Quality Control Flashcards
Is a complete system of creating and following procedures and policies
Quality Assurance (QA)
What is the aim of quality assurance?
To provide the most reliable patient laboratory result
To minimize errors in the pre-analytical, analytical, and postanalytical phases
A system of ensuring accuracy and precision in the laboratory by using quality control materials in every series of measurement
Quality Control (QC)
Testing of patient samples can proceed even without performing QC first. True or false?
False; before you run patient samples, you have to run quality control testing first
Overall process used to ensure that laboratory results meet the requirements for healthcare services to patients
Quality Management (QM)
Quality Management is otherwise known as
TQM (Total Quality Management)
Intervals of acceptable values with upper and lower limits
Control limits
Most commercially prepared QC materials are lyophilized. What does lyophilized means?
They come in powdered or pulverized form
Ideal control limit
± 2SD
Who applied the principles of analyzing QC in the laboratory? When?
Levey & Jennings, 1950s
These are specimens analyzed for QC purposes
Quality Control Materials/ Control Solutions
Control level with concentrations above or below the normal range of the analyte being tested
Level 2 (Abnormal Control)
A sample taken from the total volume of the quality control material
Aliquot
Level of control that contains normal levels for the analyte being tested
Level 1 (Normal Control)
Level of controls commonly used in immunoassays:
Level 1 (Low Control)
Level 2 (Normal Control)
Level 3 (High Control)
What to do if a quality control result shows that one/some values are out of control?
Find the error → take corrective measures → repeat quality control testing = if the control results are within the control limits, you can now proceed testing patient samples
What are the objectives of performing Quality Control?
To check the stability of the machine/analyzers utilized in the Chemistry Laboratory
To check the quality of the reagents
To check technical (operator) errors
The errors we encounter in the laboratory from the pre-analytical, analytical and post-analytical phases of testing
Variation/Variables
In the operation of a QC system, is it allowed to accept errors?
Errors are acceptable BUT WITH LIMIT
The standard confidence limit in Clinical Chemistry is set at
± 2SD
If the error repeatedly occurred (even if corrective actions are already made). Reject or Accept?
Reject
If an error occurred, but it was corrected thru corrective actions. Reject or Accept?
Accept
Involves the analyses of control samples and the patient specimen; use for the daily monitoring of accuracy and precision of analytical methods
Intralab Quality Control (Internal QC)
How often should we perform QC within a clinical laboratory?
Daily
In Intralab Quality Control (Internal QC). Quality Control Materials are: Assayed or Unassayed?
Assayed; values are known and given
Involves proficiency testing programs that periodically provide samples of unknown concentrations to participating clinical laboratories
Interlab Quality Control (External QC)
In Interlab Quality Control (External QC). Quality Control Materials are: Assayed or Unassayed
Unassayed; values are known by the National Reference Laboratories but are NOT given to the participating clinical laboratories
Gold standard for clinical laboratory external QC testing
College of American Pathologists (CAP) proficiency program
Transcribe NEQAS
National External Quality Assurance Scheme
Importance of proficiency testing programs for laboratories
Important in maintaining long-term accuracy of analytical methods
To determine state-of-the-art interlaboratory performance
Reference Laboratory for Microbiology and Parasitology
Research Institute for Tropical Medicine (RITM)
Reference Laboratory for Immunology and Serology
San Lazaro Hospital / STD AIDS Cooperative Central Laboratory (SLH/SACCL)
Reference Laboratory for Hematology and Coagulation
National Kidney and Transplant Institute (NKTI)
Reference Laboratory for Clinical Chemistry
Lung Center of the Philippines (LCP)
Reference Laboratory for Drugs of abuse, Toxicology, Micronutrient Assay, Environmental and Occupational Health
East Avenue Medical Center (EAMC)
These laboratories are mandated to provide laboratory referral services such as confirmatory testing, surveillance and research
Reference Laboratories
Type of laboratory that function to maintain Quality Assurance Programs
Reference Laboratories
The 10 analytes measured/quantified under the NEQAS for CC
- Glucose
- BUN (blood urea nitrogen)
- Creatinine
- Uric Acid
- Cholesterol
- Triglycerides
- Albumin
- Sodium
- Potassium
- Chloride
During NEQAS, what will happen to laboratories that have submitted results outside the confidence limit?
Possible closure of laboratory
It is the ability of an analytical method to measure only the analyte of interest
Specificity
What are the different parameters of quality control?
Sensitivity
Specificity
Accuracy
Precision
Practicability
Reliability
It is the nearness or closeness of the assayed value to the true value or target value
Accuracy
It is the ability if an analytical method to measure the smallest concentration of the analyte of interest
Sensitivity
A pregnancy hormone that is detected in urine and blood of patients who are pregnant
Human chorionic gonadotropin (HCG)
These are used to determine how good a given test is at predicting and detecting the presence of a disease
Diagnostic sensitivity and Diagnostic specificity
It is the closeness of the assayed value to the repeated value
Precision
It is the degree by which an analytical method is easily repeated
Practicability
it is the ability of an analytical method to maintain accuracy and precision over an extended period of time during which equipment, reagents and personnel may change
Reliability
These are used to determine how good a given test is at predicting and detecting the presence of a disease
Diagnostic sensitivity and Diagnostic specificity
Ability of a test to detect a given disease or condition
Diagnostic sensitivity
Ability of a test to correctly identify the absence of a given disease or condition
Diagnostic specificity
Patient has the disease or condition and positive of the test
True positive (TP)
Patient does not have the disease or condition
and negative of the test
True negative (TN)
Patient has the disease or condition but is negative of the test
False negative (FN)
Patient does not have the disease or condition but is positive of the test
False positive (FP)
Formula for Diagnostic Sensitivity
TP/(TP+FN)
Formula for Diagnostic Specificity
TN/(TN+FP)
Error that occur due to chance
Random error
Factors contributing to random error
Instrument
Reagent
Operator
Environmental conditions
(pipetting error, mislabeling in
samples, temperature of analyzer, and improper mixing of sample or reagent)
Error that can influence the observations consistently in one direction
Systematic error
Corrective actions for systematic error
Check on equipment/machines
Check reagents
Check quality control materials
Check standard solutions
Review standard operating procedures
Factors contributing to systematic error
Calibration problems
Deterioration of reagents and control materials
Improperly made standard solutions
Contaminated solutions
Unstable and inadequate reagent blanks
Leaky ion selective electrode
Poorly written procedures
An error where the magnitude of change is constant and not dependent on amount and concentration of analyte
Constant systemic error
Cause of constant error
Interference or contamination
Error dependent on analyte concentration
Proportional error (Slope/Recent error)
Cause of proportional error
Poor recovery of analyte during an analysis
Means that the total error is less that the standard confidence limit, which is ±2 SD, and the performance is acceptable
Allowable analytic error (EA)
Principle of allowable analytic error
If RE and SE (total error) < Ea, then the performance of the test is considered acceptable
What to do if the total error is greater than the allowable error?
Corrections must be made to reduce the error or the method is rejected
Measure of central tendency
Mean
The most frequently used measure of variation
Standard deviation (SD or s)
An index of precision
Coefficient of variation (CV)
Measure of variability
Variance (V)
Bell-shaped curve/Normal distribution curve/Normal frequency curve
Gaussian curve
It is the most widely used QC chart in the clinical laboratory
Shewhart Levey-Jennings Chart
Advantages of Shewhart Levey-Jennings Chart
Can apply multiple rules without the aid of the computer
Easily identifies random and systematic errors
Formed by the control values that continue either to increase or decrease for a period of six consecutive days by passing the mean
Trend
Main cause of trend
Deterioration of reagents
Solution to trend
Open new set of reagent/ QC materials
Criteria for trend
Increase or Decrease for 6 consecutive days (control values)
Control values should pass the mean
Formed by the control values that distribute themselves on one side of the mean for a period of six consecutive days
Shift
Main cause of shift
Improper calibration of the instrument
Solution to shift
Recalibrate instruments
Criteria for shift
Distribute themselves on one side of the mean
6 consecutive days
Are highly deviating values far from the main set of values
Outliers
Rules that are used to further judge whether control results are out of control or in control
Westgard Rules
One control observation exceeds the mean +2SD
1 2S
A warning rule that initiates testing of control data by other rules
1 2S
One control observation exceeds the mean+3SD
1 3S
Rule that allows high sensitivity to random error
1 3S
Two control observations consecutively exceed either the mean ±2SD
2 2S
Rule that allows high sensitivity to systematic error
2 2S
Four consecutive control observations exceed either mean ±1SD
4 1S
Rule that allows the detection of systematic error
4 1S
The range or difference between the highest and lowest control result within an analytical run exceeds +2SD and -2SD
R 4S
Rule that allows detection of random error
R 4S
Ten consecutive control observations are on the same side of the target mean
10X
The 10X rule allows the detection of random or systematic error?
Systematic error
Warning rule for screening purposes
1 2S
Rule/s that detects and with high sensitivity to random error
1 3S
R 4S
Rule/s that detects and with high sensitivity to systematic error
2 2S
4 1S
10X
