Quality in Haematology Flashcards
What are some of the preanalytical issues to consider when interpreting antibody based, chromogenic and clotting based assays?
- Antibody: presence of atypical antibodies: paraproteins, rheumatoid factor, heterophile antibodies
- Chromogenic: effects of lipaemia and haemolysis. Exogenous anticoagulant drugs.
- Clotting based assays: imprecision due to due to variation in the baseline clotting time and the levels of other factors. Presence of lupus anticoagulant or exogenous anticoagulant drugs.
List some the the pre-analytic errors that can affect outcomes of clotting based assays
• Patient problems
○ Wrong test ordered
○ Sample collected from wrong patient
• Problems with tube ○ Wrong tube ○ Under-filled tubes ○ Citrate concentration ○ Vacuum leak and citrate evaporation
• Problems with phlebotomy ○ Heparin contamination ○ Slow fill ○ Underfill ○ Vigorous shaking ○ Wrong label
• Biological effects
○ Hct ≥55 or ≤15 (changes the ratio of citrate to plasma)
○ Lipaemia, hyperbilirubinemia, haemolysis
• Laboratory errors ○ Delay in testing ○ Prolonged incubation at 37°C ○ Insufficient incubation at 37°C (cryofibrinogen) ○ Freeze/thaw deterioration
Discuss the effects of hyperlipidaemia, haemolysis and hyperbilirubinaemia
- Depending upon the spectra used, all may interfere with the results when optical based methods of clot detection are used
- Hyperlipidaemia leads to an increase in background absorbance, less reliable results obtains when optical methods used
- The spectra used for clot detection is usually outside of the wavelength of haemolysis or hyperbilirubinemia but both of these factors can lead to sample activation and therefore spurious results
List some analytical errors in coagulation testing
- Equipment malfunction
- Reagent issues (i.e. expired)
- Sample mix-ups
- Undetected failure in quality control
- Interference (endogenous/ exogenous)
List some post analytical errors that can occur in laboratory testing
- Erroneous validation of analytical data
- Failure in reporting/ communicating results
- Improper data entry/ transcription errors
- Excessive turn-around time
- Incorrect interpretation
- Inappropriate/ inadequate follow up of result
What are the commonly used commercial controls in coagulation testing?
- Freeze dried human plasma
- May be assayed (normal results provided) or unassayed (lab to determine normal range)
- Usually three controls
1) Normal
2) Abnormal (mild to moderately abnormal)
3) Abnormal (markedly abnormal) - Controls are run at least once a day
What steps should you take when QC is out of range?
• Established policies/ procedures for troubleshooting should be in place.
1) Stop issuing results/ loading new sample
2) Check all components of the test system (QC material, reagents, instrument)
3) Take corrective action
4) Once potential sources of error have been identified and corrections have been made, the control sample should be rechecked.
4) Determine the effect on already issued results
5) Retest as necessary (until a point of agreement between results is reached). The samples should be rerun along with another QC sample.
6) Correct results/ inform appropriate clinician
7) Document what has occurred
What factors can cause out of range QC results with reagents and QC agents
1) Material has deteriorated/ expired
2) Wrong lot number
3) Incorrectly prepared
4) Incorrectly/ inadequately mixed
5) Loaded incorrectly
6) Empty vial/ short sampling
What is quality?
Lab quality can be defined as accuracy, reliability and timeliness of the reported test results
What is a Quality Management System?
Coordinated activities to direct and control an organisation with regard to quality.
What pre-analytical, analytical and post-analytical factors need to be considered when developing a quality management system?
○ Pre-analytical:
- Test selection
- Patient preparation
- Sample collection
- Sample labelling
- Sample transportation
- Sample receipt and accessioning
○ Analytical
- Laboratory analysis and examination
○ Post-analytical
- Report creation
- Result interpretation
- Record keeping
- Report transportation
What are the “12 Quality System Essentials” as per the WHO?
- Organisation
- Personnel
- Equipment
- Purchasing and inventory
- Process control
- Information management
- Documents and records
- Occurrence management
- Assessment
- Process improvement
- Customer service
- Facilities and safety
What is quality control (QC)?
- Component of process control
- Monitors the processes related to the analytical phase of testing
- Allows for the detection of errors in the testing system
- QC gives the laboratory confidence that the test results are accurate and reliable before the patients results are reported.
- QC programmes help differentiate between normal variation and errors.
What are the steps for implementing a QC programme?
1) Establish policies and procedures
2) Train all staff in how to properly follow procedures and policies
3) Assign responsibility for monitoring and reviewing
4) Select a good QC material
5) Establish control ranges for the selected material
6) Develop graphs to plot control values (Levey-Jennings charts)
7) Establish a system for monitoring control values
8) Take immediate corrective action if needed
9) Maintain records of QC results and any corrective actions taken
What are controls? How and why are they used?
- Controls= substances that contain an established amount of the substance being tested- the analyte
- Tested at the same time and in the same way as patient samples
- Validate the reliability of the test system and evaluate the operators performance and environmental conditions that might impact results
How do you establish the value range for the control material?
• The control material is assayed repeatedly, over time
○ At least 20 data points must be collected over a 20- 30 day period.
• Once the data is collected, the mean and standard deviation is calculated
○ This helps establish the normal variability of the test system.
○ This helps determine if a result is due to normal variation or due to error
○ If one or two data points appear to be too high or low for the set of data they should not be included when calculating QC ranges; these are called ‘outliers’
○ If >2 outliers are present, there is a problem with the data and it should not be used.
What does ‘in control’ mean?
• The result of the control is plotted on a Levey-Jennings chart. If the value is within +/- 2SD then it can be accepted as “in control”
What is random and what is systemic error?
• Random error= variation in QC results that show no pattern
○ Generally does not reflect a failure in some part of the testing system and is therefore not likely to recur
○ Random error is only a cause for rejection of the test run if it exceeds +/- 3SD
• Systematic error= variation in QC results that show a pattern
○ Reflect a failure in some part of the testing system and is therefore likely to recur
○The run should be rejected and the cause corrected
What is a shift and what is a trend?
Forms of systemic error:
• Shift: abrupt change in the control mean: when the control is on the same side of the mean for 5 consecutive runs.
• Trend: gradual loss of reliability of the test system: when the control is moving in one direction and appears to be heading toward an out of control value.
What are some of the potential causes for the QC being out of range?
• Possible problems to consider include:
○ Degradation of reagents or kits
○ Control material degradation
○ Operator error
○ Failure to follow manufacturers instructions
○ Outdated procedure manual
○ Equipment failure
○ Calibration errorWhat is EQA?
Method that allows for comparison of a labs testing to a source outside of the laboratory
What are the benefits of EQA?
- Allows comparison of performance and results among different test sites
- Provides early warning for systematic problems associated with kits or operations
- Indicates areas that need improvement
- Enables corrective action to be undertaken where necessary
- Identifies training needs
- Provides objective evidence of testing quality
- Assures clients that the laboratory can produce reliable results.
What are some causes of poor performance in EQA?
• Pre-analytical
○ Sample may be compromised during preparation, shipping or after receipt in the lab by improper storage or handling
○ The sample may have been processed or labelled improperly
• Analytical (should be investigated to determine whether error is random or systemic)
○ Different matrix effects in the examination system used by the participating laboratory
○ Reagents, instruments, tests methods, calibrations and calculation
○ Staff competency
• Post-analytical
○ Report format problems
○ Incorrect interpretation
○ Clerical or transcription errors
What is certification and what is accreditation?
Certification= procedure by which an independent body gives written assurance that a product, process or service conforms to specific requirements.
Accreditation= procedure by which an authoritative body gives formal recognition that a body or person is competent to carry out specific tasks.
Accreditation provides a higher level of assurance to those using the lab that its testing is reliable and accurate because it includes an evaluation of competency.
