Yes Jonathan, the 2006 mailbase exchange was the inspiration for the study below, but we forgot to claim your champagne. I am not sure if you ever did promise
a case. Hic.
Best wishes
Eric
From: Clinical biochemistry discussion list [mailto:[log in to unmask]]
On Behalf Of Shepherd, John
Sent: Thursday, January 07, 2016 1:54 PM
To: [log in to unmask]
Subject: Re: Redefinition of test profiles
Does this count?
Nephron
Clin Pract. 2009;113(3):c203-6. doi: 10.1159/000233057. Epub 2009 Aug 11.
Is there still a role for measuring serum urea in an age of eGFR? Evidence of its use when assessing patient hydration.
Shepherd
J1,
Hatfield S,
Kilpatrick ES.
Abstract
BACKGROUND:
With the current practice of using estimated glomerular filtration rate (eGFR) for the assessment of renal function, serum urea is arguably a redundant test. However, with little evidence,
it is purported that urea can be used as a marker to aid in the assessment of hydration status. The aim of this study was to compare serum urea and eGFR with urine specific gravity (USG) to establish how each compares with this surrogate marker of hydration
status.
METHODS:
The study subjects comprised 2,547 separate acute hospital attendances (1,489 female, 1,058 male; median age (IQR) 60 (39-81) years) where USG and serum urea and creatinine were measured
immediately on admission.
RESULTS:
A significant rise in the median serum urea concentration was observed with increasing categories of USG (p < 0.0001). In contrast, a significant trend was not observed for eGFR vs.
USG (p = 0.65).
CONCLUSION:
Serum urea concentration is significantly affected by hydration status whereas eGFR is not.
From: Clinical biochemistry discussion list [mailto:[log in to unmask]]
On Behalf Of Jonathan Kay
Sent: 07 January 2016 10:38
To: [log in to unmask]
Subject: Re: Redefinition of test profiles
I don’t expect or require anything like STARD. But it has to be more than “I think so” or “I and some other people think so”.
I’m not impressed with the argument from plausibility about the tubular handling of urea at low flow rates.
I am concerned about confirmation bias* from individual clinical experience. And my impression from my teachers and the Tarrytown papers is that plasma urea was originally in there because of the ease of measurement rather
then evidence of diagnostic power. (Note for younger members: high-throughput automated multichannel analysers went into production and routine clinical use before they could be made discretionary by bolting on computers. Strange but true.)
I’ll try and be generous: how about anything above Level 3b? http://www.cebm.net/oxford-centre-evidence-based-medicine-levels-evidence-march-2009/
Happy New Year
Jonathan
* And about loss aversion, but that’s more about reluctance to change practice, rather than the evidence,