----- Original Message -----
From: "Graham Jones" <[log in to unmask]>
Subject: Bilirubin and creatinine assays
> Does anyone have experience with the effect of conjugated bilirubin on
> Jaffe or enzymatic methods? Does anyone have a source for conjugated
> bilirubin for in-vitro studies?
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Conjugated bilirubin is costly and difficult to exactly weigh. Therefore I
use to perform a "reverse" method to evaluate the interference of bilirubin
on creatinin methods. I add creatinin to patient samples with naturally
elevated bilirubin instead of adding bilirubin to samples with naturally
elevated creatinin.
1) Prepare a solution of about 2 g/l creatinin in water
2) Search for 2 patient samples among the daily tubes of the laboratory :
LB : with very low bilirubin < 5 mg/l
HB : with very high bilirubin > 200 mg/l
3) Prepare four secondary tubes
LB1 : 500 ul LB sample + 25 ul creatinin 2 g/l
LB2 : 500 ul LB sample + 25 ul water
HB1 : 500 ul HB sample + 25 ul creatinin 2 g/l
HB2 : 500 ul HB sample + 25 ul water
4) The four tubes are assayed for bilirubin and creatinin
5) The interference of bilirubin on creatinin is calculated as the recovery
ratio :
RR = (Creat HB1 - Creat HB2)/(Creat LB1- Creat LB2).
With this method, there is no significant interference of bilirubin (RR # 1)
with our current Jaffe Olympus reagent (OSR6178) up to at least 300 mg/l.
Philippe Marquis, MD
Service de biochimie
Centre hospitalier régional
Metz - France
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