News from Fitz Scientific

November 2017 - News Stories

November 23rd 2017 10:29

Limit of detection changes

Reporting and Rounding of Final Results

To report a final result correctly the level of accuracy being reported has to be defensible so a laboratory has to identify to what level they are confident in the final result e.g. if we report 10.056grm how confident are we that the 5 hundredths of the gram or 6 thousandths of the gram are accurate enough?

The validation of test processes to ISO 17025:2005 requires that laboratories calculate the amount of uncertainty applicable to the final result of a test to a specific level of statistical confidence. This is a standard process in all good laboratories.

There are a number of methods that can be applied by laboratories to ensure the accuracy of a final result and Fitz scientific are applying guidelines outlined by NIST document GLP 9 (National Institute of Standards and Technology - Good Laboratory Practice for Rounding Expanded Uncertainties and Calibration Values). This ensures that our requirement to meet point 5.10.1 of ISO 17025:2005 (requirement for reporting of results) continues to be met by us while we continue to meet the standard requirement of point 5.9 (assuring the quality of test and calibration results) of the standard.

To be sure that the accuracy of customer results remain a priority we will also round up the LOD to ensure that we can never report below the worst possible case every time. Applying these rules will mean that those validated parameters that have very good uncertainties are reported with more accuracy than a method with a poor uncertainty.

These rules are not applied to intermediate steps and calculations, only to the final result.

This will result in changes to some reports in that LODs will change by being rounded to a specific number of decimal places and also some results may be reported with fewer decimal places than you would have previously seen. This may cause inconvenience for some customers but it is being done with the knowledge and agreement of our ISO 17025:2005 accreditation body and is being done by us to ensure that customers can remain confident in the accuracy of those accredited results that are reported to them in this newer format. None of our test procedures or processes are changing, only the way the final result(s) will be reported to you. We continually work towards improving our test processes to ensure that our customers can maintain the highest levels of confidence in the results we report to them.

If you have any questions in relation to this please contact Damien O'Reilly, Quality Manager 041 9845440.

Source Page: http://www.fitzsci.ie/home/about-us/news/november-2017-news-stories/lod-changes/