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Questions and Answers
What are random or systematic errors related to in measurement?
What are random or systematic errors related to in measurement?
Westgard Rules are applicable in the context of internal quality control procedures.
Westgard Rules are applicable in the context of internal quality control procedures.
True
What is used in IQC procedures to mimic patient samples?
What is used in IQC procedures to mimic patient samples?
Stable control material
A stable control material is analyzed ___ by ___ to monitor the accuracy of testing procedures.
A stable control material is analyzed ___ by ___ to monitor the accuracy of testing procedures.
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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What is the primary purpose of a Levey-Jennings Chart?
What is the primary purpose of a Levey-Jennings Chart?
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Westgard rules are used to assess control within standard limits.
Westgard rules are used to assess control within standard limits.
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What two calculations are necessary to start making a Levey-Jennings Chart?
What two calculations are necessary to start making a Levey-Jennings Chart?
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The ______ is used to display individual measurements plotted against control limits.
The ______ is used to display individual measurements plotted against control limits.
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Match the following terms with their correct descriptions:
Match the following terms with their correct descriptions:
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What is the purpose of computing for ±1, 2, and 3 standard deviations (SD)?
What is the purpose of computing for ±1, 2, and 3 standard deviations (SD)?
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The LJ chart is primarily used for visualizing the mean only.
The LJ chart is primarily used for visualizing the mean only.
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What are the key elements to check when applying Westgard rules?
What are the key elements to check when applying Westgard rules?
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To begin creating an LJ chart, one must first compute the mean and _____ of the data.
To begin creating an LJ chart, one must first compute the mean and _____ of the data.
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Match the following steps with their correct order in creating an LJ chart:
Match the following steps with their correct order in creating an LJ chart:
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What does 'SD' stand for in the context of the chart data?
What does 'SD' stand for in the context of the chart data?
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The graph indicates that Sodium has a value of 200.
The graph indicates that Sodium has a value of 200.
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What is the value of Sodium represented in the LJ chart?
What is the value of Sodium represented in the LJ chart?
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In the LJ chart, Sodium is represented as _____ at +3 SD.
In the LJ chart, Sodium is represented as _____ at +3 SD.
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What does a sodium result of 180 indicate in relation to standard deviations?
What does a sodium result of 180 indicate in relation to standard deviations?
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A sodium result of 140 is considered 3 standard deviations below the mean.
A sodium result of 140 is considered 3 standard deviations below the mean.
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What is the mean sodium result from the given data?
What is the mean sodium result from the given data?
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A sodium result of __________ might trigger a Westgard rule violation if it falls below -2 SD.
A sodium result of __________ might trigger a Westgard rule violation if it falls below -2 SD.
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Match the sodium results with their respective standard deviations:
Match the sodium results with their respective standard deviations:
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What is the main cause of a trend in the analytic process?
What is the main cause of a trend in the analytic process?
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A shift is characterized by a gradual change in the analytic process.
A shift is characterized by a gradual change in the analytic process.
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What defines a shift in the analytical process?
What defines a shift in the analytical process?
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A gradual change in the analytic process is known as a ______.
A gradual change in the analytic process is known as a ______.
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Study Notes
Levey-Jennings Chart
- Used to graph successive quality control (QC) values.
- Employs standard deviations.
- Created individually for each test.
- Decision limits are determined by normal limits (+/- 1, 2, and 3 standard deviations (SDs)).
Mean and Standard Deviation (SD) of QC Material
- X-axis: Time of run.
- Y-axis: Control value.
- Data sourced from the manufacturer.
- Plotting is usually done manually but most automated analyzers plot the charts automatically.
Ideal Levey-Jennings Chart Characteristics
- Control values cluster around the mean.
- Little variation in upward and downward directions.
Imprecision
- Characterized by a large amount of scatter around the mean.
- Commonly caused by errors in technique.
Inaccuracy
- Often exhibits as a trend or shift.
- Typically caused by changes in the testing process.
Random Error
- No discernible pattern.
- Usually due to poor technique or malfunctioning equipment.
QC Chart Review and Documentation
- Regularly review charts to identify issues.
- Take necessary action based on findings.
- Document the actions taken.
QC Chart Errors
1. Trend
- Formed by control values increasing or decreasing consecutively for six days.
- Often a result of reagent deterioration.
2. Shift
- Control values consistently located on one side of the mean for six consecutive days.
- Might indicate transient instrument differences.
- Often caused by improper instrument calibration.
3. Outliers
- Control values significantly deviating from the main data set.
- Stem from random or systematic errors.
Accuracy and Precision
- High Accuracy, High Precision: Values are close to the bullseye and clustered tightly together.
- High Accuracy, Low Precision: Values are close to the bullseye, but scattered.
- Low Accuracy, High Precision: Values are spread out, but clustered together tightly.
- Low Accuracy, Low Precision: Values are spread out and not close to the bullseye.
Westgard Rules
- A set of rules used to assess the quality of control data in analytical processes.
- Specific rules define when quality control measurements are out of established limits.
IQC Procedure
- Uses a stable control material mimicking patient samples, analyzed daily.
- Control values are plotted on a Levey-Jennings chart.
- Analysis checks if the controls are within standard limits using Westgard rules.
How to Make a Levey-Jennings (LJ) Chart
- Calculate the mean and standard deviation (SD) of the control data.
- Compute the ±1, ±2, and ±3 SD values for determining control limits.
- Create the chart.
- Plot the control data on the chart.
- Check for potential issues using Westgard rules.
Shift and Trend
- Trend: Gradual change in the analytical process over consecutive days (6 or more). This can indicate reagent deterioration.
- Shift: Sudden and sustained change in the analytical result in one direction. Often indicates improper instrument calibration.
- Dispersion: Variability of the control values. Increased dispersion can mean instability in the system.
Variables in a QC Chart
- X-axis (Horizontal / Abscissa): Independent variable (Usually time).
- Y-axis (Vertical / Ordinate): Dependent variable (Usually the measured value).
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Description
This quiz covers the essential concepts of the Levey-Jennings chart used in quality control (QC) within laboratory testing. It discusses the significance of mean, standard deviation, and the characteristics of ideal control charts, along with sources of error and imprecision. Test your knowledge on how to effectively interpret and create these charts!
