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CLINICAL CHEMISTRY > Non-Protein Nitrogen Compounds > Flashcards

Non-Protein Nitrogen Compounds Flashcards

1
Q

Product of analytic methodology
requiring removal of protein from sample before analysis

A

Nonportein nitrogen compounds

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2
Q

NPN compounds are used to

A

Monitor renal or kidney function

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3
Q

Concentration of nitrogen-containing compounds was quantified spectrophotometrically by converting nitrogen to

A

Ammonia

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4
Q

Majority of NPN compounds arise from catabolism of

A

Proteins
Nucleic acids

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5
Q

Approximate plasma concentration (% of total NPN)

A

Urea 45-50
Amino Acids 25
Uric Acid 10
Creatinine 5
Creatine 1-2
Ammonia 0.2

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6
Q

Approximate urine concentration (% of excreted)

A

Urea 86.0
Amino Acids -
Uric Acid 1.7
Creatinine 4.5
Creatine -
Ammonia 2.8

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7
Q

NPN with the highest concentration in the blood

A

Urea

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8
Q

Major excretory product of protein metabolism

A

Urea

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9
Q

Organ that synthesize urea

A

Liver

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10
Q

Two forms of urea

A

Blood urea nitrogen (BUN)
Urea nitrogen (UN)

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11
Q

Urea N → Urea concentration

A

Urea N x 2.14

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12
Q

Clinical function of urea

A

Evaluate renal function
Assess hydration status
To determine nitrogen balance
To aid in the diagnosis of renal disease
To verify adequacy of dialysis

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13
Q

Factors that affect concentration of urea in the plasma

A

Protein content of the diet
Rate of protein catabolism
Renal function
Perfusion

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14
Q

Urea is reported in terms of

A

Nitrogen concentration

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15
Q

Chemical Method (Direct Method) for Urea

A

Diacetyl monoxime method

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16
Q

Substrate of Diacetyl monoxime method

A

Urea + DAM

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17
Q

Product of Diacetyl monoxime method

A

Yellow Diazine Derivative

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18
Q

Enzymatic Methods (Indirect Method) for Urea

A

Urease (Urea aminohydrolase)
Coupled Urease/ Glutamate Dehydrogenase method

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19
Q

Proposed reference method for urea

A

Isotope dilution mass spectrometry (IDMS)

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20
Q

Conversion factor of Urea

A

0.357

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21
Q

Specimens for urea measurements

A

Plasma
Serum
Urine

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22
Q

Fasting sample is required for urea measurements. True or False?

A

False; not required

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23
Q

Why cant we use citrate and fluoride in plasma when measuring urea?

A

Citrate and fluoride inhibit urease

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24
Q

Why should we refrigerate urine samples for urea e=measurements?

A

Urea is susceptible to bacterial decomposition

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25
Q

Alevated urea in the blood

A

Azotemia

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26
Q

3 main categories of azotemia

A

Prerenal
Renal
Postrenal

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27
Q

Azotemia as a result of reduced renal blood flow

A

Prerenal azotemia

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28
Q

Pathophysiology of prerenal azotemia

A

Less blood is delivered to the kidney, therefore less urea is being filtered or excreted. Thus, results to increase blood urea nitrogen concentration

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29
Q

Azotemia as a result of diminished glomerular filtration which occurs in wide variety of kidney diseases

A

Renal azotemia

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30
Q

Culprit of renal azotemia

A

Kidney damage or abnormal kidney
function

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31
Q

Azotemia as a result of obstruction of the urine flow and anywhere in the urinary tract by renal calculi, tumors of the bladder or prostate or severe infection

A

Postrenal azotemia

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32
Q

Elevated urea in the blood accompanied by renal failure

A

Uremia

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33
Q

Cause of decreased plasma urea

A

Low protein intake
Severe liver disease

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34
Q

Urea is produced from protein metabolism. True or False?

A

True

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35
Q

BUN or Urea N/Creatinine ratio

A

10:1-20:1

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36
Q

High (>20:1) BUN or Urea N/Creatinine ratio indicates

A

Prerenal and Postrenal azotemia

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37
Q

Low (<20:1) BUN or Urea N/Creatinine ratio indicates

A

Decreased urea production

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38
Q

Reference interval of plasma/serum urea nitrogen

A

6-20 mg/dL

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39
Q

Reference interval 24hr urine urea nitrogen

A

12-20 g/d

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40
Q

The product of catabolism of the purine nucleic acids (adenine and guanine)

A

Uric acid

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41
Q

98-100% of uric acid is reabsorbed in the proximal tubules. True or False?

A

True

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42
Q

Uric acid is soluble in plasma. True or False?

A

False; not soluble

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43
Q

Deposition of uric acid in joints

A

Gout

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44
Q

Deposition of uric acid in tissue

A

Tophi

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45
Q

Organs that convert purines into uric acid

A

Liver

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46
Q

Nearly all of the uric acid in plasma is present as

A

Monosodium urates

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47
Q

Clinical use of uric acid

A

To confirm diagnosis and monitor
treatment of gout
To prevent uric acid nephropathy
during chemotherapeutic treatment
To assess inherited disorders of purine metabolism
To detect kidney dysfunction
To assist in the diagnosis of renal calculi

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48
Q

Chemical method for uric acid measurements

A

Caraway method

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49
Q

Principle of Caraway method

A

Reduction of the phosphotungstic acid to produce tungsten blue

50
Q

Enzymatic methods for uric acid measurements

A

Uricase (urate oxidase)
Peroxidase

51
Q

More specific method for uric acid measurements

A

Uricase method

52
Q

Substrate and product of Uricase (urate oxidase) method

A

Uric acid → allantoin

53
Q

Substrates of Peroxidase method for uric acid measurements

A

Hydrogen peroxide + indicator dye

54
Q

Product of Peroxidase method for uric acid measurements

A

Colored compound

55
Q

Proposed reference method for uric acid

A

Isotope dilution mass spectrometry (IDMS)

56
Q

Specimens for uric acid measurements

A

Heparinized plasma, serum, or urine

57
Q

Anticoagulant of choice for uric acid measurements

58
Q

Urine pH for uric acid measurements

A

Alkaline (8.0)

58
Q

Increased plasma uric acid concentration

A

Hyperuricemia

58
Q

Inherited disorders of purine metabolism

A

Lesch-Nyhan syndrome
Phosphoribosylpyrophosphate
synthetase deficiency

59
Q

Cause of Lesch-Nyhan syndrome

A

Hypoxanthine-guanine
phosphoribosyltransferase deficiency

60
Q

Cause of Fructose Intolerance

A

Fructose-1-phosphate aldolase deficiency

61
Q

Inflammation in joints caused by the deposition of uric acid specifically sodium urate

62
Q

Deposition of uric acid in tissues, causing deformities

63
Q

Ethanol decreases uric acid concentration. True or False?

A

False; increases

64
Q

Decreased plasma uric acid concentration

A

Hypouricemia

65
Q

Causes of decreased uric acid

A

Sever liver disease
Defective tubular reabsorption
Chemotherapy with 6-mercaptopurine or azathioprine
Overtreatment with allopurinol

66
Q

98%-100% of uric acid is reabsorbed in the distal convoluted tubules. True or False?

A

False; PCT

67
Q

Conversion factor of uric acid

68
Q

Reference interval of plasma/serum uric acid in males

A

3.5-7.2 mg/dL

69
Q

Reference interval of plasma/serum uric acid in females

A

2.6-6.0 mg/dL

70
Q

Reference interval of plasma/serum uric acid in children

A

2.0-5.5 mg/dL

71
Q

Reference interval of 24 hour uric acid in adults

A

250-270 mg/d

72
Q

Formed from creatine and creatine phosphate in muscle and is excreted into the plasma at a constant rate related to muscle mass

A

Creatinine

73
Q

Correlation between creatine concentration and muscle mass

A

Directly proportional

74
Q

Correlation between plasma creatine and glomerular filtration rate (GFR)

A

Inversely related

75
Q

Creatine is synthesized primarily in the _____ from _____, _____, and _____

A

Liver
Arginine, glycine, and methionine

76
Q

Creatine will be transported to the muscles to be converted into

A

Creatine phosphate

77
Q

Clinical use of creatinine measurement

A

To determine the sufficiency of kidney function
To determine the severity of kidney damage
To monitor the progression of kidney disease

78
Q

A measure of the amount of creatinine eliminated from the blood by the kidneys, and GFR are used to gauge renal function

A

Creatinine clearance (CrCl)

79
Q

Variables included in Modification of Diet in Renal Disease (MDRD) equation

A

Serum creatinine concentration
Age
Gender (sex)
Ethnicity

80
Q

The standard body surface area in GFR calculation

81
Q

Chemical methods based on Jaffe reaction

A

Jaffe Reaction
Kinetic Jaffe (modified Jaffe method)
Jaffe with adsorbent

82
Q

Substrates of Jaffe Reaction

A

Creatinine + alkaline picrate

83
Q

Product of Jaffe Reaction

A

Red-orange chromogen/reddish chromogen

84
Q

Composition of Jaffe reagent (alkaline picrate)

A

Saturated picric acid and 10% NaOH

85
Q

Interferences in Kinetic Jaffe

A

α-ketoacids and cephalosporins

86
Q

Effect α-ketoacids and cephalosporins in kinetic Jaffe method

A

False increased levels

87
Q

Adsorbent used in Jaffe

A

Fuller’s earth (aluminum magnesium silicate)
Lloyd’s reagent (sodium aluminum silicate)

88
Q

Enzymatic methods for creatinine measurements

A

Creatinine Aminohydrolase-CK method
Creatininase-Hydrogen Peroxide Method

89
Q

Specimen for creatinine/creatine measurements

A

Plasma, serum, urine (refrigerated after collection or frozen if stored longer than 4 days but if it is a timed urine sample then refrigerate during collection period)

90
Q

Drugs that increase creatinine concentration

A

Cephalosporin
Dopamine
Lidocaine

91
Q

Enzymatic method for creatine

A

Creatine aminohydrolase-CK method

92
Q

Chromatography for creatinine/creatine

A

High Performance Liquid Chromatography (HPLC)

93
Q

Increased plasma creatinine indicates

A

Abnormal renal function

94
Q

Increased plasma creatine indicates

A

Muscle disease

95
Q

Correlation between creatine and glomerular filtration rate

A

Inversely related

96
Q

Pathophysiology of muscle disease due to increased plasma creatine

A

Creatine after being produced by the liver is stored in muscles but in muscle diseases creatine escapes and goes to the circulation

97
Q

Conversion factor of creatinine

98
Q

Reference interval of plasma/serum creatinine in males

A

Jaffe method: 0.9-1.3 mg/dL
Enzymatic method: 0.6-1.1 mg/dL

99
Q

Reference interval of plasma/serum creatinine in females

A

Jaffe method: 0.6- 1.1 mg/dL
Enzymatic method: 0.5-0.8 mg/dL

100
Q

Reference interval of plasma/serum creatinine in children

A

Jaffe method: 0.3-0.7 mg/dL
Enzymatic method: 0.0-0.6 mg/dL

101
Q

Reference interval of 24 hour urine creatinine in males

A

Jaffe method: 800-2000 mg/d

102
Q

Reference interval of 24 hour urine creatinine in females

A

Jaffe method: 600-1800 mg/d

103
Q

Produced in the deamination of amino acids during protein metabolism and by bacterial metabolism in the lumen of the intestine

104
Q

How does the body get rid of ammonia?

A

Converted to urea in the liver

105
Q

Free ammonia is nontoxic. True or False?

A

False; toxic

106
Q

Most ammonia in the blood exists as

A

Ammonium ion

107
Q

Enzymatic method for ammonia measurements

A

Glutamate dehydrogenase method

108
Q

Most commonly used method to determine ammonia

A

Glutamate dehydrogenase method

109
Q

Direct measurement of ammonia

A

Ion Selective Electrode (ISE) - Change in pH

110
Q

Product of Dry Slide System: Thin Film Colorimetric Assay

A

Colored compound

111
Q

Suitable anticoagulants for ammonia measurements

A

Heparin
EDTA

112
Q

Samples for ammonia measurements should be centrifuged at _____ within _____ of collection and the plasma or serum should be removed _____

A

0 to 4°C
20 minutes
Immediately

113
Q

Frozen plasma is stable for several days at –20°C. True or False?

114
Q

Source of ammonia
contamination

A

Cigarette smoking

115
Q

Increased plasma ammonia concentration

A

Hyperammonemia

116
Q

Conditions due to hyperammonemia

A

Severe liver disease
Reye’s syndrome
Inherited deficiency of enzymes of the urea cycle

117
Q

Reference interval of plasma ammonia in adult

A

10-60ug/dL

118
Q

Reference interval of 24 urine ammonia in adult

A

140-1500 mg N/d

119
Q

Reference interval of plasma ammonia in children (10d-2y)

A

68-136 ug/dL

CLINICAL CHEMISTRY (10 decks)

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