Lab management Flashcards
What is standardisation?
Trueness based agreement
Comparable results with traceability to a primary reference standard
What is Traceability?
The unbroken chain of calibrations connecting a routine result to a primary reference standard
What is Harmonisation?
Consensus based agreement.
Comparable results without traceability to a primary reference standard
Formula for positive likelihood ratio
sensitivity / (1-specificity)
Formula for negative likelihood ratio
(1-sensitivity)/specificity
What is the Limit of Blank (LoB)?
Highest apparent concentration of analyte free material.
What is the Limit of Detection (LoD)?
Lowest concentration of analyte confidently measured
(Lowest concentration confidently separated from the blank)
What is the Limit of Quantitation (Functional Sensitivity)?
Lowest concentration of analyte reliably measured
What is the definition of Uncertainty of measurement? (as per ISO15189)
Parameter associated with the result of measurement that characterises the dispersion of values
What are the 6 steps of EBLM?
- Ask - frame a PICO question
- Acquire - search the literature
- Appraise - critically review the literature
- Analyse - systematic reviews and meta analyses
- Apply - develop and promote guidelines
- Assess - audit/evaluation
What does PICO question stand for in evidence based laboratory medicine?
Patient
Intervention
Comparator
Outcome
What does STARD stand for?
Standards for Reporting Diagnostic Accuracy studies
Formula for correcting sodium concentration for hyperglycaemia
Na (corrected) = Na (measured)+ Glucose/4
Calculation to estimate VLDL from triglycerides (using mmol/L)
Trig/2.2
Formula for creatinine clearance
(Urinary Cr x Vol)/(Plasma Cr x Time)
What calculations are available to estimate renal function?
Cockcroft and Gault
MDRD formula
CKD-EPI
In pre renal renal failure, what would you expect the fractional excretion of sodium to be?
<1%
Components of a patient based real time quality control system
Calculations algorithm
Block size
Truncation (filtering) limits
Control limits (or rules)
Method validation involves assessing… (name 8 components)
- Accuracy
- Precision
- LoD and LoQ
- Working concentration range (linear range)
- Standard measurement uncertainty
- Interference studies (specificity)
- Stability studies
- Establishing the reference range
Minimum scope for Method Verification
- intra-assay precision and accuracy
- inter-assay precision and accuracy
- correlation with existing method
Statistical test used for non-parametric data to determine if the observed frequencies were as expected?
Chi-squared test
Statistical test used for non-parametric data to determine if 2 measurements for a subject differ significantly?
Wilcoxon Signed Rank Test
Statistical test for parametric data used for answering - is there a difference in the mean of 2 groups of data which is statistically significant?
Students t-test
Coefficient (reported as r) which measures if there is a linear relationship between 2 groups of data.
Pearson’s Correlation Coefficient
Hierarchy of Quality Specifications - Stockholm Criteria
- Studies on clinical outcomes
- Clinical decisions based on BV, clinical opinion
- Published professional recommendations
- Performance goals set by regulatory bodies of EQA schemes
- Goals based on current state of the art as demonstrated by current or EQA data
Milan models for APS
Model 1 - based on effect of analytical performance on clinical outcomes
Model 2 - Based on components of biological variation of the measurand
Model 3 - Based on **state of the art **
Westgard rules that = QC Failure
Do not report patients
1 3S
2 2S
R 4S
Westgard rules = QC warning
1 2S
4 1S
10X
Capability Index =
APS/Sd of assay
What Capability Index is considered acceptable?
> 2 - minimum
3 - desired
4 - excellent
6 - 6 sigma
Measurement of Uncertainty (MU) =
2 x SD of the assay (or CV%)
This gives us a 95% confidence of the “true result”
What does NPAAC stand for?
National Pathology Accreditation
Advisory Council
establish guidelines and standards for accreditation
What does NATA stand for
National Association of Testing Authorities
Types of bias in diagnostic accuracy studies
- Spectrum bias
- Selection bias
- Verification bias
- Blinding
- Publication bias
Strategies to improve testing appropriateness can be classified as (3 categories):
- Restriction
- Feedback
- Education
What is error
Difference between the measured value and the reference value
Optimal specification for imprecision is …
CVa </= 0.25 CVi
Desirable specification for imprecision is …
CVa </= 0.5 CVi
Minimal specification for imprecision is…
CVa </= 0.75 CVi
Milan consensus hierarchy for APS
Model 1 - based on the effect of analytical performance on clinical outcomes
Model 2 - Based on components of biological variation of the measurand
Model 3 - Based on state of the art
What is the Diagnostic Odds Ratio
DOR = (TP/FN) / (FP/TN)
Odds of positivity in subjects with disease relative to odds in subjects without disease
Does not depend on disease prevalence
Nomogram used to calculate post test probability
Fagan nomogram
Definition of Commutability
Property of reference materials
Defined as those materials having the same inter-assay relationships to those of clinical samples
Factors to consider in assessing new lots
- Samples
- Statistics
- Acceptance criteria
- Actions
Steps to assess Clinical Utility
- Review state of the art
- use STARD criteria - Decide an approach to determination
- Design your evalution
- Plan your evaluation
- Decide the levels of evidence that are required
What does JCTLM stand for?
Joint Committee for Traceability in Laboratory Medicine
How does Deming linear regression measure residuals?
Residuals are measured at right angles to the line of best fit
Vs in ordinary linear regression residuals are at vertical
What is the main advantage of Passing Bablok compared to other forms of linear regression?
More robust to outliers as uses medians to calculate slope and intercepts
Lines drawn between all pairs of data points and median slope calculated
Number of samples recommended to calculate LoB or LoD
20 if verifying
60 if establishing
Analytical sensitivity is also referred to as..
The Limit of Detection
Functional sensitivity is also referred to as..
The Limit of Quantitation
ISO standard for POCTs
ISO 22870
