NPN

Question 1

UREA

Enzymatic Method
Chemical Method

Answer 1

GLDH coupled enzyme
Indicator dye
Conductimetric (ISE)

Fearon’s reaction

Question 2

UREA

First step

Answer 2

Urea + 2 H2O –Urease 2 NH4+ + CO3 2-

Question 3

GLDH coupled enzyme disappearance of NADH at ___

NH4+ + 2-oxoglutarate + NADH + H+ _____ glutamate + NAD+ + H2O

Answer 3

340 nm

NH4+ + 2-oxoglutarate + NADH + H+  GLDH  glutamate + NAD+ + H2O

Question 4

Indicator dye

Answer 4

NH4+ + pH Indicator  color change
Nessler’s reaction (HgI2/KI)
Berthelot’s reaction (Alk. hypochlorite)

Question 5

Conductimetric (ISE)

Answer 5

Conversion of unionized urea to NH4+ and CO32- results in increased conductivity

Question 6

Fearon’s reaction

Urea + DAM (____.)  ____ (Diazine dirivative)

Answer 6

Urea + DAM (Diacetyl Monoxime Mtd.)  Yellow solution (Diazine dirivative)

Question 7

Plasma or serum

Urine, 24 hour

Answer 7

6 – 20 mg/dL - 2.1-7.1 mmol/L

12-20 g/day - 11.5-4.4 mmol urea/day

Question 8

Specimen Considerations

Answer 8

1. Use fasting blood
2. Avoid fluoride or citrate anticoagulants
3. Refrigerate Samples

Question 9

(↑ urea in the blood)

Answer 9

Azotemia

Question 10

Azotemia 3

Answer 10

Prerenal
Renal (Uremia)
Postrenal

Question 11

Reduce blood flow or ↑ protein catabolism

Answer 11

Prerenal

Question 12

Damage of nephrons (Renal failure/disease)

Answer 12

Renal (Uremia)

Question 13

Urinary tract obstruction (calculi, tumors)

Answer 13

Postrenal

Question 14

Azotemia

4 Decreased Concentration

Answer 14

Low protein intake
Severe vomiting and diarrhea
Liver disease
Pregnancy

Question 15

URIC ACID

1. Physiology

Answer 15

Major end-product of purine catabolism.

Present as monosodium urates in plasma (98-100% reabsorbed)

May precipitate in tissues (blood pH ≈ 7 ; BUA > 6.8 mg/dL )

Question 16

URIC ACID

2. Clinical Application

Answer 16

Inherited disorders of purine metabolism
Gout
Renal calculi
Uric acid nephropathy (chemotheraphy)
Kidney dysfunction

Question 17

URIC ACID

Enzymatic Methods
Chemical Method

Answer 17

Spectrophotometric
(Blauch and Koch)

Coupled enzyme (I) 
Catalase

Coupled enzyme (II) 
Peroxidase

Phosphotungstic acid
(Caraway method)

Question 18

URIC ACID
First step
Uric Acid + O2 +2 H2O –____ ____ + CO2 + ____

Answer 18

Uric Acid + O2 +2 H2O –Uricase allantoin + CO2 + H2O2

Question 19

Spectrophotometric
(Blauch and Koch)
↓ absorbance at ___

Answer 19

↓ absorbance at 293 nm

Uric acid v. allantoin

Question 20

Coupled enzyme (I)
Catalase
H2O2 + reagent –____ colored compound

Answer 20

H2O2 + reagent –Catalase colored compound

Question 21

Coupled enzyme (II) Peroxidase
H2O2  + indicator dye –\_\_\_\_\_ - \_\_\_\_

Answer 21

H2O2 + indicator dye –Peroxidase Red dye

Question 22

Phosphotungstic acid
(Caraway method)
Uric Acid + H3PW12O4o + O2
- ______ allantoin + ____ + CO2

Answer 22

Uric Acid + H3PW12O4o + O2
- Na2CO3/OH- 
allantoin + tungsten blue + CO2

Question 23

Specimen Considerations

urea 3

Answer 23

1. Heparinized plasma, serum or urine
2. Lipemia, bilirubin, hemolysis (↓ UA)
3. Salicylates and thiazides (↑ UA)

Question 24

Hyperuricemia (Enzyme deficiencies)

Answer 24

1) Lesch-Nyhan syndrome
2) Glycogen storage disease type 1
3) Fructose intolerance
4) Hemolytic and proliferative process
5) Treatment of myeloproliferative disease w/ cytotoxic drugs
6) Chronic renal disease
7) Toxemia of pregnancy and lactic acidosis
8) Purine-rich diet

Question 25

Lesch-Nyhan syndrome

Answer 25

↓ HGPRT | ↓ reutilization of purine, ↑ synthesis of purine

Question 26

Glycogen storage disease type 1

Answer 26

↓ G-6-P | ↑ triglycerides, ↓ renal urate excretion

Question 27

Fructose intolerance

Answer 27

↓ F1PA | ↑ lactate, ↓ renal urate excretion

Question 28

Hypouricemia | 5

Answer 28

``` ↓ PRPP Synthetase Liver disease Fanconi sydrome Chemotheraphy with azathioprine or 6-mercaptopurine Overtreatment with allopurinol ```

Question 29

↓ PRPP Synthetase

Answer 29

↓ de novo purine synthesis

Question 30

Liver disease

Answer 30

↓ uric acid synthesis

Question 31

Fanconi sydrome

Answer 31

Defective tubular reabsorption

Question 32

Chemotheraphy with azathioprine or 6-mercaptopurine

Answer 32

↓ de novo purine synthesis

Question 33

Overtreatment with allopurinol

Answer 33

↓ XO, ↓ de novo purine synthesis

Question 34

CREATININE | Physiology

Answer 34

Chief product of muscle metabolism | Not affected by protein diet

Question 35

CREATININE | 2. Clinical Application

Answer 35

Sufficiency of kidney function Severity of kidney damage Progression of kidney disease Completeness of 24-hour urine

Question 36

Volume of plasma filtered (V) by the glomeruli per unit of time (mL/minute)

Answer 36

Glomerular filtration rate (Creatinine clearance)

Question 37

GFR = V/t

Answer 37

GFR = UCrVu ------------ x 1.73/A PCrt

Question 38

CREATININE | Chemical Method

Answer 38

Jaffe Reaction Jaffe-kinetic Jaffe with adsorbent

Question 39

CREATININE | Principle

Answer 39

Creatinine + picrate  Red-orange complex

Question 40

CREATININE | Jaffe-kinetic

Answer 40

Rate of change of absorbance(color formation)

Question 41

Principle | Jaffe with adsorbent

Answer 41

PFF is adsorbed first onto Fuller’s earth (aluminum magnesium silicate)

Question 42

CREATININE 6 Falsely ↑

Answer 42

``` Glucose α-ketoacids Ascorbate Uric Acid Cephalosporins Dopamine ```

Question 43

CREATININE 3 Falsely ↓

Answer 43

1. Bilirubin 2. Hemoglobin 3. Lipemic specimens

Question 44

CREATININE | Increased Concentration

Answer 44

``` Renal failure (glomerular function) ↑ Plasma Concentration = ↓ GFR ```

Question 45

AMMONIA | 1. Physiology

Answer 45

By product of amino acid deamination. | Converted to urea in the liver.

Question 46

AMMONIA | 2. Clinical Application

Answer 46

Hepatic failure and hepatic coma Reye’s syndrome Inherited deficiencies of urea cycle

Question 47

AMMONIA Chemical Method Enzymatic Method

Answer 47

Ion-selective electrode Spectrophotometric GLDH ↓ absorbance (340 nm)

Question 48

Chemical Method Principle -Ion-selective electrode Diffusion of ___ through selective membrane into ___ causing pH change. -Spectrophotometric -Enzymatic Method GLDH NH4+ + 2-oxoglutarate + ____ + H+ ____ Glutamate + NADP+ + H2O

Answer 48

NH3 NH4Cl NH3 + bromphenol blue  blue dye NH4+ + 2-oxoglutarate + NADPH + H+ GLDH Glutamate + NADP+ + H2O

Question 49

AMMONIA | Specimen Considerations

Answer 49

1. Heparinized and EDTA tubes 2. Samples is centrifuged at 0-4°C within 20 mins. of collection and the plasma/serum removed 3. Avoid cigarette smoking for several hours