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Clinical Chemistry (CC 1) > (F) L4: Renal Function (Part 2: Evaluation) > Flashcards

(F) L4: Renal Function (Part 2: Evaluation) Flashcards

1
Q

Tests for Renal Blood Flow

These 2 (main) NPN analytes, when elevated, may indicate a problem in the renal blood flow

A

Urea and Creatinine

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2
Q

Tests for Renal Blood Flow

TOF: NPNs are sensitive indicators for renal insufficiency

A

False (are NOT sensitive, before they can be detected as elevated in the serum, renal failure most likely has occurred)

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3
Q

Tests for GFR

  • This measures the clearance of normal molecules such as those that are filtered, not protein-bound, and those neither absorbed nor secreted by the glomerulus and tubules
  • An overall indicator of kidney function level
A

Glomerular Filtration Rate

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4
Q

Tests for GFR

  • Refers to the rate at which the kidneys are able to remove substances from the blood
  • The volume of plasma from which a measured amount of substance can be completely eliminated into the urine per unit of time
  • Expressed in mL/min
A

Clearance Tests

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5
Q

Tests for GFR

What are the 2 markers for clearance tests?

A
  1. Exogenous - administered
  2. Endogenous - naturally excreted from the patient’s body
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6
Q

Tests for GFR

If a marker can be reabsorbed, what does that mean for the urine sample?

A

False decreased (it returns to the blood, lowering the levels found in the kidney)

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7
Q

Tests for GFR

If a marker can be secreted, what does that mean for the urine sample?

A

False increased (it oversaturates the urine)

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8
Q

Tests for GFR

Underestimating the GFR
A. Reabsorption
B. Secretion
C. Both
D. Neither

A

A. Reabsorption

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9
Q

Tests for GFR

Overestimating the GFR
A. Reabsorption
B. Secretion
C. Both
D. Neither

A

B. Secretion

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10
Q

Tests for GFR

What does a high clearance test result mean in terms of efficiency of excretion?

A

Kidneys are efficient in excretion

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11
Q

Tests for GFR

What does a low clearance test result mean in terms of efficiency of excretion?

A

Kidneys are inefficient in excretion

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12
Q

Tests for GFR

What is the analyte?
Male reference value (conventional unit): 107-139 mL/min
Female reference value (conventional unit): 87-107 mL/min

A

Creatinine Clearance

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13
Q

Tests for GFR

What is the analyte?
Maximum clearance (conventional unit): 64-99 mL/min
Standard clearance (conventional unit): 41-65 mL/min or more than 75%

A

Urea Clearance

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14
Q

Tests for GFR

What is the analyte?
Conversion factor is 0.01667

A

Creatinine and Urea Clearance

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15
Q

Tests for GFR

What is the analyte?
Reference values (SI Unit): 1.78-2.34 mL/sec and 1.45-1.78 mL/sec

A

Creatinine Clearance

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16
Q

Tests for GFR

What is the analyte?
Reference values (SI Unit):
- 1.07-1.65 mL/sec
- 0.68-1.08 Ls
- More than 0.75 of normal clearance

A

Urea clearance

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17
Q

Tests for GFR (exogenous stubstance)

  • The reference/gold standard method
  • Substance is soluble, freely filtered, and neither secreted nor reabsorbed
  • Not routinely done due to the need for IV infusion
A

Inulin

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18
Q

Tests for GFR (exogenous stubstance)

Reference values:
Male: 127 mL/min/1.73 m2
Female: 118 mL/min/1.73m2

A

Inulin

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19
Q

Tests for GFR (exogenous stubstance)

  • 124 I-iothalamate and 99m Tc-DTPA
  • Iohexol and 51Cr-EDTA
A

Radioactive Markers

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20
Q

Tests for GFR

Give the 2 exogenous substances used

A
  1. Inulin
  2. Radioactive Markers
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21
Q

Tests for GFR (endogenous substances)

  • Measures 113 Daltons
  • Requires a 24-hr time frame
  • The most widely used marker
  • Is produced constantly, not bound to proteins, not reabsorbed, BUT minimally secreted by the tubules
A

Creatinine Clearance

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22
Q

Tests for GFR (endogenous substances)

TOF: In creatinine clearance, there is an overestimation of GFR (false increase)

A

True (because it is MINIMALLY secreted)

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23
Q

Tests for GFR (endogenous substances)

This modification takes into account the disadvantage of creatinine being minimally secreted by the tubules (it inhibits secretion)

A

Cimetidine-enhanced Creatinine Clearance

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24
Q

Tests for GFR (endogenous substances)

Drawbacks of this test method:
- Ingestion of meat
- Interference with the colorimetric method
- Is partially secreted by the tubules

A

Creatinine Clearance

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25
Q

Tests for GFR (endogenous substances)

Reference values of this method:
Male: 85-125 mL/min
Female: 75-112 mL/min

A

Creatinine Clearance

26
Q

Tests for GFR (endogenous substances)

Give the 5 formulas for estimating creatinine clearance as an estimate for GFR

A
  1. Cockcroft-Gault
  2. Modification of Diet in Renal Disease (MDRD) or the Levy Formula
  3. Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI)
  4. Schwartz
  5. Counahan-Barrett
27
Q

Tests for GFR (endogenous substances)

5 formulas for estimating creatinine clearance as an estimate for GFR:

  • Takes into account age, mass (in kg), and serum creatinine
  • If the patient is female, multiply to 0.85 (due to less muscle mass)
A

Cockcroft-Gault

28
Q

Tests for GFR (endogenous substances)

5 formulas for estimating creatinine clearance as an estimate for GFR:

  • Takes into account age, sex, race, serum creatinine, BUN, and albumin
  • The simplified version of this only takes into account age, sex, race, and serum creatinine (4 variables)
A

Modification of Diet in Renal Disease (MDRD) or the Levy Formula

29
Q

Tests for GFR (endogenous substances)

5 formulas for estimating creatinine clearance as an estimate for GFR:

Used for children

A

Schwartz and Counahan-Barrett

29
Q

Tests for GFR (endogenous substances)

5 formulas for estimating creatinine clearance as an estimate for GFR:

More accurate than MDRD in estimating GFR especially for patients with stage 1-3 kidney disease

A

Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI)

30
Q

Tests for GFR (endogenous substances)

Was historically used to measure GFR but since it is reabsorbed by the tubules (around 40-45% of it), it is not anymore

31
Q

Tests for GFR (endogenous substances)

TOF: In urea clearance, there is an overestimation of GFR (false increase)

A

False (under estimation; false decrease)

Due to 40-45% of urea being reabsorbed

32
Q

Tests for GFR (endogenous substances)

  • This makes up over 45% of NPNs
  • Is a better indicator for nitrogen intake and state of hydration than GFR
  • Is freely filtered but variably reabsorbed
A

Urea Clearance

33
Q

Tests for GFR (endogenous substances)

  • A GFR test but not considered a clearance test as it is not measured in the urine but rather in the serum
  • It is broken down and reabsorbed by the PCT
  • A small protein produced by nucleated cells and is freely filtered
  • Unaffected by age, gender, race, and muscle mass
A

Cystatin C

34
Q

Tests for GFR (endogenous substances)

If Cystatin C is increased in serum, what will happen to its levels in the urine?

35
Q

Tests for GFR (endogenous substances)

These substances reduce the production of Cystatin C

A

Glucocorticoids

36
Q

Tests for GFR (endogenous substances)

  • A GFR test but not a clearance test
  • Is freely filtered but completely reabsorbed and broken down in the PCT hence measured in the serum
  • An increase of this denotes renal disease
A

B-Trace Protein

37
Q

Tests for GFR (endogenous substances)

  • A GFR test but not a clearance test
  • Is freely filtered but completely reabsorbed and broken down in the PCT hence measured in the serum
  • It assesses renal tubular function in renal transplant patients
  • Elevated levels indicate organ rejection
A

B2-Microglobulin

38
Q

Tests for GFR (endogenous substances)

  • Is present in all nucleated cells
  • A component of Type 1 MHC
  • If increased, it denotes incompatibility between the donor’s organ and the recipient’s body
A

B2-Microglobulin

39
Q

Tests for GFR (endogenous substances)

  • Mannopyranosyl-I-tryptophan (MPT) is produced in the body by the glycoconjugation of tryptophan
  • Is freely filtered and not reabsorbed
  • Not affected by muscle mass
  • Only measured by HPLC hence time consuming and expensive
A

Tryptophan Glycoconjugate

40
Q

Give the 6 analytes measured for Renal Blood Flow

A
  1. Urea
  2. Creatinine
  3. Uric Acid
  4. Amino Acids
  5. Creatine
  6. Ammonia
41
Q

Give the endogenous substances/methods for the measurement of GFR

A
  1. Creatinine Clearance
  2. Urea Clearance
  3. Cystatin C
  4. B-Trace Protein
  5. B2-Microglobulin
  6. Tryptophan Glycoconjugate
42
Q

Completely reabsorbed and broken down by the DCT
A. Cystatin C
B. B-Trace Protein
C. B2-Microglobulin
D. Both
E. Neither

A

D. Neither (should be PCT)

43
Q

Freely filtered and not reabsorbed
A. Tryptophan Glycoconjugate
B. Creatinine Clearance
C. Both
D. Neither

44
Q

Give the 2 tests for tubular reabsorption

A
  1. Specific Gravity
  2. Osmolality
45
Q

Tests for Tubular Reabsorption

  • Compares the weight of fluid to that of distilled water at a reference temperature
  • Affected by the number and mass of solutes
A

Specific Gravity

46
Q

Tests for Tubular Reabsorption (SG Methods)

  • Patients are deprived of fluids for 24 hours prior to measurement
  • Normal result: Kidneys will reabsorb water and urine becomes concentrated (SG increases)
A

Fishberg Test

47
Q

Tests for Tubular Reabsorption (SG Methods)

  • It compares the volume and specific gravity of day and night samples
  • Reference value: 1.005-1.030
A

Mosenthal Test

48
Q

Tests for Tubular Reabsorption

  • More accurate/specific in assessing the concentrating ability of the tubules
  • An expression of concentration in terms of the total number of solutes present per kg of solvent
  • It is ONLY affected by the number of solutes and not the mass of it
A

Osmolality

49
Q

Tests for Tubular Reabsorption

TOF: Urine osmolality is due to urea and plasma osmolality which is due to potassium and chlorine

A

False (SODIUM and chloride)

50
Q

Tests for Tubular Reabsorption (Osmolality)

Give the 2 direct methods

A
  1. Freezing Point Osmometer
  2. Vapor Pressure Osmometer
51
Q

Tests for Tubular Reabsorption (Direct Osmolality)

Which is the more popular method among the two and which uses the Seebeck effect?

A. Vapor Pressure Osmometer
B. Freezing Point Osmometer

A
  1. More popular - Freezing Point
  2. Seebeck effect - Vapor Pressure
52
Q

Tests for Tubular Reabsorption (Direct Osmolality)

  1. An increased osmolality causes a/an (decrease/increase) in both freezing point and vapor pressure
  2. An increased osmolality causes a/an (decrease/increase) in both boiling point and osmotic pressure
A
  1. Decrease
  2. Increase
53
Q

Tests for Tubular Reabsorption (Direct Osmolality)

What are the 3 factors needed to compute for serum osmolality?

A
  1. Sodium
  2. Glucose
  3. BUN
54
Q

Give the 3 tests for tubular secretion

A
  1. P-aminohippuric Tests (PAH Test)
  2. Phenolsulfonpthalein Dye Test
  3. Titratable Acidity and Urinary Ammonia
55
Q

Tests for Tubular Secretion

  • Also measures renal blood flow by using the clearance of a dye
  • The volume of plasma flowing through the kidneys determines the amount of this substance in the urine
  • An obsolete method due to the administration of dye and difficulty to interpret
  • Reference value
A

P-Aminohippuric Tests (PAH Test)

56
Q

Tests for Tubular Secretion

Reference value of 600-700 mL/min

A

P-Aminohippuric Tests (PAH Test)

57
Q

Tests for Tubular Secretion

  • Measures the excretion of dye proportional to the renal tubular mass
  • An obsolete method due to the administration of dye and difficulty to interpret
A

Phenolsulfonphthalein Dye Test

58
Q

Tests for Tubular Secretion

Reference value: 1,200 mL of blood flow/min.

A

Phenolsulfonphthalein Dye Test

59
Q

Tests for Tubular Secretion

An obsolete method due to the administration of dye and difficulty to interpret
A. P-Aminohippuric Test (PAH Test)
B. Titratable Acidity and Urinary Ammonia
C. Phenolsulfonphthalein Dye Test
D. A and B
E. B and C
F. A and C

A

F. A and C

60
Q

Tests for Tubular Secretion

Since the function of the kidneys in the acid-base balance is to secrete hydrogen ions for the secretion of acids, this is the only way to measure tubular secretion in that aspect

A

Titratable Acidity and Urinary Ammonia

Clinical Chemistry (CC 1) (33 decks)

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