Julian Barth will surely answer this thread as they have just recently published a paper on this topic in children in the Annals. (Ann Clin Biochem 2012; 49: 352-358.)
However, there are some other papers that I am happy to share with you. If you use a formula you should truly validate it to your method as the textbook one traditionally quoted and also referred to in one of the responses is no good for e.g. BCP albumin. We also use such an internally validated formula in our lab and we only report adjusted Ca if the albumin is >30 and <50 g/L, which is probably a cautious approach. We provide ionized Ca on our POCT blood gas analysers at various critical wards.
I quote here a paper about validation of these formulas as well as some papers from clinical and lab professionals (attached) who question the validity of any adjusted Ca measurements.
The impact of the assay for measuring albumin on corrected ('adjusted') calcium concentrations
Laura Labriola, Pierre Wallemacq, B´eatrice Gulbis and Michel Jadoul
Nephrol Dial Transplant (2009) 1 of 5 doi: 10.1093/ndt/gfn747
Derivation and internal validation of an equation for albumin-adjusted calcium
Matthew T James, Jianguo Zhang, Andrew W Lyon and Brenda R Hemmelgarn
BMC Clinical Pathology 2008, 8:12 doi:10.1186/1472-6890-8-12
This article is available from: http://www.biomedcentral.com/1472-6890/8/12
Kind regards, Rita
Prof. Andrea Rita Horvath, MD, PhD, EurClinChem, FRCPath, FRCPA
Past President of the European Federation of Clinical Chemistry and Laboratory Medicine
Clinical Director, SEALS North, Department of Clinical Chemistry
Level 4, Campus Centre, Prince of Wales Hospital
Barker Street, Randwick, NSW 2031, Sydney, Australia
Tel: (+612)-9382 9078
Fax: (+612)-9382 9099
Mobile No: (+61)-404 027 843
From: Clinical biochemistry discussion list [mailto:[log in to unmask]] On Behalf Of Mainwaring-Burton Richard (SOUTH LONDON HEALTHCARE NHS TRUST)
Sent: Friday, 23 November 2012 1:46 AM
To: [log in to unmask]
Subject: Re: Ionised calcium in ICU
Having donated all my copies of the Annals 1978 to 2000 to the ACB office as part of an office-clearance/pre-retirement-fit-of-benevolence, I am unable to access :
......Julian Barth's method of calculation (Ann Clin Biochem 1996; 33: 55-58) which uses lots of your own lab patient data to plot total calcium vs.albumin over the albumin range 20-55g/L, excluding patients with abnormal urea/creatinine/AST/alk phos/potassium. You end up with a pretty linear graph whose regression line is your adjustment formula.
Cited on the mailbase in October 2000
Can anyone please oblige with a scanned or .pdf version ?
with best wishes
Richard
Richard Mainwaring-Burton
Consultant Biochemist
South London Healthcare Trust
Queen Elizabeth Hospital, Woolwich
Princess Royal Hospital, Farnborough
Queen Mary's Hospital, Sidcup
020-8836-5724
mob: 07831-739876
From: Clinical biochemistry discussion list [mailto:[log in to unmask]] On Behalf Of Jonathan Kay
Sent: 22 November 2012 12:33
To: [log in to unmask]
Subject: Re: Ionised calcium in ICU
What algorithm do you use to calculate "adjusted calcium"?
What method do you use to measure albumin?
How well do those two work together?
Jonathan
On 22 Nov 2012, at 12:29, Mohammad Al-Jubouri wrote:
Dear All,
We only measure total calcium reported as adjusted calcium on ICU patients and a significant number have low results. An ICU calcium replacement protocol is instigated, however the calcium result remains low. Now ICU wants ionised calcium added to their blood gas machine for monitoring calcium status of their patients.
Any words of wisdom on the clinical usefulness of inoised calcium in this setting is welcome.
Many thanks
Mohammad
Dr. M A Al-Jubouri, MB ChB, MSc, FRCP Edin, FRCPath
Consultant Chemical Pathologist
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