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Creatinine Standardization Recommendations
Proficiency Testing and External Quality Assessment (PT/EQA) providers
will be crucial partners in the successful implementation of the
Creatinine Standardization Program. For PT/EQA providers, the following
steps are necessary:
Advise participant laboratories that you will collaborate with
in vitro diagnostic (IVD) manufacturers, the European Communities
Confederation of Clinical Chemistry (EC4), the International Federation
of Clinical Chemistry and Laboratory Medicine (IFCC), and NKDEP to
ensure appropriate grading of PT/EQA data during a transition period
for implementation. Make necessary changes in participant grading within your
respective survey programs during the transition of routine creatinine
methods to revised calibrations that are traceable to an isotope
dilution mass spectrometry (IDMS) reference method.
It is anticipated that bimodal
distributions of survey results within a method may be observed. When
this occurs, it will most likely be the result of groups of
laboratories independently transitioning to new creatinine calibrations
for a particular method. This should not be a cause for a given
laboratory to fail a PT/EQA challenge. Thus, it may be necessary for
PT/EQA providers to collaborate with IVD manufacturers to create new
instrument/method peer groups (traditional or IDMS-traceable
calibration) for their participants that reflect the calibration status
of each method that is undergoing a calibration transition for both
serum and urine creatinine values.
Inform participant laboratories that they will need to choose
the correct instrument/method peer group (subclassified as traditional
or IDMS-traceable calibration) for the creatinine calibration in use by
their laboratory for a given PT/EQA challenge. Request IVD manufacturers’ expected dates for
introduction of IDMS-traceable calibrations for creatinine for each of
their methods, and the anticipated timeframe to achieve completion of
the transition for a given method to the new calibration in all routine
clinical laboratories using that method around the world.
Over the longer term, NKDEP recommends
introducing a regularly recurring PT/EQA program that uses commutable
serum materials with target values traceable to the IDMS reference
method for creatinine. Such a program will allow individual
laboratories and IVD manufacturers, on an on going basis, to assess the
performance of routine clinical laboratory methods and the success of
the calibration-adjustment process for each of their methods. However,
IDMS target values should not be assigned to PT/EQA materials, nor
should they be used to evaluate participant performance, unless the
materials have been validated to be commutable with native clinical
samples for the routine methods being evaluated.
For additional information about commutable
serum reference materials and their application to PT/EQA programs,
refer to: Miller WG, et al. Creatinine measurement: state of the art in accuracy and interlaboratory harmonization. Archives of Pathology and Laboratory Medicine, 2005;129(3):297–304; and Miller WG, Myers GL, Rej R. Why commutability matters. Clinical Chemistry 2006;52:553-4.
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