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Which of the following is NOT an advantage of the DAM method?
What reaction is utilized in the measurement of urea using DAM?
What is the standard method for measuring urea in reference laboratories due to its high cost?
Which components intensify the reaction of urea with DAM?
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What should be avoided to ensure accurate urea measurements?
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Which of the following methods does NOT require deproteinization of samples?
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What is the effect of fluoride and citrate on the urease enzyme?
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During which reaction does urea convert into CO2 and NH3?
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What is a major disadvantage of the Direct Jaffe Reaction Method?
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Which of the following reagents is used to eliminate interferences in the Direct Jaffe Reaction Method?
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What is the advantage of the Kinetic Jaffe Method over the Direct Jaffe Reaction Method?
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Which wavelengths are typically used to reveal the level of creatinine in enzymatic methods?
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What type of samples can be accurately used for creatinine measurement?
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Which of the following is a direct method for measuring urea levels?
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Which is identified as the ultimate reference standard for creatinine measurement?
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What is the primary principle behind the Micro-Kjeldahl method?
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What condition can affect the accuracy of Jaffe and enzymatic assays?
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What is the correct relationship between Blood Urea Nitrogen (BUN) and urea?
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What should be done with urine samples if they need to be stored for more than four days?
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Which of the following techniques is known as an indirect method for measuring urea?
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Which of the following is NOT associated with the Micro-Kjeldahl method?
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Which of the following substances is used in Nessler's reaction for ammonia measurement?
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Which analytical technique is considered a classical reference method for measuring nitrogen?
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What color indicates a positive outcome in the Berthelot reaction?
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What is the primary basis for protein measurement in the Kjeldahl method?
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Which factor may lead to inaccurate results in enzymatic assays?
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What is the effect of lipemia on laboratory results?
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What is the required reaction environment for the Biuret method to work effectively?
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Which reagent is primarily used in the Kjeldahl method to digest the sample?
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At what wavelength is protein concentration measured in the Biuret method?
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What is a common characteristic of total protein levels at birth?
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Which of the following methodologies is NOT included in the provided list of lab methodologies for protein measurement?
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What happens to albumin concentration as the severity of liver disease increases?
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Which measurement method produces a violet color to identify albumin?
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What is the most specific dye used for measuring albumin?
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Which of the following conditions is associated with a decreased albumin concentration?
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What is the reference range for the Albumin/Globulin (A/G) ratio?
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Increased globulin levels can indicate which of the following conditions?
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What is the conversion factor from conventional to SI units for albumin?
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Which method for albumin determination binds to small molecules and specific dyes?
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Study Notes
Non-Protein Nitrogen
- Non-Protein Nitrogen (NPN) tests measure waste products in the blood that are not protein.
- NPN levels can indicate kidney function, as the kidneys are responsible for filtering these waste products from the blood.
Urea
- Urea is a major waste product produced by the body during protein metabolism.
- It is formed in the liver and transported to the kidneys, where it's excreted in urine.
- Increased urea levels can indicate kidney dysfunction, dehydration, high protein intake, and other conditions.
Laboratory Methods
- Direct methods: Directly measure urea levels in the blood.
- Indirect methods (Blood Urea Nitrogen - BUN): Assess the nitrogen content in urea, which can be converted to urea concentration.
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Micro-Kjeldahl (Indirect): A classic method using a strong acid to digest urea and convert nitrogen to ammonia.
- Ammonia is measured with Nessler's reagent, which reacts with ammonia to form a yellow complex.
- Berthelot's reaction uses phenol and hypochlorite to react with ammonia, creating blue coloration.
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Diacetyl Monoxime (DAM) (Direct): A simple, direct method that uses a strong acid to react with urea, forming a yellow diazine derivative.
- This reaction is intensified by ferric ions and thiosemicarbazide, resulting in a red color measured at 540 nm.
- This method avoids interference from ammonia.
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Enzymatic Method (Indirect): Uses urease enzyme to break down urea into ammonia and carbon dioxide.
- The ammonia can then be measured using either Nessler's reagent or Berthelot's reaction.
- A coupled urease/glutamate dehydrogenase (GLDH) method is also available.
- Isotope Dilution/Mass Spectrometry: This is the gold standard for urea measurement, but it's expensive and typically performed only in reference laboratories.
Precautions and Specimen Considerations
- Specimens: Plasma, serum, or urine.
- Non-hemolyzed samples are preferred, as hemolysis can interfere with certain tests.
- Avoid contamination with ammonium salts.
- Prevent prolonged standing as urea can convert to ammonia.
- Refrigerate specimens, especially urine and timed urine samples, if not analyzed within a few hours.
Creatinine
- Creatinine is a waste product produced by the breakdown of muscle tissue.
- It's filtered by the kidneys and excreted in urine.
- Elevated creatinine levels indicate impaired kidney function.
Laboratory Methods
-
Direct Jaffe Reaction Method:
- Creatinine in a protein-free filtrate reacts with alkaline picrate solution to form a red-orange complex.
- This method is susceptible to interference from various substances like ketones, glucose, fructose, and protein.
- To improve specificity, Lloyd's reagent or Fuller's Earth reagent can be used to remove interferences.
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Kinetic Jaffe Method:
- Measures the rate of color development from the reaction of creatinine with alkaline picrate.
- This method is less susceptible to interference and is widely used in automated systems.
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Enzymatic Methods:
- Utilize enzymes specific for creatinine, eliminating interference from other substances.
- These methods are more accurate and less prone to interference.
- Isotope Dilution / Mass Spectrometry: The ultimate reference standard for creatinine measurement.
Precautions and Specimen Considerations
- Avoid hemolyzed samples.
- Lipemic and icteric samples can interfere with creatinine measurement.
- Fasting is not required.
- Urine: Refrigerate it after collection.
- For long-term storage, freeze urine samples.
Uric Acid
- Uric acid is a waste product produced by the breakdown of purines, molecules found in nucleic acids.
- The liver converts purines into uric acid, which is then filtered by the kidneys and excreted in urine.
- Elevated uric acid levels (hyperuricemia) can contribute to gout, kidney stones, and other conditions.
Laboratory Methods
-
Uric Acid Oxidase-uricase Method:
- Uses the enzyme uricase to convert uric acid into allantoin.
- This method is widely used and highly specific.
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Enzymatic Methods:
- Utilize other enzymes coupled with uricase, such as peroxidase, to enhance sensitivity and accuracy.
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Spectrophotometric Methods:
- Measure absorbance at specific wavelengths to quantify uric acid concentration.
Precautions and Specimen Considerations
- Avoid hemolyzed samples.
- Fasting is not required.
- Store specimens appropriately.
Ammonia
- Ammonia is a waste product produced by the breakdown of amino acids.
- The liver converts ammonia into urea, which is then excreted by the kidneys.
- Elevated ammonia levels can indicate liver dysfunction.
Laboratory Methods
-
Enzymatic Methods (GLDH):
- Utilize enzymes that catalyze reactions involving ammonia, such as glutamate dehydrogenase.
- This method measures the change in absorbance at specific wavelengths to quantify ammonia concentration.
- Ion Selective Electrodes: A direct method that measures the concentration of ammonia in blood samples using an electrode sensitive to ammonia.
Precautions and Specimen Considerations
- Blood samples should be collected with a minimum of stasis.
- Avoid hemolyzed samples.
- Analyze samples promptly.
Other Tests for Kidney Function
- Glomerular filtration rate (GFR): Measures the rate at which the kidneys filter waste products from the blood.
- Creatinine clearance: Calculates the amount of creatinine excreted in urine over a specific time period.
- Proteinuria: The presence of protein in the urine, which can indicate kidney damage.
- Microscopic urine analysis: Examines urine sediment for abnormalities, such as red blood cells, white blood cells, and casts.
- Blood urea nitrogen (BUN)/creatinine ratio: Can help differentiate between pre-renal, renal, and post-renal causes of kidney dysfunction.
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Description
This quiz explores the concepts of Non-Protein Nitrogen (NPN) and urea in relation to kidney function. It covers the methods for measuring NPN and urea levels, as well as their implications for health. Test your knowledge on laboratory techniques and the significance of waste products in blood analysis.
