[2S] UNIT 9.1 Urea

Nitrogen-containing compounds measured after removal of proteins in specimen

Measured by converting nitrogen to ammonia and subsequent reaction with Nessler’s reagent (K2[Hgl4]) to form a yellow product measured spectrophotometrically

NPNs specimen

URINE OR PLASMA Assesses the kidney

URINE OR PLASMA For urea concentration test

Also known as carbamide

Most abundant NPN (50%)

Produced in the liver from amino groups (-NH2) and free ammonia

Major excretory product of protein metabolism

Chemical formula of Urea

CLINICAL APPLICATIONS Evaluation of renal function

CLINICAL APPLICATIONS Assess hydration status

CLINICAL APPLICATIONS Determination of nitrogen balance

CLINICAL APPLICATIONS Aid in the diagnosis of renal disease

More appropriate term for quantification of urea

CLINICAL APPLICATIONS Verify adequacy of dialysis

T/F: DIALYSIS - ↑ BUN = dialysis isn’t compensating

Conversion factor of BUN (mg/dL to mmol/L)

BUN DETERMINATION Most frequently used method

BUN DETERMINATION Uses urease enzyme to catalyze hydrolysis of urea and the liberated ammonium ion (NH4 +) is quantified.

BUN DETERMINATION Most common assay

BUN DETERMINATION Best as a kinetic measurement

BUN DETERMINATION Measures rate of disappearance of nicotinamide adenine dinucleotide (NADH) at 340 nm

BUN DETERMINATION Used in automated systems, multilayer film reagents and dry reagent strips