Chemistry 6.4 Creatinine, Uric Acid, BUN, and Ammonia

Creatinine is formed from the: A. Oxidation of creatine B. Oxidation of protein C. Deamination of dibasic amino acids D. Metabolism of purines

Creatinine is considered one of the substances of choice to measure endogenous renal clearance because: A. The rate of formation per day is independent of body size B. It is completely filtered by the glomeruli C. Plasma levels are highly dependent upon diet D. Clearance is the same for both men and women

Which statement regarding creatinine is true? A. Serum levels are elevated in early renal disease B. High serum levels result from reduced glomerular filtration C. Serum creatine has the same diagnostic utility as serum creatinine D. Serum creatinine is a more sensitive measure of renal function than creatinine clearance

Which of the following formulas is the correct expression for creatinine clearance? A. Creatinine clearance = U/P × V × 1.73/A B. Creatinine clearance = P/V × U × A/1.73 C. Creatinine clearance = P/V × U × 1.73/A D. Creatinine clearance = U/V × P × 1.73/A

Which of the following conditions is most likely to cause a falsely high creatinine clearance result? A. The patient uses the midstream voiding procedure when collecting his or her urine B. The patient adds tap water to the urine container because he or she forgets to save one of the urine samples C. The patient does not empty his or her bladder at the conclusion of the test D. The patient empties his or her bladder at the start of the test and adds the urine to the collection

The modification of diet in renal disease (MDRD) formula for calculating estimated glomerular filtration rate (eGFR) requires which four parameters? A. Urine creatinine, serum creatinine, height, weight B. Serum creatinine, age, gender, race C. Serum creatinine, height, weight, age D. Urine creatinine, gender, weight, age

What substance may be measured as an alternative to creatinine for evaluating GFR? A. Plasma urea B. Cystatin C C. Uric acid D. Potassium

Which of the following enzymes allows creatinine to be measured by coupling to a peroxidase reaction? A. Glucose-6-phosphate dehydrogenase B. Creatinine deaminase C. Sarcosine oxidase D. Creatine kinase (CK)

Select the primary reagent used in the Jaffe method for creatinine. A. Alkaline copper II sulfate B. Saturated picric acid and sodium hydroxide (NaOH) C. Sodium nitroprusside and phenol D. Phosphotungstic acid

Interference from other reducing substances can be partially eliminated in the Jaffe reaction by: A. Measuring the product at 340 nm B. Measuring the product with an electrode C. Measuring the timed rate of product formation D. Performing a sample blank

Which of the following statements is true? A. Cystatin C is measured immunochemically B. The calibrator used for cystatin C is traceable to the National Bureau of Standards calibrator C. Cystatin C assays have a lower coefficient of variation compared with plasma creatinine D. Enzymatic and rate Jaffe reactions for creatinine give comparable results

In which case would eGFR derived from the plasma creatinine likely give a more accurate measurement of GFR compared with measurement of plasma cystatin C? A. Diabetes B. Chronic renal failure C. After renal transplantation D. Chronic hepatitis

A sample of amniotic fluid collected for fetal lung maturity studies from a woman whose pregnancy was compromised by hemolytic disease of the fetus and newborn (HDFN) has a creatinine level of 88 mg/dL. What is the most likely cause of this result? A. The specimen is contaminated by blood B. Bilirubin has interfered with the measurement of creatinine C. A random error occurred when the absorbance signal was being processed by the analyzer D. The fluid is urine from accidental puncture of the urinary bladder

Which analyte should be reported as a ratio using creatinine concentration as a reference? A. Urinary microalbumin B. Urinary estriol C. Urinary sodium D. Urinary urea

Urea is produced from: A. The catabolism of proteins and amino acids B. Oxidation of purines C. Oxidation of pyrimidines D. The breakdown of complex carbohydrates

Urea concentration is calculated from the BUN by multiplying by a factor of: A. 0.5 B. 2.14 C. 6.45 D. 14

Which of the statements below about serum urea is true? A. The levels are independent of diet B. Urea is not reabsorbed by the renal tubules C. High BUN levels can result from necrotic liver disease D. BUN is elevated in prerenal as well as renal failure

A patient’s BUN is 60 mg/dL and serum creatinine is 3.0 mg/dL. These results suggest: A. Laboratory error measuring BUN B. Renal failure C. Prerenal failure D. Patient was not fasting

Urinary urea measurements may be used for calculation of: A. Glomerular filtration B. Renal blood flow C. Nitrogen balance D. All of these options

BUN is determined electrochemically by coupling the urease reaction to the measurement of: A. H2O2 B. The timed rate of increase in conductivity C. The oxidation of ammonia D. CO2

In the ultraviolet enzymatic method for BUN, the urease reaction is coupled to a second enzymatic reaction using: A. Aspartate aminotransferase (AST) B. Glutamate dehydrogenase (GLD) C. Glutamine synthetase D. Alanine aminotransferase (ALT)

Which product is measured in the coupling step of the urease-UV method for BUN? A. CO2 B. Dinitrophenylhydrazine C. Diphenylcarbazone D. NAD+

Which enzyme deficiency is responsible for phenylketonuria (PKU)? A. Phenylalanine hydroxylase B. Tyrosine transaminase C. p-Hydroxyphenylpyruvic acid oxidase D. Homogentisic acid oxidase

Which of the following conditions is classified as a renal-type aminoaciduria? A. Fanconi syndrome B. Wilson disease C. Hepatitis D. Homocystinuria