Levey-Jennings Chart and QC Analysis
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Questions and Answers

What are random or systematic errors related to in measurement?

  • Measurement bias
  • Quality control protocols
  • Precision and accuracy (correct)
  • Calibration strategies

Westgard Rules are applicable in the context of internal quality control procedures.

True (A)

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.

<p>day, day</p> Signup and view all the answers

Match the following terms with their descriptions:

<p>Accuracy = The closeness of a measured value to a standard or known value Precision = The degree to which repeated measurements under unchanged conditions show the same results Random errors = Errors due to unpredictable variations in the measurement process Systematic errors = Errors that consistently occur in the same direction</p> Signup and view all the answers

What is the primary purpose of a Levey-Jennings Chart?

<p>To analyze individual measurements against control limits (D)</p> Signup and view all the answers

Westgard rules are used to assess control within standard limits.

<p>True (A)</p> Signup and view all the answers

What two calculations are necessary to start making a Levey-Jennings Chart?

<p>Mean and Standard Deviation</p> Signup and view all the answers

The ______ is used to display individual measurements plotted against control limits.

<p>Levey-Jennings Chart</p> Signup and view all the answers

Match the following terms with their correct descriptions:

<p>Levey-Jennings Chart = A control chart for individual measurements Westgard rules = Guidelines for control limit assessment Mean = Average of a set of values Standard Deviation = Measure of measurement dispersion</p> Signup and view all the answers

What is the purpose of computing for ±1, 2, and 3 standard deviations (SD)?

<p>To assess the variability of the data (D)</p> Signup and view all the answers

The LJ chart is primarily used for visualizing the mean only.

<p>False (B)</p> Signup and view all the answers

What are the key elements to check when applying Westgard rules?

<p>Error means and standard deviations</p> Signup and view all the answers

To begin creating an LJ chart, one must first compute the mean and _____ of the data.

<p>standard deviation</p> Signup and view all the answers

Match the following steps with their correct order in creating an LJ chart:

<p>1 = Compute the mean and standard deviation 2 = Create the LJ chart 3 = Plot the data in the LJ chart 4 = Check for Westgard rules</p> Signup and view all the answers

What does 'SD' stand for in the context of the chart data?

<p>Standard Deviation (B)</p> Signup and view all the answers

The graph indicates that Sodium has a value of 200.

<p>True (A)</p> Signup and view all the answers

What is the value of Sodium represented in the LJ chart?

<p>200</p> Signup and view all the answers

In the LJ chart, Sodium is represented as _____ at +3 SD.

<p>200</p> Signup and view all the answers

What does a sodium result of 180 indicate in relation to standard deviations?

<p>It is 1 standard deviation above the mean. (A)</p> Signup and view all the answers

A sodium result of 140 is considered 3 standard deviations below the mean.

<p>True (A)</p> Signup and view all the answers

What is the mean sodium result from the given data?

<p>170</p> Signup and view all the answers

A sodium result of __________ might trigger a Westgard rule violation if it falls below -2 SD.

<p>150</p> Signup and view all the answers

Match the sodium results with their respective standard deviations:

<p>190 = +2 SD 180 = +1 SD 160 = -1 SD 140 = -3 SD</p> Signup and view all the answers

What is the main cause of a trend in the analytic process?

<p>Deterioration of reagents (A)</p> Signup and view all the answers

A shift is characterized by a gradual change in the analytic process.

<p>False (B)</p> Signup and view all the answers

What defines a shift in the analytical process?

<p>6 or more consecutive daily values that distribute abruptly.</p> Signup and view all the answers

A gradual change in the analytic process is known as a ______.

<p>trend</p> Signup and view all the answers

Flashcards

Accuracy

How close a measurement is to the true value.

Precision

How close repeated measurements are to each other.

Random Error

Unpredictable fluctuations in measurements that can vary from one measurement to the next.

Systematic Error

Consistent error in the same direction that affects all measurements equally.

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Internal Quality Control (IQC)

A process of monitoring the accuracy and precision of laboratory tests using control materials.

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Levey-Jennings Chart

A control chart used to plot individual measurements, helping visualize trends and detect potential issues in lab testing.

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Westgard Rules

A set of rules used to analyze data on Levey-Jennings charts to determine if a test result is statistically out of control.

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Mean

The average value of a set of measurements.

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Standard Deviation

A measure of how spread out the data is from the mean.

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How to Make LJ Chart

A process involving calculating the mean and standard deviation of a set of data and then plotting them on a graph.

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Standard Deviation (SD)

A measure of how spread out the data points are from the mean. A higher SD indicates more variability.

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+2 SD

Two standard deviations above the mean. Represents a point where data is considered significantly higher than the average.

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+3 SD

Three standard deviations above the mean. Represents a point where data is highly unlikely and may indicate a serious error.

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± 1, 2, 3 SD

The range around the mean within which a certain percentage of data points are expected to fall. ±1 SD covers 68%, ±2 SD covers 95%, and ±3 SD covers 99.7% of the data.

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LJ Chart (Levey-Jennings Chart)

A graphical representation of quality control data, used to track the performance of a laboratory test over time. It helps identify trends and shifts in data that may indicate problems with the testing process.

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What is a 'Shift' in Westgard rules?

A sudden, abrupt change in the analytical process, where 6 or more consecutive daily values are consistently higher or lower than the mean.

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What is a 'Trend' in Westgard rules?

A gradual, consistent change in the analytical process, where the results steadily increase or decrease over 6 consecutive days.

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What is the main cause of a 'Shift' in Westgard rules?

Improper calibration of the analytical instrument or method.

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What is the main cause of a 'Trend' in Westgard rules?

Deterioration of the reagents used in the analytical process.

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What is the purpose of Westgard rules?

To identify and manage potential problems in the analytical process, ensuring accurate and reliable laboratory results.

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LJ Chart

A visual representation of data, often used in quality control to track and analyze process variation.

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Sodium

A chemical element, typically found in various compounds, essential for human health but high levels can be problematic.

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Data Points

Individual measurements or observations collected during a process or experiment.

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Process Variation

The natural variability inherent in any process, even when performed under the same conditions.

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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

  1. Calculate the mean and standard deviation (SD) of the control data.
  2. Compute the ±1, ±2, and ±3 SD values for determining control limits.
  3. Create the chart.
  4. Plot the control data on the chart.
  5. 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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Preparation of a QC Chart PDF

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!

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