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MT 6317 LEC: CLINICAL CHEMISTRY > Unit 4.2 - NPN (Uric Acid) > Flashcards

Unit 4.2 - NPN (Uric Acid) Flashcards

1
Q

Product of catabolism of purines bases (adenine & guanine).

A

Uric acid

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2
Q

Readily filtered by glomerulus but undergoes reabsorption and secretion.

A

Uric acid

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3
Q

Uric acid is 98-100% reabsorbed in the:

A

proximal convuluted tubule

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4
Q

<1% of uric acid is excreted in the:

A

distal tubules

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5
Q

70% of uric acid is excreted in the:

A

renal

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6
Q

30% of uric acid is excereted in the:

A

GI

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7
Q

Uric acid is relatively insoluble in plasma as monosodium urate at pH of:

A

7 pH

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8
Q

At concentration of >6.8 mg/dL, plasma is saturated ____ may form in the tissues.

A

urates crystals

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9
Q

At what pH does uric acid crystals may form?

A

<5.75 pH

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10
Q

High concentrations accumulate in the joints and tissue resulting in inflammation:

A

gouty arthritis

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11
Q

Uric acid measurement is used to: (5)

A
  1. confirm diagnosis and monitor treatment of gout;
  2. assess and prevent uric acid nephropathy during chemotherapeutic management;
  3. assess inherited disorders of purine metabolism;
  4. detect kidney dysfunction; and
  5. assist in the diagnosis of renal calculi.
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12
Q

T/F:

Decrease age, decrease waste substance.

A

True

intake of internal organs = rich in uric acid

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13
Q

T/F:

Uric acid nephropathy is common in cancer patients, resulting of rapid breakdown of cells, leading to hyperuricidemia.

A

True

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14
Q

T/F:

Uric acid causes damages to the organs, especially kidneys.

A

True

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15
Q

Uric acid pathophysiology:

Increased: hyperuricemia _ mg/dL

A

Greater than 6mg/dL

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16
Q

Happens in male between 30 and 50 years of age; in female, they appear after menopausal

A

Gout

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17
Q

Gout:

Patients have pain and inflammation of the joints caused by:

A

precipitation of sodium urates

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18
Q

Gout:

In hyperuricemia, __% of patients results of overproduction of uric acid.

A

25-30%

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19
Q

Gout:

Formation of:

A

renal calculi

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20
Q

Pathophysiology:

Uric acid is increased in nuclear breakdown, and is usually seen in patient undergoing: (4)

A
  1. chemotherapy for leukemia
  2. lymphoma
  3. multiple myeloma
  4. polycythemia
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21
Q

Uric acid is monitored to avoid:

A

nephrotoxicity

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22
Q

Pathophysiology:

This enzyme prevents the formation of uric acid and is slow acting.

A

Xantine oxidase

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23
Q

Pathophysiology:

Treatment to inhibit xantine oxidase.

A

Allopurinol

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24
Q

Pathophysiology:

This enzyme is given for managing uric acid, fast-acting, and at risk of developing methemoglobinuria.

A

Urate oxidase rasburicase

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25
Q

Fill in the blank:

Purine catabolism → Hypoxanthine → Xanthine → Uric acid → ___

A

Allantoin

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26
Q

T/F:

Allantoin is readily excretable and is water soluble in urinary excretion.

A

True

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27
Q

Pathophysiology:

Causes of kidney diseases:

A

Impaired filtration and secretion

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28
Q

T/F:

Nearly all of the uric acid in the plasma is present as monosodium urate and at pH less than 5.75 acid crystals may form in the urine.

A

T

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29
Q

T/F:

98-100% of uric acid reabsorption from glomerular filtrate occurs at the distal tubules

A

F

should be at the proximal convoluted tubules.

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30
Q

T/F:

Hyperuricemia may be exacerbated by a purine-rich diet, drugs, alcohol, and genetic variations

A

T

31
Q

T/F:

Tophi may cause deformities due to crystalline uric acid and urate deposition and may also manifest in proliferative disorders

A

T

32
Q

An X-linked genetic disorder only seen in males.

A

Lesch-Nyhan Syndrome

33
Q

Lesch-Nyhan Syndrome is caused by the complete deficiency of what enzyme?

A

hypoxanthine-guanine-phosphoribosyltransferase (HPRT)

34
Q

The lack of this enzyme prevents the reutilization of purine bases in the nucleotide salvage pathway. What enzyme is this?

A

hypoxanthine-guanine-phosphoribosyltransferase (HPRT)

35
Q

Lesch-Nyhan:

It consequentially results in _ (increased, decreased) concentrations of uric acid (plasma and urine).

A

increased

36
Q

What are the chacterization of Lesch-Nyhan Syndrome?

A
  • Neurologic symptoms
  • Mental retardation
  • Self-mutilation
37
Q

Lesch-Nyhan Syndrome:

_ (increased, decreased) purine synthesis, _ (increased, decreased) the degradation product

A

increases, increases

38
Q

What are the other conditions with increased Uric Acid? (3)

A
  1. Mutations on phosphoribosylpyrophosphate synthetase
  2. Toxemia on pregnancy
  3. Lactic acidosis (competition for binding sites in renal tubules)
39
Q

Causes of hyperuricemia: (8)

A
  1. Increased dietary intake of purine rich food
  2. Increased urate production (postmenopausal women, increased tissue catabolism such as in starvation)
  3. Decreased excretion
  4. Catabolic pathways enzyme defects
  5. Increased metabolism of cell nuclei (lymphoma, leukemia, multiple myeloma, polycythemia, hemolytic and megaloblastic anemia)
  6. Inherited disorders with enzyme deficiency (Lesch-Nyhan Syndrome)
  7. Decreased uric acid excretion (preeclampsia, lactic acidosis)
  8. Chronic renal disease (impaired filtration and secretion)
40
Q
  • Secondary to severe liver disease
  • ↓ urea, ↓ uric acid
A

Hypouricemia

41
Q

Hypouricemia

_ is a defective tubular reabsorption.

A

Fanconi’s syndrome

42
Q

Hypouricemia occurs in chemotherapy with _ or _ (inhibits de novo purine synthesis)

A

6 mercaptopurine or azathiopurine

43
Q

Hypouricemia happens when _ is overtreated.

A

allopurinol

44
Q

Analytical methods:

Direct REDOX Method

A

Caraway/Henry’s Method

45
Q

Analytical methods:

Uric acid + phosphotungstic acid + O 2 - - NaCO 3/OH- → tungsten blue + allantoin + CO 2

A

Caraway/Henry’s Method

46
Q

Analytical methods:

Product of Caraway/Henry’s Method:

A

tungsten blue

47
Q

Analytical methods:

Based on the oxidation of UA in PFF and reduction of PTA

A

Caraway/Henry’s Method

48
Q

Analytical methods:

Interferences on Caraway/Henry’s Method: (5)

A

False (+) / increased in:
* turbidity
* aspirin and metabolite
* acetaminophen
* caffeine
* theophylline

49
Q

Analytical methods:

Iron reduction method reduces ferric ion to ferrous ion using what?

A

Ligand

50
Q

Analytical methods:

Product of Iron Reduction Method:

A

ferrous ion + chromophore

51
Q

Analytical methods:

Conversion of uric acid to allantoin using uricase.

A

Enzymatic methods

52
Q

Enzymatic methods of uric acid:

This method measures differential absorption of UA and allantoin at 290-293 nm.

A

Uricase Method (Blauch and Koch)

53
Q

Enzymatic methods of uric acid:

Advantage of Uricase Method (Blauch and Koch): (1)

A

more specific = NEEDS SPECTROPHOTOMETRY!

54
Q

Enzymatic methods of uric acid:

Disadvantages of Uricase Method (Blauch and Koch): (2)

A
  1. protein cause high background absorbance
  2. negative interference due to Hb and xantine
55
Q

T/F:

Negative interference in Uricase Method is caused by hemolysed sample, causing the release of Hgb.

A

True

56
Q

Enzymatic methods of uric acid:

UA + O2 + 2 H2O → allantoin + CO2 + H2O2

A

Uricase method (Blauch and Koch)

57
Q

Enzymatic methods of uric acid:

  1. UA + O2 + 2 H2O → allantoin + CO2 + H2O2
  2. H2O2 + indicator dye → colored compound + 2 or 3 H2O
A

Coupled Enzymatic Method

58
Q

Enzymatic methods of uric acid:

Disadvantage of couplez enzymatic method:

A

Bilirubin and ascorbic acid may destroy peroxide

Falsely decreased: reducing agent, inhibiting glucose oxidase

59
Q

Enzymatic methods of uric acid:

Remedy in preventing the false decrease of bilirubin and ascorbic acid in coupled enzymatic method.

A

addition of potassium ferricyanide and ascorbate oxidase

60
Q

Reference method in Uric Acid Determination:

A

IDMS

61
Q

Specimen requirements in Uric Acid:

A

heparinized plasma, serum, or urine

green top! :)

62
Q

T/F:

Diet may affect uric acid concentration.

A

True

63
Q

T/F:

Gross lipemia should be avoided.

A

T

64
Q

T/F:

hemolysis, with concomitant glutathione release, may result in HIGH values.

A

T

65
Q

What are the 2 enzymes that increases the values for uric acid?

A
  1. Salicylates
  2. Thiazides
66
Q

Serum sample may be stored refrigerated for _ to _ days.

A

3-5 days

67
Q

What tubes should not be used in measuring Uric Acid?

A

EDTA Tube (Lavender)
Sodium Fluoride (Gray)

68
Q

Urine specimen in measuring UA should be _ and has a pH of _.

A

alkaline; pH 8

69
Q

Reference intervals of plasma/serum for male:

A

3.5-7.2 mg/dL

70
Q

Reference intervals of plasma/serum for female:

A

2.6-6.0 mg/dL

71
Q

Reference intervals of plasma/serum for child:

A

2.0-5.5 mg/dL

72
Q

Reference intervals of 24-hour urine for adult:

A

250/750 mg/day

73
Q

What is the methodology for UA determination is free of interferences and considered reference?

A

IDMS

MT 6317 LEC: CLINICAL CHEMISTRY (3 decks)

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