The use of the beckman BUN analyser to determine the urea concentration in whole blood

The use of the beckman BUN analyser to determine the urea concentration in whole blood

Clin. Biochem. 14 (2) 102-103 (1981) LABORATORY NOTE The Use of The Beckman BUN Analyser to Determine the Urea Concentration in Whole Blood HANS M.C...

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Clin. Biochem. 14 (2) 102-103 (1981)

LABORATORY NOTE

The Use of The Beckman BUN Analyser to Determine the Urea Concentration in Whole Blood HANS M.C. H E I C K I, A Z I Z MOHAMMED a n d NICOLE BI~GIN-HEICK

The Eleanor M. Paterson Department of Laboratory Medicine and Research Children's Hospital of Eastern Ontario, 401 Smyth Road, Ottawa, Ontario K1H 8L1 and Department of Biochemistry, University of Ottawa, Ottawa, Canada THE BECKMANBUN* ANALYSER measures the rate of change of conductivity when urea is hydrolysed by urease (1). It is developed for use with serum and plasma samples, but recently we have shown that the i n s t r u m e n t will also measure urea in urine (2). We report that it can also be used on whole blood samples.

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METHODS

The Beckman B U N Analyser, Model 6156 was purchased from Beckman Instruments, Fullerton, Ca. The reagent was made in-house as described previously (2). The samples were all human blood samples collected with lithium heparin. For comparison of whole blood and plasma, the samples were divided. One aliquot was used for the whole blood determination and the other was centrifuged to provide the plasma sample. RESULTS AND DISCUSSION

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The precision of the method was tested by measuring the within-day coefficient of variation at three different levels. The results are shown in Table 1. Sample No. 1 was within the reference range and gave a coefficient of variation of less than 30/0. With the higher values found in uremic patients, the coefficient of variation was less than 2%. We reported similar figures for urine values (2). The correlation between values obtained with the blood and plasma samples was investigated by measurTABLE 1. PRECISIONOFWHOLEBLOODUREANITROGENDETERMINATIONS PERFORMEDONh BECKMANBUN ANALYSERMODEL6156 Sample

Number of Samples

Mean Value (mg/dl)

Coefficient of variation

1 2 3

15 15 15

15.7 55 73

2.9% 1.8% 1.8%

1Children's Hospital of Eastern Ontario, Biochemistry Division, 401 Smyth Rd., Ottawa, Canada K1H 8L1 *Editor's note: Although this instrument is called a B U N (Blood Urea Nitrogen) Analyzer, it is not claimed by the manufacturer that it can be used for whole blood. A more appropriate name might be "Urea Analyser".

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Fig. 1 -- Correlation b e t w e e n urea n i t r o g e n in p l a s m a and w h o l e blood, as d e t e r m i n e d on a B e c k m a n B U N A n a l y z e r , M o d e l 6156.

ing urea nitrogen in whole blood and plasma from 117 patients. The plasma values varied from 1 mg/dl to 186 mg/dl, and the regression line equation from these results was as f o l l o w s ; Y = 0.97X + 1.36, where Y r e p r e s e n t s the whole blood values and X the plasma values. A correlation of 99% was obtained. The results of the individual samples are displayed in Fig. 1. There was good a g r e e m e n t between the two samples throughout the range examined. There are advantages in being able to use whole blood instead of serum or plasma for chemical determinations: time is not lost in separating the sample and the total amount of blood required may be smaller. i , - : t r u m e n t s now exist for measuring blood gases (e.g., Radiometer ABL, The London Co., Cleveland, Ohio), electrolytes, (e.g., Nova 4, Nova Biomedical, Newton, MA), and glucose (YSI23A glucose analyser, Yellow Springs I n s t r u m e n t Co., Yellow Springs, Ohio) on whole blood. These determinations, along with urea,

BECKMAN BUN ANALYSER TO DETERMINE THE UREA CONCENTRATION IN WHOLE BLOOD comprise the bulk of emergency requests. The work reported here indicates that the Beckman BUN A n a l y s e r can be used to measure urea in whole blood, making possible emergency t e s t i n g primarily with whole blood. The method is also useful when the a m o u n t of sample is limited, as in a pediatric service or for research work involving small animals.

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REFERENCES 1. Horak, E., and Sunderman, F.W., Jr. Measurements of serum urea and nitrogen by conductivimetric urease assay. Ann. Clin. Lab. Sci~ 2, 425-431 (1972).

2. Heick, H.M.C., Mohammed, A., and Bdgin-Heick, N. Use of Beckman B U N Analysers to Determine Urine Urea. Clin. Biochem. 12, 104-106 (1979).