQC material requires mean to be determined. Usually suggest determining intermediate precision by analysing IQC material 20 times on different days
  • Standard deviation should be checked but should not change between IQC lots
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10
Q

How is the IQC then assessed?

A
  • IQC values within +/-2SD of the mean and report patient results
  • If IQC is > +/-2SD but < +/-3SD, Warning sign – assess the situation (don’t necessarily need to reject the result but assess the assay)
  • If IQC is >+/- 3SD, reject the run

Practice varies between labs

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11
Q

What is systemic error and Random errors?

A

Systematic errors

  • Proportional/Constant Bias
  • Affects accuracy and see a distinctive bias

Random Errors

  • Random deviation from the lab mean
  • Affects precision/reproducibility
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12
Q

What are causes of systematic errors?

A
  • Incorrectly assigned calibrator
  • Calibration lot changes
  • Reagent lot changes
  • Light source deterioration
  • Reagent/calibrator deterioration
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13
Q

What are causes of Random Errors?

A
  • Inaccurate pipetting
  • Analyser mis-sampling
  • Sample contamination
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14
Q

What are types of of random and systematic errors

A

Systematic

  • Proportional
  • Constant
  • Mixed

Random

  • Was there a mistake, inaccurate pipetting?
  • Mis-sampling? – repeat! Be aware, repeated random errors may indicate a problem.
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15
Q

What is Proportional Bias in Systematic Errors?

A
  • A minimum of 2 points are needed - a calibrator and a blank
  • Is your calibrator value correctly assigned?
  • Is the calibrator expired / has it gone off?
  • Has the calibrator been correctly stored?
  • Has the calibrator lot changed without you realising?
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16
Q

How is constant bias investigated?

A
  • Is the assay / analyser working OK – the lamps? the cuvettes The reagents?
  • Is there some positive or negative interference?
  • Is there some contamination?
  • Are the wash steps working correctly?
  • Do you need more wash steps?
17
Q

What are some forms of EQA?

A
  • NEQAS
  • WEQAS
  • IMMQAS
  • RIQAS
18
Q

How is EQA undertaken?

A
  • Receive a set of samples (normally 3 or 4 depending on the scheme). Don’t know the values
  • Processed as normal samples, in order to assess the entire testing process
  • Results reported to the EQA scheme
  • The EQA scheme produces a report
  • You keep a record of all your results in a managed system
  • If you do not meet the performance criteria determined by the EQA scheme, the scheme will warn you, with a letter of poor performance.
  • The schemes have put in place poor performance criteria which expect a 100% return rate.
  • Return rate fail, or non-response to formal SO contact are becoming an automatic panel referral
  • EQA = a constant analytical audit
19
Q

What are the purposes of an EQA?

A
  • Assessment of inter-lab performance: Is a method consistent between labs?
  • Performance between methods: Do different methods perform differently? Possible clinical implications
  • Used in the laboratory quality system:an EQA KPI: the number of poor performance letters received
  • Assessment of trends: e.g rising, falling, repeating pattern, constant positive or negative bias
20
Q

What the steps taken when poor performance isn’t acted upon?

A
  • Local
  • Scheme organiser
  • Panel
  • Joint working group
  • UKAS
  • CQC
21
Q

What are other considerations for EQA use?

A
  • It can be used in method evaluation, to determine accuracy
  • Poor EQA performance across labs using the same method can provide evidence to prompt a company to improve their method
  • When you are looking to purchase a new piece of kit or method, you can check its EQA performance
  • Network reports
22
Q

What are question to ask with poor EQA return?

A
  • What’s the problem? High A score / B score / C score A bias Is it an isolated incident (random error)
  • Is there a pattern? Was there a sudden shift? Is there a trend? What does the bias look like? Proportional (systematic error), Constant (systematic error)
23
Q

How is poor EQA return fixed?

A

A random error? Check the IQC

  • Single random error, was the QC all OK?
  • What does the precision of the assay look like?
  • If this one sample has had a random error, could this be happening at other times?

A poor A/B score? Check the IQC

  • If you have a continuous bias, you are not performing acceptably
  • This should show up in your IQC
  • If not, target and SDs of your IQC should be re-evaluated – the current settings are not picking up issues as they should
  • A poor C score? This reflects the consistency of your bias. Are you always positive / negative, is it always to the same degree? A high C score indicates that your bias has been variable over the last 12 runs.
24
Q

What are different types of bias giving a poor C score?

A

Concentration-dependent bias

  • [low] = positive bias
  • [mid] = no bias
  • [high] = negative bias

A change or shift in bias

  • New calibrator
  • Maintenance
  • Lot change – cal / reagent

Analytical Imprecision

25
Q

What are disadvantages of EQA?

A
  • Only indicates a snap shot in time, difficult to reflect laboratory over all performance.
  • If you are compared against an ALTM and you aren’t the main method it’s difficult to know how well you’re performing
  • When the group is too small – statistical comparison is difficult
26
Q

What is MAPS?

A

Minimal Acceptable Performance Standards

  • The aim is to develop a single scoring system with specific standard for each analyte
  • Started with these 5 analytes
  • Derived from intra- and inter-individual biologic variation data
27
Q

What are current issues with MAPS?

A
  • Different schemes – 34!
  • Different scoring systems – 8!
  • Different scoring criteria
  • Different report formats
  • Different schemes can be more or less ‘difficult’
  • Evidence-based medicine can only be practiced if results are commutable between labs
28
Q

What are advantages and disadvantages of using multi rule IQC?

A

Advantages

  • You miss fewer errors
  • You get a clue to the problem
  • You waste less time and you catch issues quicker – they can then often be resolved more quickly. This can improve turn around times.
  • You save money by highlighting issues more quickly

Disadvantages

  • The recommended rules vary depending on how many QC levels you use and the analyte
  • You need specialist QC software
  • Might you highlight too many issues

MSC: Analytical Methods (13 decks)

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