5. Mathematical Principles associated With Quality Control #1

What is the primary purpose of quality control (QC) in a clinical laboratory?

To ensure the accuracy, reliability, and consistency of all test results.

What does internal quality control (IQC) monitor?

The accuracy and precision of testing processes carried out in-house.

What is the difference between internal quality control and external quality control?

Internal QC monitors daily performance in the lab, while external QC evaluates the lab's accuracy against other laboratories.

Define Delta Check.

A system that monitors individual patient results by comparing current lab results to consecutive previous results.

What does Gaussian distribution refer to in quality control?

A bell-shaped distribution where most values cluster around the mean.

List two major functions of control specimens in laboratory testing.

1. To monitor accuracy and precision of test results. 2. To detect systematic random errors.

What are the criteria that must be included on a Levey-Jennings chart?

Mean, upper and lower limits, and results plotted over time.

Explain the term 'accuracy' in context of laboratory results.

How close a test result is to the true or accepted value.

What is precision in laboratory testing?

How close repeated measurements are to each other, regardless of their closeness to the true value.

What is the relationship between accuracy and precision?

Accuracy reflects closeness to the true value, while precision indicates consistency of results.

What can cause randomness in QC results?

Technical issues or errors in pipetting.

Explain the function of Levey-Jennings charts in QC.

To visualize quality control data and identify trends, shifts, or outliers.

What should be done if QC results fall outside acceptable limits?

Testing should be paused until the issue is identified and corrected.

In QC, what is meant by a trend?

A gradual, continuous change in QC results over time.

What are the two types of quality control methods described?

Commercial controls and in-house controls.

Define 'standards' in a laboratory setting.

Purified substances of known composition used for calibration.

What is the role of a medical laboratory technologist in quality control?

To prepare, run and evaluate quality control samples to ensure accuracy and reliability.

What should be included in preventative maintenance activities for lab equipment?

Regular checks in accordance with established protocols.

What are potential errors that Delta Checks may identify?

Specimen mix-ups, mislabeling errors, and sample contamination.

How often should control samples be tested to ensure QC?

At least once per run or batch of tests.

What is the relationship between control limits and patient testing?

Testing must be halted if results are out of control limits.

List the advantages of using in-house pooled specimens.

Cost-effective and relatively easy to prepare.

What limitations may exist with in-house pooled specimens?

Potential hazard of human derivatives and lack of standardization.

What is the definition of systematic errors in quality control?

Consistent errors that affect all measurements in the same manner.

What is a blind duplicate control?

A patient control that involves replicating or splitting a sample without bias during testing.

Describe the term 'assayed controls' in QC materials.

Commercially prepared controls that provide validated, targeted results for multiple analytes.

What is the importance of baseline QC measures?

To ensure measurements reflect the true performance of analytical processes.

What is the overall goal of quality control measures in the laboratory?

To maintain the accuracy and precision of laboratory test results.

How does QC work with control samples?

QC samples are run alongside patient samples and compare results to established ranges.

What constitutes an 'out of control' result in QC terms?

Values that exceed the upper and lower control limits.

What defines a commercial control in laboratory settings?

Standardized materials with known target values for consistent quality assurance.

When should corrective action be taken in response to QC results?

When results indicate an error or a deviation from expected performance.

What is the purpose of quality control in laboratory testing?

To confirm that test results accurately reflect the true value of the analyte being measured.

Explain the significance of the standard deviation in quality control decisions.

It helps to assess the variability of test results and determine the acceptability of the data.

What is the difference between accuracy and precision in laboratory results?

Accuracy is closeness to a true value, while precision is the repeatability of results.

What is the role of inventory maintenance in a laboratory?

To manage laboratory supplies effectively, ensuring availability when needed.

Define the term 'dispersion' in laboratory quality control context.

The measure of variability in a set of data points.

What condition should QC materials meet for effective use?

They should mimic patient samples in composition.

Why are delta checks important in laboratory settings?

They distinguish true physiological changes from laboratory errors.

What should be documented after conducting a delta check?

Clerical checks, sample inspections, and any actions taken.

How are QC results evaluated according to the Westgard Rules?

By applying control limits based on the mean and standard deviation.

What is the importance of calibration in laboratory testing?

To ensure methods and instruments measure correctly.

How is reflective practice applied in quality control?

By analyzing actions and decision-making processes to improve future practices.

What is a critical aspect of QC regarding laboratory reagents?

Confirmation that reagents are not expired or contaminated.

What does the term 'controls' refer to in laboratory testing?

Materials similar to patient samples used to monitor test performance.

Define the concept of trending in quality control analysis.

Observed changes in QC results over time that suggest an issue.

What constitutes a valid method evaluation in a laboratory?

Assessing whether methods passed specified performance criteria.

Why is it important to document lot numbers and expiry dates for quality control materials?

To ensure traceability and proper usage of materials.

What determines whether results can be reported after a quality control failure?

If the controls are within acceptable limits after troubleshooting.

Explain the importance of statistical methods in quality control.

To monitor and track the acceptability of quality control results.

What types of QC materials provide manufacturers' target values?

Assayed controls.

What is the difference between unassayed controls and assayed controls?

Unassayed controls lack target values, while assayed controls provide validated results.

Why is it crucial to compare patient results against established QC criteria?

To ensure the accuracy and reliability of reported results.

What is the expected outcome if proper QC protocols are followed?

Reliable and accurate laboratory test results.

What role do external quality controls play in laboratory practice?

They provide an evaluation of a laboratory's performance against peers.

How can systematic errors be detected in quality control?

By comparing results to external QC data and identifying discrepancies.

When is it acceptable to report patient results during QC failures?

Only after all corrective actions have been taken and quality control measures verified.

What is the purpose of a control chart in laboratory quality control?

To track results over time and assess the stability of the testing process.