Regarding haemolysed samples from the Emergency Department:
As with the previous discussants we note a high frequency of haemolysed
samples form the Emergency Department (4-5%) compared with the general
wards (<<1%). This is detecting haemolsyis using the Hitachi indices at a
level of "100".
I congratulate the other discussants in being able to trace the exact cause
(collection through and iv infusion canula) as we have strongly suspected
this but have been unable to get ED doctors to admit this in any particular
case.
This has been investigated in a number of papers:
Kennedy et al. Journal of Emergency Nursing. 1996;22:566-9
Raisky F et al. Annales de Biologie Clinique 1994;52:523-7
Both these papers support your findings of higher haemolysis rates with
collection through iv canulas (I confess to only seeing the abstracts).
Our response (being unable to get the Ed doctors to change their practice)
is to provide a "corrected" total CK and potassium for the amount of
haemolysis ( following the work of Jay and Pravasek, Clin Chem
1993;39:1804-10). This suppoted by local experiments showing sufficiently
constant inter-personal ratios of red cell haemoglobin:potassium and
haemoglobin:CK. As well we have vaildated the algorithms using haemolysed
and non-haemolysed samples from the same patients in the ED. While this is
an approximate correction only, we believe it is better than the delay (and
annoyance) caused by asking for a recollection in each of these cases.
CK-MB we found was not affected by haemolysis up to an H of "1000".
Graham Jones
Staff Specialist in Chemical Pathology
St Vincent's Hospital, Sydney
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