Article written by
Jamie Hoban, Quality Control
Supervisor, Analytical Products Group
PT Data Reporting: Ensuring Validity of Submitted Data
Analysis of Proficiency Testing (PT) samples
is vital for maintaining quality assurance and certifications with
regulatory authorities. Sample preparation and examination are
important aspects of participation in a PT program, however these
are not the only considerations in submitting data to the PT
provider. Errors in data reporting can cause a laboratory to receive
an unacceptable evaluation, even if all other portions of the sample
handling were correct. Data reporting is often of particular concern
when dealing with results obtained at low levels with respect to the
PT sample range.
The Data Return Booklet included with all APG PT
samples covers data reporting requirements in section two of the
Performance Evaluation Instructions. These guidelines are consistent
with the US EPA National Standards for Water Proficiency Testing
Studies Criteria Document (December 30, 1998) and are also
summarized in the NELAC PT Data Reporting and Scoring FAQ available
on the internet
[http://www.epa.gov/nelac/archives/ptdatareportingfaqs2.pdf#search='epa%20pt%20data%20reporting'].
Laboratories participating in a PT program should be familiar with
the NELAC PT Tables, also available online
[http://www.epa.gov/nelac/pttables.html]. The PT Tables list
reporting limits for all regulated analytes. These limits are based
on application of regression constants using the lowest possible
assigned value for each analyte. Discrepancies between reporting
limits for regulated analytes and the reporting limits used by
individual laboratories may lead to unacceptable evaluations.
APG, as a PT
provider, is constrained by highly specified regulations
for the evaluation of PT data submitted by
participant laboratories. There are cases where a laboratory may return data
for a PT sample indicating proper preparation and analysis of the sample,
however the submitted data is identified as unacceptable due to non-compliance with
the reporting guidelines. For this reason, data reporting requirements must
be understood and as carefully reviewed as the preparation techniques
and analysis methods used.
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