(M) Lec 1: Quality Management in Clinical Chemistry Flashcards
Refers to over all program or system that ensures that the final results
generated by the laboratory has achieved and maintained a specified quality
Quality assurance
3 phases of quality assurance
Pre-analytical, Analytical, Post-analytical
These refer to which phase of QA:
Requisition of laboratory test
Patient preparation
Specimen collection
Specimen handling, processing, storage
Pre-ana
These refer to which phase of QA:
Specimen analysis
Quality of reagent
Efficiency of instrument
Analytical skill proficiency of MedTech
Analytical
These refer to which phase of QA:
Interpolation of results
Reporting of Results
Recording of Results
Post-ana
Process of monitoring the characteristics of the analytical processes and detect analytical errors during testing
Quality control
What does QC aims to ensure?
Precision and accuracy
The objective of this is to:
Check quality of reagents
Monitor stability of machine
Monitor personnel errors/technical errors
QC
T or F:
Quality control is defined as the overall program that ensures that final results reported by the laboratory are correct
False (QA)
T or F:
Quality control refers to the measures that must be included during each test run to verify that the test is working properly
True
This aims to ensure that the results generated by the tests are correct
Quality control
What is the overall program that ensures that final results reported by the laboratory are correct?
QA
What are the types of QC?
- Internal/ Intralaboratory Quality Control
- External/ Interlaboratory Quality Control
Refers to:
Precision of laboratory tests
Applied to all work processes and to every test done in the laboratory
Based on the results of control specimens and patient `specimens
Internal/Intralaboratory QC
These refer to:
Pattern recognition
Delta Check
Randomized duplicate specimens
Average of normals
Internal/Intralaboratory QC
Refers to:
Accuracy of laboratory tests
Proficiency testing programs
External/Interlaboratory QC
Ability to recognize pattern
Pattern recognition
Compares past and present result
Delta check
One patient sample is divided into two; requires that the result of the two specimen must be the same to ensure precision
Randomized duplicate specimens
In external QC, where is the sample coming from?
Reference lab
Ref lab for CC
Lung Center of the Philippines
T or F:
Difference of >1 in external QC means not agreement with other lab
False (diff of >2)
Ability of an analytical method to measure the smallest concentration of the analyte of interest
Analytical sensitivity
Ability of an analytical method to measure only the analyte of interest
Analytical specificity
T or F:
Analytical sensitivity and analytical specificity are the same as diagnostic specificity and sensitivity
False
Nearness or closeness of the assayed value to the true or target value
Accuracy
Ability of an analytical method to give repeated results on the same sample
Precision
Reflects reproducibility
Precision
T or F:
In theory: It is impossible to have a method that is accurate but imprecise, but the overall average of repeat values is near the true value
False (possible)
T or F: In Practice: If a method is
imprecise, it is usually also
inaccurate
True
Degree by which a method is easily repeated
Practicabiltiy
Ability to maintain accuracy and precision over an extended period of time
Reliability
Ability to detect the proportion of individuals with a disease who test positively with the test
Diagnostic Sensitivity
Ability to detect the proportion of individuals without the disease who test negatively with the test
Diagnostic Specificity
Difference between the measured value and the mean expressed as a number of SD
SD Index
What are the three SD Index?
SDI of O- accurate/100% agreement
SDI of 3- inaccuracy
SDI of 2- investigate action
SDI that refers to accurate/100% agreement
SDI of O
SDI that refers to inaccuracy
SDI of 3
SDI that refers to investigate action
SDI of 2
These refer to:
Resembles human sample
Inexpensive and stable for long periods
No communicable disease
No matrix effects/known matrix effects
With known analyte concentrations
Convenient packaging for easy dispensing and storage
Preferrable lyophilized
Characteristics of a QC material
Lyophilized control solution must be stored in which temperature?
Room temp
T or F:
Control solution is a sample of known quantity of all analytes
False (several analytes only)
What is run alongside patient samples?
Control solution
2 levels control solution
Level I
Normal
2 levels control solution
Level II
Abnormal
3 levels control solution
Level I
Low normal
3 levels control solution
Level II
High normal
3 levels control solution
Level III
Very abnormal
T or F:
Control solution can be commercially and noncommercially prepared
True
Familiarize the sources of control slution
Fasting donor
Blood bank plasma
Left-over sera
Abbatoir blood
Refers to:
Contains a known amount of
analyte
A specific analyte is present
Used for calibrating an assay
method
Standard solution
Ussed to read out any absorbance caused by reagent or serum
Blank solution
Types of blank solution
Test or Serum blank
Reagent blank
Water blank
Variations/types of errors
Random Error
Systematic Error
Clerical Error
Also called as interdeterminate error
Random error
› Measures “imprecision”
› Errors that occurs without any real pattern
› Causes: due to instrument, operator, and environmental conditions
Random error
The following causes which type of error?
Pipetting errors
Mislabeling of samples
Temperature fluctuation
Improper mixing of sample and reagent
Dirty optics
Voltage fluctuations
Random error
Also called determinate error
Systematic error
› Measures “ Inaccuracy”
› Error that is continuous and affects all results equally
› Measure of agreement between the measured quantity and
true value
Systematic error
The following causes which type of error?
Calibration problems
Deterioration of reagents and control materials
Unstable and inadequate reagent blanks
Contaminated solutions
Failing instrumentation
Poorly written procedures
Systematic error
Two variations/types of systematic error
Constant error
Proportional error
Systematic error that is not dependent on the amount of analyte present
Constant error
Systematic error that is dependent on analyte concentration
Proportional error
Type of error that includes handwritten labels and request forms
Clerical error
T or :
Clerical errors occur in pre-analytical, analytical, and post-analytical phase
True
Refers to:
› Measure of central tendency
› Average of all the data points or values
Mean
Middle data point observed once data are arrange in descending or ascending order
Median
Value that occurs with the greatest frequency
Mode
Difference between the highest and lowest values in a set of data
Range
Measure of variability
Variance
Measure of the average squared distance of data points from the mean
Variance
Measure of precision
Standard dev
Measure of the dispersion of values from the mean
Standard dev
Percentile expression of the mean
Coefficient of Variation
Total Percent Error
Coefficient of Variation
Index of precision
Coefficient of Variation
Limits between which we expect a specified proportion of
population to lie
Confidence intervals or limits
Familiarize the usual confidence limits
68.2%= +/- 1SD
95.5 %= +/- 2SD
99.7%= +/- 3SD
T or F:
To be precise, the mean should be near the individual results
False (accurate)
T or F:
To be precise, the individual results should be near each other
True
What are the measures of precision?
SD, CV and variance
Relationship between SD and precision
Inversely proportional (the higher the SD, the less precise it is)
Relationship between variance and precision
Inversely proportional (the higher the variance, the less precise it is)
Relationship between COV and precision
Inversely proportional (the higher the COV, the less precise it is)
What are the quality control charts?
Gaussian Curve
Cumulative Sum Graph
Youden/Twin Plot
Shewhart Levey-Jennings Char
Refers to Normal Frequency Curve, Normal Distribution Curve
Gaussian Curve
The curve that results from the data that have a
normal distribution forming a bell-shape
Gaussian Curve
Other name for Gaussian Curve
Bell-shaped Curve
Population of subject of Gaussian Curve
At least 100
T or F: In the Gaussian Curve, data elements are centered around the mean with most elements close to the mean
True
Refers to a probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean, and is also known as the Gaussian distribution
Normal Distribution
This gives the earliest indication of systematic error
Cumulative Sum Graph
This calculates the difference between Qc results and the target means and is done by subtracting the mean from the individual values and the cumulative differences are plotted
CUMSUM
Refers to:
Twin Chart
Used to compare results
Used to compare method using different samples or one sample using two different methods
Youden/Twin Plot
Refers to:
Most widely used system in clinical laboratories
Allows laboratorian to apply multiple rules without the aid
of computer
Shewart Levey-Jennings Chart
A graphic representation of the acceptable limits of variation in the results of an analytical method
Shewhart Levey-Jennings Chart
What error is being detected in Shewart Levey-Jennings Chart?
Both random and systematic error
System that allows good visual representation of precision and
relative accuracy, easy to interpret
Shewhart Levey-Jennings Chart
Error detected by Youden Chart?
Systematic error
Error detected by CUMSUM
Systematic error
A Shewhart Control Chart depend on the use of how many QC specimen?
1
Familiarize how Shewhart Control Chart is being developed
Put up the 1QC specimen for atleast 20 or more assay runs and record down readings
Calculate the mean and standard deviations (SD)
Make a plot with the running day on the x axis and readings on the y axis
Draw the lines across the y axis for the following:
Mean, +/- 1SD, +/- 2SD, +/- 3SD
Plot the reading obtained for the 1 QC specimen for `subsequent assay run
What are the errors that ca be observed on LJ Chart?
Trend, Shift, Oulier
Error on LJ Chart that refers to:
Gradual change in the mean that proceed in one direction
Control values either increases or decreases for six consecutive days
Causes: Deterioration of reagents, light source, control materials
Trend
How many days can control values increase or decrease for it to be considered a trend?
Six consecutive days
Causes of trend as an error on LJ Chart?
Deterioration of reagents, light source, control
materials
Error on LJ Chart that refers to:
An abrupt change in the mean that becomes continuous
Control values that distribute themselves on one side or either side of the mean for six consecutive days
Causes: improper calibration of instrument, new lots of standards and reagents
Shift
How many days can control values distribute themselves on the sides of the mean for it to be considered as a shift error on LJ Chart?
Six consecutive days
Causes of shift as an error on LJ Chart?
improper calibration of instrument, new lots of
standards and reagents
Error on LJ Chart that refers to:
Control values that are far from the main set of values
Highly deviating values
Random or Systematic errors
Outlier
Set of control and patient specimens assayed, evaluated and reported together
Analytical Run
Current results compared to the previous/past result
Delta Check
Measured concentration is equal to the actual concentration
Linear Range/Dynamic Range
Analytical testing performed outside the confines of the central lab usually by non-laboratorian personnel
Point of care Testing
Used to measure systematic errors or inaccuracy caused by substances other than the analyt
Interference Experiments
Example of substances that can cause inaccuracy in Interference Experiments
Hemoglobin, Lipids, bilirubin, anti-coagulants
This experiment shows wether a method measures all the analytes or only part of it
Recovery Experiment
This refers to the usual values for a healthy population that represents 95% central tendency
Reference Limit, Reference Interval, Reference Value
Its purpose is to determine how much of analyte can be detected in presence of all other compounds in the matrix
Recovery studies
T or F: Recovery studies determine if the method is able to accurately measure an analyte
True
T or F: In Reference Value, specific measurement are performed on a large number of healthy individuals (age and sex)
True
How many patients do you need each age and sex category to establish a Reference Value/Reference Interval?
100/120
Familiarize the factors that affect establishing Reference Values
Analytical method used
Specimen collection procedure
Composition of reference population
Criteria of exclusion and inclusion
Physiologic and environmental factpr
Refers to:
A new method is evaluated by comparing it with a reference method
Comparison of Methods
T or F:
Westgard recommends that at least 30 samples and preferrably 120 samples should be run by both method
False (40 - 100)
What are the measures of accuracy?
Recovery experiment
Interference studies
Patient sample
comparison
Enumerate the measures of precision.
CV
SD
Variance
Multiple quality control
Westgard’s Multirule System
In Westgard’s Multirule System, this is to indicate if the analytical process is “in
control” or “out of control”
Control rule
What are the control rules in Westgard’s Multirule System?
1-2s
1-3s
2-2s
4-1s
R-4s
10x
subscript yang after ng hyphen idk asan subscript dito
Westgard Control Rules
One control result exceeds the mean by
more than +/- 2SD
Warning or rejection rule
Detects random error
1-2s
Westgard Control Rules
One control result exceeds the mean by
more than +/- 3SD
Detects random error
1-3s
Westgard Control Rules
Two consecutive control results exceed the
mean by 2 more than 2SD
Response most often to systematic errors
Must lie in the same direction from the mea
2-2s
Westgard Control Rules
Four consecutive control results exceeds the
mean by more than 1SD
Must lie in the same direction from the mean
Responsive to systematic error
4-1s
Westgard Control Rules
Difference between two consecutive controls is greater than 4SD
Assay values in opposite direction from each other
Responsive to random errors or increased imprecision
R-4s
Westgard Control Rules
Ten consecutive results are on the same side of `the target mean
Systematic error
10-x
T or F:
If QC is out of control, you can still fix it by testing and testing again
False (stop testing)
T or F:
Each part of the gaussian curve is the percentage per SD
True
In Gaussian curve/bell curve, what could it mean if it lies between 2-3 SD?
Potential error
In Gaussian curve/bell curve, what could it mean if it lies more than 3 SD from the mean?
Needs corrective action
T or F: If the curve becomes wider or skewed, it’s still in normal distribution
False (there is an error)
Disadvantage of Shewart Levey Jennings Chart
Time consuming
Other name for Shewart Levey
Dot/shoe chart
How many directions does the trend proceed to?
One
Trend and shift are example of (random/systematic) errors
Systematic
T or F: A change in the control value for 10 days can be considered either a trend or shift depending whether it’s abrupt or gradual and its direction
False (does not follow 10 x rule)
T or F: A change in the control value for 5 days can be considered either a trend or shift depending whether it’s abrupt or gradual and its direction
False (does not follow the 6 day rule)
In what manner should Confidence limits should be reported?
By range
Which systematic error does CUSUM specifically detect?
Trend
Most common method of CUSUM
VMAS
Which systematic error does Twin Plot specifically detect?
None (not specific)
Most important statistical parameters under LJ Chart
Mean, SD, and CL
In LJ Chart, running day is plotted on (X/Y axis)
X axis
In LJ Chart, reading is plotted on (X/Y axis)
Y axis
In LJ Chart, what are calculated?
Mean and SD
In LJ Chart, what are drawn across the y axis?
Mean, +/- 1SD, +/- 2SD, +/- 3SD
LJ Chart is mostly done with what curve on the side?
Gaussian curve (to check if may bell shape pa rin)
T or F: You cannot use different kinds of lines to differentiate mean from 1SD, 2SD, etc
False (up to you)
T or F: Shift passes the mean in LJ chart
False (papuntang gilid lang)
T or F: Trend goes on sides of the mean in LJ chart
False (Shift ‘yun)
A value must pass how many SD from the mean for it to be considered as outlier usually?
+/- 3SD