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Clinical Chemistry > NPN UREA > Flashcards

NPN UREA Flashcards

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1
Q

NPN present in highest concentration in blood?

A

Urea

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2
Q

Where is urea formed and from what substances?

A

Liver from CO2 and ammonia

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3
Q

Major excretory product of protein metabolism?

A

Urea

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4
Q

How is urea concentration expressed?

A

In terms of nitrogen content (BUN)

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5
Q

Conversion factor for BUN to urea?

A

BUN x 2.14 = Urea

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6
Q

Reference method for measuring urea?

A

Isotope Dilution Mass Spectrometry (IDMS)

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7
Q

Reagent used in Fearon method for BUN measurement

A

Diacetyl monoxime

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8
Q

Product formed in Fearon method for BUN measurement

A

Diazine

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9
Q

Color observed in Fearon method for BUN measurement

A

Yellow

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10
Q

Reagent used in Nesslerization method for BUN measurement

A

K2(HgI4)

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11
Q

Color observed in Nesslerization method for BUN measurement

A

Yellow

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12
Q

Reagent used in Berthelot method for BUN measurement

A

Sodium hypochlorite (NaOCl) and phenol

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13
Q

Color observed in Berthelot method for BUN measurement

A

Blue

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14
Q

Enzyme used in enzymatic BUN measurement

A

Urease

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15
Q

Product formed in enzymatic BUN method

A

2 NH4+ + CO3²-

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16
Q

Enzyme used in GLDH-coupled enzymatic method for BUN measurement

A

Glutamate dehydrogenase (GLDH)

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17
Q

Product formed in GLDH-coupled enzymatic method for BUN measurement

A

Glutamate and NAD

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18
Q

Method used for measuring BUN by conductivity

A

Conductimetric method

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19
Q

Reference range for BUN

A

6–20 mg/dL

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20
Q

Condition associated with high BUN in prerenal azotemia

A

Dehydration, ↓ blood volume

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21
Q

Condition associated with high BUN in renal azotemia

A

Glomerulonephritis, renal failure

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22
Q

Condition associated with high BUN in postrenal azotemia

A

Urinary tract obstruction

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23
Q

Condition associated with very high plasma urea concentration and renal failure

A

Uremia/Uremic syndrome

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24
Q

Conditions that can cause low BUN

A

Repeated dialysis, liver disease, low protein diet

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25
Q

Normal BUN/Creatinine ratio

A

10-20 BUN : 1 creatinine

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26
Q

Most common cause of prerenal azotemia

A

Dehydration

27
Q

BUN/Creatinine ratio indicating prerenal azotemia

A

> 20:1

28
Q

Other causes of prerenal azotemia

A

Decreased blood volume, high-protein diet, increased protein catabolism

29
Q

BUN/Creatinine ratio in renal azotemia

A

~20:1

30
Q

Cause of renal azotemia

A

Decreased excretion (glomerulonephritis, renal failure)

31
Q

BUN/Creatinine ratio in postrenal azotemia

A

~20:1

32
Q

Causes of postrenal azotemia

A

Urinary tract obstruction, nephrolithiasis, tumors, severe infections

33
Q

Condition with very high plasma urea in renal failure

A

Uremia/Uremic syndrome

34
Q

BUN/Creatinine ratio indicating low BUN

A

< 10:1

35
Q

Causes of low BUN

A

Repeated dialysis, liver disease, low-protein diet

36
Q

Substances creatinine is derived from

A

Methionine, glycine, arginine

37
Q

Factor affecting creatinine excretion rate

A

Muscle mass

38
Q

How is creatinine eliminated from circulation?

A

By glomerular filtration

39
Q

Relationship between creatinine concentration and GFR

A

Inversely related

40
Q

Characteristics of the Jaffe reaction

A

Colorimetric, endpoint, nonspecific; interference from ascorbic acid, glucose, uric acid

41
Q

Product of the Jaffe reaction

A

Red-orange tautomer

42
Q

Methods to improve specificity of the Jaffe reaction

A

Kinetic method, adsorbents (Lloyd’s RGT, Fuller’s earth)

43
Q

Enzyme used in enzymatic creatinine methods

A

Creatininase

44
Q

Reaction catalyzed by creatininase

A

Creatinine + H2O → Creatine

45
Q

Final chromogen reaction in POD-coupled method

A

H2O2 + chromogen → Oxidized chromogen + H2O

46
Q

Reaction catalyzed by CK in creatininase-CK method

A

Creatine + ATP → Creatine phosphate + ADP

47
Q

Role of LDH in CK-coupled method

A

Converts pyruvate + NADH → lactate + NAD+

48
Q

Absorbance change indicating low creatinine in CK-coupled methods

A

Low absorbance from NAD+ formation

49
Q

Effect of high NADH on absorbance in CK-coupled methods

A

High NADH causes high absorbance

50
Q

Formula for Creatinine Clearance

A

Creatinine clearance = (UV/P) × 1.73/A (A = body surface area in m²)

51
Q

MDRD formula for eGFR (mL/min/1.73m²)

A

eGFR = 170 × Cr^-0.999 × Age^-0.176 × 1.180 (if Black) × 0.762 (if female) × BUN^-0.170 × Alb^-0.318

52
Q

Alternative MDRD formula for eGFR

A

eGFR = 186 × Cr^-1.154 × Age^-0.203 × 1.212 (if Black) × 0.742 (if female)

53
Q

Difference between old and new MDRD formulas

A

Old MDRD: 6 variables; New MDRD: 4 variables

54
Q

CKD-EPI formula for eGFR

A

eGFR = 141 × min(SCr/k,1)^a × max(SCr/k,1)^-1.209 × 0.993^Age × 1.018 (if female) × 1.159 (if Black)

55
Q

Reference value for Serum Creatinine (Jaffe method)

A

0.9–1.3 mg/dL (M); 0.6–1.1 mg/dL (F)

56
Q

Reference value for Serum Creatinine (enzymatic method)

A

0.6–1.1 mg/dL (M); 0.5–0.8 mg/dL (F)

57
Q

Reference value for Creatinine Clearance

A

M = 85-125 mL/min; F = 75-115 mL/min

58
Q

Clinical significance of decreased creatinine clearance or eGFR

A

Indicates impaired renal function

59
Q

Stages of CKD based on GFR

A

Stage 1: GFR ≥ 90, Stage 2: GFR 60-89, Stage 3: GFR 30-59, Stage 4: GFR 15-29, Stage 5: GFR < 15

60
Q

Stage 1 CKD classification

A

Kidney damage with normal or increased GFR (GFR ≥ 90)

61
Q

Definition of Stage 2 CKD

A

Kidney damage with normal or decreased GFR (GFR 60-89)

62
Q

Definition of Stage 3 CKD

A

Moderate decreased GFR (GFR 30-59)

63
Q

Definition of Stage 4 CKD

A

Severe decreased GFR (GFR 15-29)

64
Q

Definition of Stage 5 CKD

A

Kidney failure with GFR < 15

Clinical Chemistry (35 decks)

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