We are getting new equipments (Vitros, Ortho-Clinical Diagnosis) which
measures LDH activity in the pyruvate to lactate direction which is
driven at 37C, therefore giving a completely different reportable and
reference range from our present method which is driven in the L to P
direction. This introduces a potential problem because MDs get "used to"
a certain reference range and apart from using the test to detect "high"
or "low" levels, they utilize the numeric results to correlate with
clinical observations (eg LDH level and degree of hemolysis). Some other
users of our new method implement factoring / scaling so that they can
continue to report in the "usual" range that most MDs understand, but
this has been criticized because the factoring continues after the old
method has long been discontinued and therefore there is no way to
verify the correlation. My questions are:
1) Is it justifiable to do such a factoring exercise to satisfy the
clinicians?
2) If such a factoring procedure valid? - even though this is the same
reaction only driven in opposite directions, they are still two
different reactions with their own kinetics and specific reagents etc so
I guess it would be like correlating "LDH level" with "degree of
hemolysis" which are two independent events with an association.
I guess someone may have brought these issues up before, but please bear
with a newcomer like myself. Many thanks.
Dr K Chan, MD.
Department of Laboratory Medicine,
Belleville General Hospital,
Belleville, Ontario, Canada
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