Quality Control Flashcards by Eldren Joi Malsi

Is a complete system of creating and following procedures and policies

Quality Assurance (QA)

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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

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A system of ensuring accuracy and precision in the laboratory by using quality control materials in every series of measurement

Quality Control (QC)

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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

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Overall process used to ensure that laboratory results meet the requirements for healthcare services to patients

Quality Management (QM)

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Quality Management is otherwise known as

TQM (Total Quality Management)

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Intervals of acceptable values with upper and lower limits

Control limits

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Most commercially prepared QC materials are lyophilized. What does lyophilized means?

They come in powdered or pulverized form

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Ideal control limit

± 2SD

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Who applied the principles of analyzing QC in the laboratory? When?

Levey & Jennings, 1950s

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These are specimens analyzed for QC purposes

Quality Control Materials/ Control Solutions

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Control level with concentrations above or below the normal range of the analyte being tested

Level 2 (Abnormal Control)

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A sample taken from the total volume of the quality control material

Aliquot

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Level of control that contains normal levels for the analyte being tested

Level 1 (Normal Control)

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Level of controls commonly used in immunoassays:

Level 1 (Low Control)
Level 2 (Normal Control)
Level 3 (High Control)

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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

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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

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The errors we encounter in the laboratory from the pre-analytical, analytical and post-analytical phases of testing

Variation/Variables

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In the operation of a QC system, is it allowed to accept errors?

Errors are acceptable BUT WITH LIMIT

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The standard confidence limit in Clinical Chemistry is set at

± 2SD

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If the error repeatedly occurred (even if corrective actions are already made). Reject or Accept?

Reject

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If an error occurred, but it was corrected thru corrective actions. Reject or Accept?

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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)

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How often should we perform QC within a clinical laboratory?

Daily

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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

1. Glucose 2. BUN (blood urea nitrogen) 3. Creatinine 4. Uric Acid 5. Cholesterol 6. Triglycerides 7. Albumin 8. Sodium 9. Potassium 10. 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