Unit 4.2 - NPN (Uric Acid)

Question 1

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

Answer 1

Uric acid

Question 2

Readily filtered by glomerulus but undergoes reabsorption and secretion.

Answer 2

Uric acid

Question 3

Uric acid is 98-100% reabsorbed in the:

Answer 3

proximal convuluted tubule

Question 4

<1% of uric acid is excreted in the:

Answer 4

distal tubules

Question 5

70% of uric acid is excreted in the:

Answer 5

renal

Question 6

30% of uric acid is excereted in the:

Answer 6

GI

Question 7

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

Answer 7

7 pH

Question 8

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

Answer 8

urates crystals

Question 9

At what pH does uric acid crystals may form?

Answer 9

<5.75 pH

Question 10

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

Answer 10

gouty arthritis

Question 11

Uric acid measurement is used to: (5)

Answer 11

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.

Question 12

T/F:

Decrease age, decrease waste substance.

Answer 12

True

intake of internal organs = rich in uric acid

Question 13

T/F:

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

Answer 13

True

Question 14

T/F:

Uric acid causes damages to the organs, especially kidneys.

Answer 14

True

Question 15

Uric acid pathophysiology:

Increased: hyperuricemia _ mg/dL

Answer 15

Greater than 6mg/dL

Question 16

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

Answer 16

Gout

Question 17

Gout:

Patients have pain and inflammation of the joints caused by:

Answer 17

precipitation of sodium urates

Question 18

Gout:

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

Answer 18

25-30%

Question 19

Gout:

Formation of:

Answer 19

renal calculi

Question 20

Pathophysiology:

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

Answer 20

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

Question 21

Uric acid is monitored to avoid:

Answer 21

nephrotoxicity

Question 22

Pathophysiology:

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

Answer 22

Xantine oxidase

Question 23

Pathophysiology:

Treatment to inhibit xantine oxidase.

Answer 23

Allopurinol

Question 24

Pathophysiology:

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

Answer 24

Urate oxidase rasburicase

Question 25

# Fill in the blank: Purine catabolism → Hypoxanthine → Xanthine → Uric acid → ___

Answer 25

Allantoin

Question 26

# T/F: Allantoin is readily excretable and is water soluble in urinary excretion.

Answer 26

True

Question 27

# Pathophysiology: Causes of kidney diseases:

Answer 27

Impaired filtration and secretion

Question 28

# 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.

Answer 28

T

Question 29

# T/F: **98-100%** of uric acid reabsorption from glomerular filtrate occurs at the **distal tubules**

Answer 29

F | should be at the proximal convoluted tubules.

Question 30

# T/F: Hyperuricemia may be exacerbated by a purine-rich diet, drugs, alcohol, and genetic variations

Answer 30

T

Question 31

# T/F: Tophi may cause deformities due to crystalline uric acid and urate deposition and may also manifest in proliferative disorders

Answer 31

T

Question 32

An X-linked genetic disorder only seen in males.

Answer 32

Lesch-Nyhan Syndrome

Question 33

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

Answer 33

hypoxanthine-guanine-phosphoribosyltransferase (HPRT)

Question 34

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

Answer 34

hypoxanthine-guanine-phosphoribosyltransferase (HPRT)

Question 35

# Lesch-Nyhan: It consequentially results in _ (increased, decreased) concentrations of uric acid (plasma and urine).

Answer 35

increased

Question 36

What are the chacterization of Lesch-Nyhan Syndrome?

Answer 36

* Neurologic symptoms * Mental retardation * Self-mutilation

Question 37

# Lesch-Nyhan Syndrome: _ (increased, decreased) purine synthesis, _ (increased, decreased) the degradation product

Answer 37

increases, increases

Question 38

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

Answer 38

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

Question 39

Causes of hyperuricemia: (8)

Answer 39

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)

Question 40

* Secondary to severe liver disease * ↓ urea, ↓ uric acid

Answer 40

Hypouricemia

Question 41

# Hypouricemia _ is a defective tubular reabsorption.

Answer 41

Fanconi's syndrome

Question 42

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

Answer 42

6 mercaptopurine or azathiopurine

Question 43

Hypouricemia happens when _ is overtreated.

Answer 43

allopurinol

Question 44

# Analytical methods: Direct REDOX Method

Answer 44

Caraway/Henry's Method

Question 45

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

Answer 45

Caraway/Henry's Method

Question 46

# Analytical methods: Product of Caraway/Henry's Method:

Answer 46

tungsten blue

Question 47

# Analytical methods: Based on the **oxidation of UA** in PFF and **reduction of PTA**

Answer 47

Caraway/Henry's Method

Question 48

# Analytical methods: Interferences on Caraway/Henry's Method: (5)

Answer 48

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

Question 49

# Analytical methods: Iron reduction method reduces ferric ion to ferrous ion using what?

Answer 49

Ligand

Question 50

# Analytical methods: Product of Iron Reduction Method:

Answer 50

ferrous ion + chromophore

Question 51

# Analytical methods: Conversion of uric acid to allantoin using uricase.

Answer 51

Enzymatic methods

Question 52

# Enzymatic methods of uric acid: This method measures differential absorption of UA and allantoin at 290-293 nm.

Answer 52

Uricase Method (Blauch and Koch)

Question 53

# Enzymatic methods of uric acid: Advantage of Uricase Method (Blauch and Koch): (1)

Answer 53

more specific = NEEDS SPECTROPHOTOMETRY!

Question 54

# Enzymatic methods of uric acid: Disadvantages of Uricase Method (Blauch and Koch): (2)

Answer 54

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

Question 55

# T/F: Negative interference in Uricase Method is caused by hemolysed sample, causing the release of Hgb.

Answer 55

True

Question 56

# Enzymatic methods of uric acid: UA + O2 + 2 H2O → **allantoin** + CO2 + H2O2

Answer 56

Uricase method (Blauch and Koch)

Question 57

# Enzymatic methods of uric acid: 1. UA + O2 + 2 H2O → **allantoin** + CO2 + H2O2 2. H2O2 + indicator dye → colored compound + 2 or 3 H2O

Answer 57

Coupled Enzymatic Method

Question 58

# Enzymatic methods of uric acid: Disadvantage of couplez enzymatic method:

Answer 58

Bilirubin and ascorbic acid may destroy peroxide | Falsely decreased: reducing agent, inhibiting glucose oxidase

Question 59

# Enzymatic methods of uric acid: Remedy in preventing the false decrease of bilirubin and ascorbic acid in coupled enzymatic method.

Answer 59

addition of potassium ferricyanide and ascorbate oxidase

Question 60

Reference method in Uric Acid Determination:

Answer 60

IDMS

Question 61

Specimen requirements in Uric Acid:

Answer 61

heparinized plasma, serum, or urine | green top! :)

Question 62

# T/F: Diet may affect uric acid concentration.

Answer 62

True

Question 63

# T/F: Gross lipemia should be avoided.

Answer 63

T

Question 64

# T/F: hemolysis, with concomitant glutathione release, may result in **HIGH** values.

Answer 64

T

Question 65

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

Answer 65

1. Salicylates 2. Thiazides

Question 66

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

Answer 66

3-5 days

Question 67

What tubes should not be used in measuring Uric Acid?

Answer 67

EDTA Tube (Lavender) Sodium Fluoride (Gray)

Question 68

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

Answer 68

alkaline; pH 8

Question 69

Reference intervals of plasma/serum for male:

Answer 69

3.5-7.2 mg/dL

Question 70

Reference intervals of plasma/serum for female:

Answer 70

2.6-6.0 mg/dL

Question 71

Reference intervals of plasma/serum for child:

Answer 71

2.0-5.5 mg/dL

Question 72

Reference intervals of 24-hour urine for adult:

Answer 72

250/750 mg/day

Question 73

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

Answer 73

IDMS