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LGC Maine Standards Data Reduction Report Explained 

Peer Group Analysis


Participating in LGC Maine Standards' Peer Group Analysis: 

In order to be included in and receive Peer Group Analysis from LGC Maine Standards, you must complete the Peer Group Set-Up Packet.  This packet will provide us with the necessary method information required to ensure that your results are included in, and are compared to, the proper peers.  Linearity and Peer Group analysis is provided free of charge with the purchase of any VALIDATE® linearity and calibration verification material.

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Peer statistics table: 

Displays the statistical information for your peer group.  Statistics provided are the peer mean, the number of labs in your peer group, the number of data sets included in the peer, the Standard Deviation of the peer mean and the % Coefficient of Variation (% CV) of the peer mean.

The number of labs in your peer group and the number of data sets may vary per level depending upon the results reported by level from each customer.

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Percent difference versus peer mean graph: 

Displays your mean recovered values as compared to peer means at each linear dilution level.  Your mean results are plotted as a percent difference from the peer means.  

The red lines on the graph represent the allowable error for each level.  

The yellow lines represent two times the percent Coefficient of Variation for each level.

This display makes it easy to visually see your deviation versus peer means.

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Peer comparison table: 

Displays your mean values for each linear dilution level as compared to the peer means.  ‘+/- Diff’ is the absolute difference between your mean value and the Peer Mean.  ‘% Diff’ is the percent difference between your mean value and the Peer Mean for each ‘Effective X’ value.

An evaluation of the deviation from the peer mean is also provided.  The ‘+/- Limit’ and the ‘% Limit’ are the allowable absolute and percent limits, respectively, around your mean values.

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Applied limits: 

Fifty percent of the total allowable error, as defined by CLIA (42 CFR 493) and/or other published industry accepted standards, is used in Peer Analysis.

The ‘+/- Diff’ and ‘% Diff’ are compared to the allowable limits at each Effective X value to determine acceptability of your results as compared to your peers.  Most allowable error limits are an absolute value and a percentage, whichever is greater.  If the difference is greater than the limits set, the difference will be bolded with a ‘**’ flag.

In the case of the GLU shown here, the allowable error limit is 3.00 mg/dL or 5%, whichever is greater.  For Effective X values 2.0 through 5.0, 5% of the target value is greater than 3.00 mg/dL, so a limit 5% is applied.  When the percent limit is applied, the ‘+/- Limit’ column will display the calculated absolute limit around your mean.

In the GLU example, the absolute limit of 3.00 mg/dL is applied to Effective X 1.0; the ‘+/- Diff’ is less than 3.00 mg/dL.  For X values 2.0 through 5.0, the 5% limit is applied and the pass/fail indication is displayed in the ‘% Diff’ column.  In this case, all results are within allowable limits, so none of the actual differences are flagged.

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Insufficient Data for Peer Analysis: 

In some cases there may be insufficient data available to provide Peer Group statistics for a particular analyte.  This can occur if the peer data does not pass a statistical check, or if there are fewer than 10 labs reporting data for a particular analyte/method.  The statement “No Peer Data Available” will be displayed over the Peer Statistics and Peer Comparison Tables and no % Difference plot will be displayed.

However, if any peer data is available, you will receive a report detailing the Peer Minimum, Peer Median and Peer Maximum for each linear dilution level as well as a comparison of your mean to the Peer Median.  In this instance, no % Difference plot will be displayed.

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Additional Information: 

For information on the calculations used in LGC Maine Standards Data Reduction Linearity and Peer Group Analysis, please see this Data Reduction Method Explained.

For information on Total Allowable Error Limits please see:

CLIA Section 493.931 Regulation (Chemistry)
CLIA Section 493.937 Regulation (Toxicology)

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Data Submission Form

Target Calculation Worksheet


Free Data Reduction Software Download: