Dear Wolfgang Schneider and other colleagues,
In our lab we also use the benzethonium chloride Hitachi 917 method for
urinary protein analysis. Recently we encountered the same problem as you
describe: high urinary protein on the Hitachi with negative/low dipstick
results. Dilution of the urine on the Hitachi gave non-linear results.
The reason for this discrepancy appeared to be the use of Gelofusine (a
plasma-expander) for this patient. This has been described recently in
Scand. J. Clin. Lab. Invest. 1999; 59; 133-138 "Infusion of plasma expanders
may lead to unexpected results in urinary protein assays" by M.H. de Keijzer
et al.
Gelofusine appears to interfere with the urinary protein analysis in a
number of different methods. A quick control might be to measure
micro-albumine in urine on the Hitachi; this should not be (falsely)
elevated.
Perhaps this may solve your problem.
Kind regards,
Marjolein van Kleffens
----------------------------------------------
Dr. M. van Kleffens
Asp Clin. chem.
KCHL, St. Maartens Gasthuis
POBox 1926
5900 BX Venlo
The Netherlands
tel +31.77-3205251
fax +31.77-3205216
e-mail [log in to unmask]
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-----Oorspronkelijk bericht-----
Van: [log in to unmask] <[log in to unmask]>
Aan: [log in to unmask] <[log in to unmask]>
Datum: woensdag 20 oktober 1999 11:31
Onderwerp: Interference in urine proteine assay ?
>
>
>
>Dear colleagues,
>
>We have been using the Roche benzethonium chloride method for urinary
protein on
>a Hitachi 917 (run as a rate assay) successfully for quite a while but
recently
>ran into a problem.
>
>We measured 1.97 g/L of protein on a patient who also happened to have a
request
>for urine protein electrophoresis. The sample was concentrated 50fold but
gave a
>faint protein pattern not compatible with the expected protein
concentration. A
>subsequent dipstick reading was 0.3 g/L. Diluting the sample two and
fourfold
>gave 1/2 and 1/4 of the original concentration by benzethonium, as
expected. We
>then sent the sample to two other labs and got 0.2 g/L with the
sulfosalicylic
>acid method and 0.58 g/L with the pyrogallol method.
>
>Interestingly, the patient had shown a discrepancy between the benzethonium
and
>the dipstick method four weeks earlier already (1.45 g/L vs 0.3 g/L) but
had
>much more compatible results ( 0.08 g/L vs negative protein) five weeks
earlier.
>
>The only interference listed for the assay is hemoglobin at > 50 mg/dL but
the
>urine was yellow and the dipstick was negative for blood. When I called
Roche
>they had no other information on interferences on file.
>
>The patient was on antibiotics, though, some of which interfere in other
urine
>protein assays. He was using Azithromycin, Trimethoprim and
Sulfamethoxazole. He
>was also on Colchicine, Sucralfate, Docusate, and Prednisone, unlikely
>candidates for interference. He's off his antibiotics now and expected back
soon
>for another urine sample.
>
>Has anyone else seen interference in this assay ?
>Many thanks
>
>***********************************************************
>Wolfgang Schneider
>Division of Medical Biochemistry, Montreal General Hospital
>1650 Cedar Avenue, Montreal, Quebec H3G 1A4, Canada
>Phone (514)-937-6011 x 2782 Fax (514) 934-8086
>Email at work: [log in to unmask]
>Email at home: [log in to unmask]
>Manufactured only with 100% recyclable electrons
>***********************************************************
>
>
>
>
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