L1 - Quality Assurance Flashcards
What are the three general sources of error in biochemical analysis based on time-scale?
At what stages in the process of analysis do these occur?
Pre-analytical - before sample gets to the lab
Analytical - during analysis
Post-analytical - what happens to the results
Give three sources of pre-analytical errors
Poor sampling technique, inappropriate containers, storage or transport, not enough sample, errors in patient ID
How can pre-analytical errors be minimised?
Training staff who are to be taking samples, get receptionists to check samples, use barcodes to prevent errors in patient ID
Give three sources of analytical errors
Poor precision/random errors, poor accuracy/systematic errors, poor quality assurance
How can analytical errors be minimised?
Automation, method validation, quality procedures
Give three sources of post-analytical errors
Errors in collation or recording of results, inappropriate reference ranges
Define accuracy
Ability to measure the true value
Define precision
Ability to produce consistent results
Define sensitivity
Ability to identify those with a condition (fewer false-negatives)
Define specificity
Ability to exclude those without a condition (fewer false-positives)
Define analytical sensitivity
Smallest amount of analyte a test can distinguish from zero
Define analytical specificity
Ability to measure only the analyte in question
What are the two types of error in biochemical analysis?
Systematic error and random error
Define systematic error
Are these precise or accurate?
Values are systematically too high OR too low
Precise
Define random error
Are these precise or accurate?
Results are scattered
Accurate
Give an example of a systematic error
Zero error - not zeroing equipment before use means all results are off by the same amount
Give an example of a random error
Human errors such as inconsistent techniques
What are the two types of quality assurance programmes?
Internal Quality Control (IQC)
External Quality Assessment (EQA)
What do internal quality control measures consist of?
Measuring IQC materials (substances with known concentrations of analyte) against samples
What does external quality control consist of?
External bodies collect data on lab performance and compare to other labs to determine if there are any problems
What is a clinical audit?
A review process that aims to improve quality of care
What are the Westgard rules used for?
What does a 1, 2S rule mean?
Rules that help labs to determine if there are problems with the accuracy of their procedures
1 control measure lies outside 2SD of the mean
Define a reference range
Range of values associated with healthy individuals
Central 95% within 2SD of the mean
Give five factors that can affect the reference range used
Age, sex, diet, smoker, pregnancy, stress, exercise timing of sample collection
