85 Questions
What is the primary role of urea in the body?
To remove waste products from the circulation
What is the term used to describe urea in the context of protein metabolism?
Urea nitrogen
Where is urea synthesized in the body?
Liver
What is the purpose of measuring urea levels in clinical chemistry?
To evaluate renal function
What is the source of urea in the body?
Deamination of amino acids
What is the conversion factor to convert BUN to urea?
2.14
What does increased serum urea indicate?
Renal failure, glomerulonephritis, or urinary tract obstruction
What is a possible reason for decreased serum urea?
Severe liver disease
What type of disorders can cause abnormal serum urea levels?
Prerenal, renal, or postrenal disorders
Why is the term 'blood urea nitrogen' still used?
Because it was based on previous methodology where nitrogen was measured
What can the levels of urea indicate?
The stage of a kidney disorder
What is a possible cause of increased serum urea?
Congestive heart failure
What is another purpose of measuring urea levels?
To assess the patient's hydration state
What is a possible reason for decreased serum urea?
Severe liver disease
What is the significance of urea measurement in dialysis patients?
To assess the adequacy of dialysis
What is the expected outcome of proper dialysis on urea levels?
A slight decrease to levels slightly higher than normal
What is the basis of urea measurement in the blood sample?
Measurement of nitrogen levels
What is the target range for creatinine levels after dialysis?
Slightly higher than normal
What is the sample type used for urea measurement?
Protein-free filtrate of whole blood
How many analytic methods are employed in the lab to determine urea levels?
At least two
What is the product formed when urea reacts with glutamine dehydrogenase?
Glutamate + NADH + hydrogen
What is the reference range for urea levels in the blood?
6 to 20 milligrams per dL
What is the outcome of the reaction between diacetyl monoxime and water?
Formation of hydroxylamine and diacetyl
What is the final product formed in the Chemical Method of urea measurement?
Yellow diazine derivative
What is the enzyme involved in the Kinetic Method of urea measurement?
Glutamine dehydrogenase
What is the function of urease in analytical methods?
To catalyze the hydrolysis of urea
What specimen is susceptible to bacterial decomposition and should be refrigerated if not tested immediately?
Urine
What is the significance of fasting in urea testing?
Fasting has a negligible effect on urea levels
What is Azotemia?
An elevated concentration of urea in the blood
What is the basis of urea measurement in the GDH method?
The rate of disappearance of nicotinamide adenine dinucleotide
What is the name of the enzyme involved in the enzymatic method of urea measurement?
Urease
What is uremic syndrome also known as?
Urea syndrome
What is the result of reduced renal blood flow during instances like congestive heart failure?
Reduced blood flow to the kidney
What is the consequence of less blood being filtered by the kidney?
More urea in the circulation
What is a possible cause of prerenal disorders?
Congestive heart failure
What is characterized by slight increases in urea levels?
Prerenal stage
What can lead to uremic syndrome if left untreated?
Renal problems and renal failures
What is the primary cause of increased plasma urea concentration in the renal stage?
Compromised urea excretion
What is the term used to describe the obstruction of the urinary tract?
Postrenal Stage
Why does the kidney become dysfunctional in chronic renal disease?
Due to the damage to the kidney's filtering ability
What can aid in the differentiation of the cause of abnormal urea concentration?
Calculating the urea nitrogen to creatinine ratio
What is the outcome of proper management of patients with abnormal urea concentrations?
Improved patient outcomes
What is creatinine formed from in the body?
Phosphocreatine
What is the primary function of measuring creatinine levels?
To determine the severity of kidney damage
Why are creatinine levels regulated by kidney excretion?
To monitor kidney function
What is the relationship between creatinine levels and blood urea nitrogen (BUN)?
They are directly proportional
What happens if creatinine levels continue to rise after medication?
The medication is not effective
What is the significance of differences in muscle mass of the sexes?
It affects creatinine levels
What is the reactant that reacts with creatinine to form a red tautomer known as creatinine picrate in the Jaffe method?
Nitric acid
What is the purpose of using Fuller's earth or aluminum magnesium citrate in the Jaffe reaction?
To improve the accuracy of the result
What is the enzyme that catalyzes the reaction of creatine to yield creatine in the enzymatic method of creatinine measurement?
Creatininase
What is the product formed when sarcosine reacts with sarcosine oxidase in the enzymatic method of creatinine measurement?
Glycine, formaldehyde, and hydrogen peroxide
What is the final product that represents the amount of creatinine in the enzymatic method of creatinine measurement?
Water and oxidized indicator
What is the role of peroxidase in the enzymatic method of creatinine measurement?
To oxidize the indicator
What is plasma creatinine inversely proportional to?
Glomerular filtration rate
Why is a 24-hour basis used for urine creatinine measurement?
Because of the endogenous result in the urinary sample
What is not a requirement for plasma creatinine testing?
Fasting
What can plasma creatinine be used to detect?
Kidney stones
What is the relationship between plasma creatinine and diet?
Diet has a negligible effect on plasma creatinine levels
What is used to estimate the glomerular filtration rate?
MDRD formula and blood creatinine
What correction is required for estimating glomerular filtration rate?
For gender and race
When are results of estimated glomerular filtration rate reported as a number?
Only if the result is less than 60
What is the unit of measurement for estimated glomerular filtration rate?
Milliliters per minute per 1.73 square meters
What is estimated by the MDRD formula?
Glomerular filtration rate
What is characterized by an abnormal increase in plasma uric acid concentration?
Gout
What is a possible cause of increased serum uric acid?
Renal disorders
What is Lesch-Nyhan syndrome characterized by?
Overproduction of uric acid and neurological abnormalities
What is a possible cause of decreased serum uric acid?
Severe liver disease
What is an example of a condition that can cause an increase in uric acid production?
All of the above
What is the product of the reaction between uric acid and phosphotungstic acid?
Allantoin, CO2, and tungsten blue
What is the typical reference range for uric acid levels in males?
3.5 - 7.2 mg/dL
What is the wavelength at which the decrease in absorbance is monitored to detect uric acid?
293 nm
What is the enzyme that reacts with uric acid to produce allantoin, hydrogen peroxide, and CO2?
Uricase
What is the typical reference range for uric acid levels in females?
2.6 - 6.0 mg/dL
What is the primary role of hepatocytes in the body?
To convert ammonia to urea
What happens when hepatocytes fail to convert ammonia to urea?
Ammonia accumulates in the blood
What is the condition associated with high levels of ammonia in the blood?
Hyperammonemia
What is the purpose of measuring blood ammonia levels?
To detect inherited metabolic disorders
What type of specimen is required for measuring blood ammonia levels?
Venous blood free of hemolysis
What is the most common cause of increased blood ammonia levels?
Severe liver disease
What is the primary function of glutamate dehydrogenase in the measurement of ammonia?
To catalyze the reaction of alpha-ketoglutarate and ammonia
What is the range of normal plasma ammonia levels?
11-32 μmol/L
What is a potential interference in the measurement of ammonia?
Contamination with ammonia
What is the wavelength used to monitor the decrease in absorbance in the measurement of ammonia?
340 nm
What is the clinical significance of increased plasma ammonia levels?
Hepatic failure and Reye syndrome
Assess your knowledge of non-protein nitrogenous compounds (NPNs) and the synthesis of urea, a crucial indicator of renal function in clinical chemistry. Learn how urea is produced in the liver and excreted by the kidneys. Test your understanding of protein catabolism and amino acid deamination.
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