Dear Rita,
We have heard this before. "In the world of imperfect solutions...." we tell lies like the eGFR, we know that the calculated quantity is not the individual's GFR, we know that the adjusted Ca concentration is not the Ca concentration of the serum/plasma.
It would be fair to use the measured quantities and teach the caveats, moreover I believe the estimated, calculated, adjusted values give a false impression of accuracy to the clinician or other user.
This takes us to the uncertainty issue, which has been given more weight in the revision of the EN/ISO 15189 - good or bad. I believe it is a misconception that the uncertainty interval should be attached to the report. I would rather see the minimal difference (MD) reported, that is what concerns the clinician, not the measurement uncertainty (MU) which I believe should be regarded as a management tool for the laboratory, carefully supervised by the IQC.
Graham's sheets are of course incomprehensible. The MD or reference change value (RCV, including some preanlytical variation) can be expressed as a range and thus summarized as one number linked to the name of the quantity. This wuld be a delta-check without computer! There is an abundance of good literature on this e.g. by Callum Fraser, Jim Westgard. Per Hyltoft-Petersen and Carmen Ricos.
But stop manipulating measured values by population algorithms!
Ionized calcium activity - by the way - is not as difficult to measure accurately as the rumor may indicate (Kallner Eur J Clin Chem Clin Biochem 1996; 34:53-58 Preanalytical Procedures in the Measurement of Ionized Calcium in Serum and Plasma) and the techniques have developed considerably since then. I have been told it takes an average of 17 years for a new technique to be accepted in medicine! Thus, it is about time!
Enjoy mid-summer (winter)!
Anders Kallner
-----Original Message-----
From: Rita Horvath [mailto:[log in to unmask]]
Sent: den 19 juni 2013 00:02
To: Anders Kallner; [log in to unmask]
Subject: RE: Population based algorithms
Anders, what we in fact do is that we offer adjCa 8using our in-house validated equation) to a restricted group of patients and in a restricted albumin conc range only. We have informed our dr-s about the estimated nature of the calculation (which is only a very rough guide at best) and the need for proper ionized Ca measurement if clinically deemed necessary. This is all commented on lab resports too as a constant reminder. I think in the world of imperfect solutions the best we can do is to inform them clearly and be transparent about the uncertainties associated with our reported results. Just letting them do with results what they think might be right is not appropriate laboratory service, in my view, and in fact can cause harm to some patients.
Having said this, I have just recently lectured GPs on inappropriate laboratory testing and when I highlighted to them the concept of measurement uncertainty, biol. var, etc, they became very keen on us reporting results with the uncertainty estimate so that they can take that into account when interpreting lab data. The only anecdote I remember about such an approach is that one Australian lab tried this at least a good decade ago but nearly went out of business as dr-s did not like to see plus/minus figures and felt the lab was not good enough to give them the 'right' result...so they had to stop this practice...I often ask why do we bother then having big spreadsheets of uncertainty calculations if we rarely use this for clinical information - just to plse the accrediting body??? Wonder how many labs report results with uncertainty estimates (!!!NB: estimates)?
So this simple question on Ca leads us to a lot of conceptual issues we still failed to solve as a profession, I am afraid.
Kind regards, Rita
________________________________
From: Clinical biochemistry discussion list [[log in to unmask]] On Behalf Of Anders Kallner [[log in to unmask]]
Sent: Tuesday, 18 June 2013 11:07 PM
To: [log in to unmask]
Subject: Population based algorithms
Dear Rita
A pertinent question may be if laboratories shall calculate, correctly, what we know is wrong or leave it to the clinicians to wrongly calculate what is wrong anyway. It is not always that two negatives cancel.
Best regards,
Anders
Anders Kallner, MD, PhD
Assoc. Professor (R)
Karolinska Univ. Laboratories
Stockholm SWEDEN
+46 8 51774943
[log in to unmask]<mailto:[log in to unmask]>
------ACB discussion List Information-------- This is an open discussion list for the academic and clinical community working in clinical biochemistry. Please note, archived messages are public and can be viewed via the internet. Views expressed are those of the individual and they are responsible for all message content. ACB Web Site http://www.acb.org.uk Green Laboratories Work http://www.laboratorymedicine.nhs.uk List Archives http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html List Instructions (How to leave etc.) http://www.jiscmail.ac.uk/
---------------------------------------------------------------------------------------------
Illawarra Shoalhaven Local Health District, South East Sydney Local Health District and Sydney Children's Hospital Network (Randwick Campus) Confidentiality Notice
This email, and the files transmitted with it, are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you are not the intended recipient, you are not permitted to distribute or use this email or any of its attachments in any way. We also request that you advise the sender of the incorrect addressing.
This email message has been virus-scanned. Although no computer viruses were detected, Illawarra Shoalhaven Local Health District, South East Sydney Local Health District and Sydney Children's Hospital Network (Randwick Campus) accept no liability for any consequential damage resulting from email containing any computer viruses.
------ACB discussion List Information--------
This is an open discussion list for the academic and clinical community working in clinical biochemistry.
Please note, archived messages are public and can be viewed via the internet. Views expressed are those of the individual and they are responsible for all message content.
ACB Web Site
http://www.acb.org.uk
Green Laboratories Work
http://www.laboratorymedicine.nhs.uk
List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
List Instructions (How to leave etc.)
http://www.jiscmail.ac.uk/
|