Jonathan,
You seem to have rehersed the various camps points fairly well
each group can quote "horror" stories of misinterpretation. Presumably
good practice dictates reporting the result with the Reference Interval
to aid interpretation?
Moles would be so much more useful if only there were:-
a. Proteins reported in moles too!
b. Metabolites were measured [and sometimes they should be]
c. There was GOOD evidence of effect/ concentration
relationships for most measured drugs
d. The end users understood the inherent temporal relationships
of pharmacokinetics!
Ian D Watson
[log in to unmask]
Dept Biochemistry
University Hospital Aintree
LIVERPOOL L9 7AL
In message <[log in to unmask]>, Jonathan Kay
<[log in to unmask]> writes
>>>We have recently joined 3 laboratories together in a partnership, but we
>>>have a problem with units for reporting drugs - both TDM and toxicology.
>>>We are reporting molar units in one lab and mass units in the other two,
>>>and this has caused a potentially dangerous situation in swapping
>>>specimens between laboratories.
>
>I have tried to get some action on this from professional bodies as there are
>significant quality and educational issues involved. So far I haven't made
>any progress. In the meantime here are some well-rehearsed and conflicting
>ideas that crop up early in the numerous debates I've heard.
>
>1 We should immediately abandon decilitres and only use litres in the
>denominator. This will remove one source of confusion.
>
>2 We should use gravimetric units as that's how drugs are prescribed.
>(Presumably from people who think that numerical compartmental analysis is
>widely used by prescribers.)
>
>3 Prescribers hould switch to using molar units in prescriptions in order to
>get the right number of molecules of the active substance into the patient.
>(Then it wouldn't matter which salt etc is used in the formulation. See also
>the wonderful story of the "expert recommendations" in the WHO guidelines for
>GTTs and the confusion of glucose and glucose monohydrate, possibly in Keith
>Weiner's editorial in the BMJ...)
>
>4 We should use the SI principle of molar units for substances for which we
>know the molecular mass.
>
>5 "Molar thinking" improves "chemical pathology thinking"...calculating anion
>gaps, why you can omit the concentration of hydrogen ion when calculating
>anion gaps (!), explaining "corrected calcium"...
>
>6 For ethanol everyone uses "multiples of the legal limit for driving" when
>interpreting reports anyway.
>
>7 Responders to EQAS often make mistakes with the units for assays of
>exogenous substances. But that is an artificial situation which may not
>represent their own clinical practice.
>
>8 Junior doctors are pretty mobile so local agreements don't solve all the
>problems.
>
>9 Much of the interpretation is done in relation to literature values so
>local agreements don't solve all the problems.
>
>My own view:
>
>mol/L, and the sooner the better.
>
>Jonathan Kay
>
>
--
Dr Ian D Watson
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