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Laboratory Qualification
Two qualification samples were provided. These qualification samples were used to
optimize each participant’s instrument and chromatography. Before proceeding with the
MLT, each participant’s qualification results were sent to and approved by the Study
Director.
After preparation of the stock and working solutions, the performance of the instruments
was determined. The second highest concentration (50 IU/mL) working standard was
injected at least five consecutive times. The relative standard deviation (RSD) of each
compound response for at least five injections must not have been more than 3% for both
forms of the vitamin. After the above criteria were met, the analyst could analyze the
qualification samples. The qualification samples had known amounts of vitamin D
2
and/or vitamin D
3
. After analysis of the qualification samples, the laboratories sent the
qualification result form to the Study Director to review the data. After successful
qualification sample analysis, the data was approved by the Study Director and the
analyst proceeded with the analysis of the test samples.
Data Reporting
Participants were asked to record all observations and any potential method deviations.
In addition, the participants were asked to investigate any potential aberrant results in an
attempt to determine the root cause such as: incorrect calculations, final units incorrect,
transposition errors, incorrect standard preparation or possible contamination. It was also
a requirement to have all the results and calculations reviewed by a peer, laboratory
supervisor or manager.
Data Analysis
The Study Director reviewed and compiled all the data submitted by the participants.
Statistical analysis was conducted using the AOAC spreadsheet for blind duplicates [1].
The following tests were utilized in the AOAC spreadsheet for blind duplicates [1] to
determine outliers: (i) Cochran test
for removal of laboratories showing significantly
greater variability among replicate (within-laboratory) analyses than the other
laboratories for a given material and (ii) Grubbs tests for removal of laboratories with
extreme averages. The spreadsheet was used to calculate the following:
•
mean analyte concentrations
•
standard deviation (S
r
) relative standard deviation (RSD
r
) for repeatability (for
blind duplicate data)
•
standard deviation (S
R
) and relative standard deviation (RSD
R
) for reproducibility
•
number of valid data points
•
HorRat value (RSD
R
/predicted RSD
R
)
2011.11 VITAMIN D MLT-Sept 2015
FOR ERP USE ONLY
DO NOT DISTRIBUTE