Dear James and all,
My view, and what we do in our hospital, is that it could be wrong to
report an ionised calcium corrected to pH 7.4 on a blood gas sample
(anaerobic, rapid measurement). We know the actual iCa and the actual pH
so just report these. We have removed this parameter from the printout
and reporting screen for all our blood gas machines located near
patients.
I have no information to support a different reference interval for iCa
from patients with pH's significantly different from 7.4 and therefore
use our usual reference interval. I would welcome further comments on
this.
Graham
Graham Jones
Staff Specialist in Chemical Pathology
St Vincent's Hospital, Sydney
Ph: (02) 8382-9160
Fax: (02) 8382-2489
>>> James J Miller <[log in to unmask]> 08/12/05 9:59 PM >>>
Analogous to John Whitfield's question about Blood Gases and Temperature
Corrections, I've wondered about the appropriateness of correcting iCa
to pH 7.4. The main reason for this is to control for changes in pH
after sample collection, but many of our patients are acid-, or
alkalemic. It seems like a correction to the patient's pH instead of or
in addition to correction to pH 7.4 would be more clinically relevant.
Most of the time we do not know the patient's pH at the time of
collection of the iCa sample, but some blood gas analyzers also have
iCa. Do those analyzers include a correction to the patient's pH? I'd
be interested in your thoughts about this issue. -Jim
James J Miller, Ph.D., DABCC, FACB
Associate Professor, Pathology & Laboratory Medicine
University of Louisville, Louisville, KY 40292
Director of Clinical Chemistry & Toxicology
University of Louisville Hospital Laboratory
[log in to unmask]
Office: 502-852-1179
Pager: 502-478-1219
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