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ChemistryLevy-Jennings Charting - Guidelines

Chemistry Levy-Jennings Charting / Guideline Number / Pro51-13-G
Effective Date / 30 Jan 06
Subject
Chemistry Levy-Jennings Charting Guidelines / Page / 1 of 2
Supersedes / New
Review by / Heidi Hanes / Review date / 7 Feb 2012
SMILE Comments: This document is provided as an example only. It must be revised to accurately reflect your lab’s specific processes and/or specific protocol requirements. Users are directed to countercheck facts when considering their use in other applications. If you have any questions contact SMILE.

Audit:

Test and Control Article

CAP Accreditation Checklist:

NA

Background Information:

The following summarizes the procedure for using an Excel worksheet to plot three levels of internal chemistry controls. The Excel spreadsheet should not take the place of a control log but should only be used to create a Levy-Jennings plot. A line plot is used, as apposed to a scatter plot, to track values that might fall outside the range of the graph and help highlight bias, shifts and trends.

Definitions:

  • Year: The year that the controls are run.
  • Month: The month that the controls are run.
  • Day: The day of the month that the controls are run.
  • Control Number: The ascending unique number given to a control run on a specific date for a given lot number.
  • Level 3: The value resulted from the analyzer for the high control.
  • Level 2: The value resulted from the analyzer for the normal control.
  • Level 1: The value resulted from the analyzer for the low control.
  • Mean: This is the mean value for the specific level of control. This can be derived either from the package inserts or determined by the site for a particular lot number.
  • SD: This is the standard deviation from the mean determined for the specific control. This can be derived either from the package inserts or determined by the site for a specific lot number. The chemistryLevy-Jennings chart utilizes the following SD abbreviations:
  • + 1SD: Plus or minus 1 standard deviation
  • + 2SD: Plus or minus 2 standard deviation
  • + 3SD: Plus or minus 3 standard deviation
  • Control graphs: These are the Levy-Jennings plots for values resulted from the analyzer for the Level 3, Level 2, and Level 1 controls highlighting the mean (in a thick, black line) and the standard deviations (+ 1SD has a gray line; +2SD has a red line; and +3SD has a white line). The values for the mean and standard deviations will be entered in the table to the right of the graph and the line will automatically appear on the chart.
  • Lot #: This is the lot number for the kit for the controls that were used.
  • Icon: A small picture.
  • Curser: The arrow or line representing where the mouse is or where information is being put.
  • Cell: A location in a spreadsheet. Each cell has a unique “name,” made up of a letter (for the column) and a number (for the row). The cells are where information will be entered.
  • Table: A group of information and values in a spreadsheet.

Where to get Mean and SD Values

The mean and standard deviation values can be obtained by two sources. First, they can be found in the control insert that accompanies each container of controls. It is also possible for a lab to determine the mean and SD for their own machine by running the controls at least 10 separate times (i.e., the controls are mixed/made/run on 10 separate runs) and then calculating the mean and SD values.

Calculations

The spreadsheet automatically calculates the following parameters:

  • Mean – This is the mean (or average) of all the values obtained for a given control value. The mean of each control value is calculated. The mean is determined by the following formula:

Mean (or average) = (A+B+C+D….etc)/N

Where N = the total Control Numbers

SD – The spreadsheet calculates 1 and 2 SD of the values obtained for a given control value. SD is calculated for each control value by the following formula:

  • %CV – The percent coefficient of variation is determined for the values obtained for a given control value. %CV is calculated for each control value by the following formula:

%CV = (1SD / Mean) X 100

Resources

NA

ChemistryLevy-Jennings Charting - SOP

Author(s), Name & Title / Erin Gover, BA / Document Number / Effective Date
Pro51-13-SOP / 13 Jan 06
SMILE Comments: This document is provided as an example only. It must be revised to accurately reflect your lab’s specific processes and/or specific protocol requirements. Users are directed to countercheck facts when considering their use in other applications. If you have any questions contact SMILE.
Approved By / Name, Title / Signature / Date
SOP Annual Review / Name, Title / Signature / Date
Revision History / Version # [0.0] / Revision Date [dd/mm/yy] / Description (notes)
Distributed Copies to / Name (or location) / # of copies / Name (or location) / # of copies

Associated Forms:

I acknowledge that I have read, understand and agree to follow this SOP.

Name (print) / Signature / Date

Purpose

This procedure ensures the proper use of an Excel spreadsheet to plot chemistry control information.

Procedure

The procedures below may or may not be necessary to customize and organize the lab’s Levy-Jennings charts. Organize the procedures by relevance as they pertain to the lab.

As each chart is copied, it is important to conduct a quality check on calculations and graphed items. First, verify that all calculations are still accurate. This includes not only the formula is written correctly but also that all cells to be calculated are included. In addition, all items being graphed should be verified. This includes the Control Numbers, control values, mean and all SDs.

  1. Rename Tabs: Rename the tabs the same as the analytes being run. The template has many commonly used analytes already present. If there are tabs that will not be used (i.e., analytes are not run in the lab), these can be renamed. (Note: When renaming tabs make sure all areas in the cart and table to the right of the chart are also renamed.) Follow the steps in the table below to rename tabs.

Step / Action
1 / Right click on the tab.
2 / Select “Rename” from the menu.
3 / Type in the name of the analyte as the new name for the tab.
4 / Press “Enter” to save change.
  1. Creating New Worksheets: If there are no more empty tabs at the bottom and additional tabs are needed, a new worksheet must be added. Follow the steps in the table below to create a new worksheet.

Step / Action
1 / NOTE: The new worksheet will be added before the worksheet that is selected.
2 / Select the tab after where the new worksheet should go.
3 / Click on “Insert” from the tool bar at the top.
4 / Click on “Worksheet” from the menu. The new worksheet will be added.
5 / Rename the tab. (See Rename Tabs section above for directions.)
  1. Copying Worksheet into a New Spreadsheet: There is an advantage to copying an existing worksheet (preferably blank) into a new file: all the work is done to create the tables, and graphs will not need to be done again. There are two ways this can be done: 1.) Into a new tab in the same file or 2.) Into a new file. Generally, a new file will need to be created each month or when the lot changes (and, therefore, the means and SD also change).
  2. Copying a worksheet into an existing file

Step / Action
1 / Be sure that there are empty worksheets in the file (refer to Creating New Worksheets.)
2 / Open the worksheet that you want to copy by clicking on the tab at the bottom of the page.
3 / Highlight the entire worksheet. This is done by clicking on the blank cell just above the number 1 and to the left of the A (this is the very first cell of the worksheet).
4 / Click on “Edit” from the toolbar.
5 / Select “Copy” from the menu.
6 / Open the worksheet where you want to place the file by clicking on the tab at the bottom of the page.
7 / Select the cell located at A1 in the upper left hand corner.
8 / Click “Edit” from the toolbar.
9 / Select “Paste” from the menu.
10 / If / Then
The worksheet was not blank. / Delete any data that does not apply to the new lot information:
  • Mean and SD for all controls
  • Month and day controls were run
  • Values for controls

  1. Copying a worksheet into a new file

Step / Action
1 / Open the worksheet that you want to copy by clicking on the tab at the bottom of the page.
2 / Highlight the entire worksheet. This is done by clicking on the blank cell just above the number 1 and to the left of the A (this is the very first cell of the worksheet).
3 / Click on “Edit” from the toolbar.
4 / Select “Copy” from the menu.
5 / Click on the “New Blank Document” icon just below the toolbar. This icon looks like a blank sheet of paper and is found just to the left of the folder icon. This will open a new worksheet in a new file.

6 / Select the cell located at A1 in the upper left hand corner.
7 / Click “Edit” from the toolbar.
8 / Select “Paste” from the menu.
9 / If / Then
The worksheet was not blank. / Delete any data that does not apply to the new lot information:
  • Mean and SD for all controls
  • Month and day controls were run
  • Values for controls

10 / Save the new file before closing and give it a unique name but one that will be easy to recognize. (See Naming a New File below for details.)
  1. Naming a New File

Step / Action
1 / While the file is open, click on “File” from the toolbar.
2 / Select “Save as” from the menu.
3 / Select the folder where the file should be saved.
4 / Enter the file name at the bottom of the “Save As” screen. (Suggestion: LJ Chemistry January 2007)
5 / Click on “Save” to finish creating the new file.
  1. Updating Axis Values and Adding More Control Numbers: If axis values need to be changed or more control numbers need to be added, several parameters need to be updated to ensure that the Levy-Jennings plots are accurate. One or more of the following parameters may have to be updated: Y-axis scale, X-axis values, Y-axis values, and range for calculations. Although not all parameters might have to be adjusted, all parameters should be verified for accuracy.
  2. Changing Y-axis scale (analyzer values)

Step / Action
1 / Click one time on the Y-axis. This will highlight that axis.
2 / Right click while the curser is still on the same axis.
3 / Select “Format axis” from the menu.
4 / Choose the second tab at the top of the window, “Scale.”
5 / Enter in new values for the “Maximum” and “Minimum” values.
6 / Click on “OK” to save these changes (the changes will take place immediately).
  1. Changing X-axis values (control number): If there are more than 45 runs for one control lot number, enter the necessary Control Numbers into the spreadsheet first. So these values will not have to be changed everyday, it might be helpful to add 10 at a time (so for the first time, extend the values to a Control Number of 55).

Step / Action
1 / Right click anywhere in the center of the graph.
2 / Select “Source Data.”
3 / Chose the second tab at the top of this window, “Series.”
4 / Just below the small picture of a graph in the window, there are three lines. To make changes to the X-axis, click on the small icon of a spreadsheet on the third line (labeled “Category (X) axis label”). This will take you to the “source data,” or the Control Number column on the spreadsheet.
5 / Using the mouse, click and drag the curser so the entire column of numbers (including the ones that have been added) are highlighted.
6 / Press the “Enter” key on the keyboard when this is done. This will take you back to the previous window.
7 / Click on “OK” to save these changes.
8 / Repeat on the graphs for all levels of controls.
  1. Changing Y-axis values (analyzer values)

Step / Action
1 / Right click anywhere in the center of the graph.
2 / Select “Source Data.”
3 / Chose the second tab at the top of this window, “Series.”
4 / Just below the small picture of a graph in the window, there are three lines. To make changes to the Y-axis, click on the small icon of a spreadsheet on the second line (labeled “Values”). This will take you to the “source data,” or the Control Results for that level of controls on the spreadsheet.
5 / Using the mouse, click and drag the curser so the entire column of cells (including the ones that have been added) are highlighted.
6 / Press the “Enter” key on the keyboard when this is done. This will take you back to the previous window.
7 / Click on “OK” to save these changes.
8 / Repeat on the graphs for all levels of controls.
  1. VerifyingValueRanges for Calculations:

Step / Action
1 / Click on the cell that needs the calculation range updated.
2 / Verify that the range of cells selected for the calculation includes the new cells added.
3 / If / Then
  1. The new cells are not included.
  1. The new cells are included.
/
  1. Update the calculation range to include the new cells.
  2. Do not change the calculation formula.

4 / Repeat the above steps for each calculation and for all control levels.
  1. Enter Lot #, Mean, and SD Values: The mean and standard deviations often vary slightly between lot numbers. Enter the values for the mean and SD (+1, +2, and +3 SD) in the small table to the right of the graph.

Step / Action
1 / Enter the lot number for the control in the top of the table to the right of the graph.
2 / Enter the SD values in the corresponding columns in the table to the right of the graph.
3 / As each value is entered, the lines representing the value will automatically appear on the graph.
4 / If / Then
The lines to not automatically appear on the graph. / Check the Y-axis values for the chart (see Change Y-axis values above for instructions).
5 / Repeat for all levels of controls.
  1. Enter Date Information: Entering the date information is done just like entering other information into an Excel spreadsheet. The date will be expressed in two different columns: the first for the day and the second for the month. Be sure that the correct year is also entered above the table for the control information.

Step / Action
1 / Click on the cell where the day of the month will be entered under the “Day” column. The first control should be entered on the row with the Control Number of 1. The following day, information should be entered in the row with Control Number2, etc.
2 / Click on the cell to the right of where the date was entered and type the name of the month when the control was run. This will be directly to the left of the Control Number.
3 / Verify that the correct year has been entered just above this table.
4 / If / Then
The year is incorrect. / Enter the correct year.
  1. Enter Control Values: Every day, after controls have been run, the values for the chemistry controls should be entered into the table. This information will automatically be graphed.

Step / Action
1 / Click on the cell where the control values resulted from the analyzer should go.
2 / Type in the values. Verify that the values have been typed in the correct column (high control values are entered in the Level 3 column, etc.).
3 / Verify that the values have been entered in the correct row: the date and control number match for that sample.
4 / Press “Enter.” The value entered will automatically be graphed.
5 / If / Then
The value isn’t graphed. / Check the Y-axis values for the chart (see Change Y-axis values above for instructions).
  1. Rerunning Controls: When a control value is determined to be unacceptable using established laboratory criteria, the control should be repeated.

Step / Action
1 / Enter each repeated value into the chart. Notice that each repeated value will receive a new control number.
2 / Enter the same date for each repeated run.
3 / Detailed information should be entered into a Corrective Action log if the problem is persistent or warrants documentation.
4 / A note should be entered into the comment field to signify that the control was rerun.
5 / If / Then
Not all levels of controls need to be rerun. / The additional control numbers should be left blank for the other control levels.
  1. Comments: This is a place where abbreviated comments can be entered in regards to a control run. A key with explanations for the comment abbreviations should also be found on the spreadsheet for easy reference. Customize or add comments as needed. The following are some examples.

Step / Action
RR / Result Repeated – Value is a result of control being repeated.
CA / Corrective Action – Corrective action was needed to obtain acceptable control result. Detailed information located in Corrective Action Log.

References: