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CC 1 > 4.3 CARBS - LABORATORY METHODS > Flashcards

4.3 CARBS - LABORATORY METHODS Flashcards

1
Q

What is the most commonly used specimen for glucose testing?

A

Serum or plasma

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2
Q

What specimens can be considered for glucose testing

A

Whole blood,
plasma,
serum,
cerebrospinal fluid,
pleural fluid, and
urine

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3
Q

What is the standard clinical specimen for glucose testing, and which additive is commonly used?

A

Venous plasma with sodium fluoride as an additive.

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4
Q

What color is the stopper of the tubes containing sodium fluoride for glucose testing?

A

Gray

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5
Q

What type of blood is used in Point-of-Care Testing (POCT) for glucose levels?

A

Capillary blood.

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6
Q

By how much is the glucose concentration in whole blood lower than in plasma?

A

10% - 15% lower.

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7
Q

At what rate is glucose metabolized at room temperature in a blood sample?

A

7 mg/dL/hour (0.4 mmol/L/hour).

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8
Q

How much does glucose decrease per hour when a blood sample is stored at 4°C?

A

2 mg/dL/hour (0.1 mmol/L/hour).

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9
Q

What is the conversion factor for glucose from mg/dL to mmol/L?

A

0.0555.

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10
Q

How long should a serum specimen be separated from the cells to avoid glycolysis according to Henry’s 21st edition?

A

30 minutes.

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11
Q

How long does sodium fluoride prevent glycolysis in whole blood when refrigerated?

A

Up to 48 hours.

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12
Q

What is the recommended fasting period for obtaining a fasting blood glucose (FBG) sample?

A

8 to 10 hours (not longer than 16 hours).

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13
Q

When is fasting plasma glucose (FPG) typically higher, morning or afternoon?

A

FPG is higher in the morning.

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14
Q

It uses a strip; after capillary puncture, blood flows into the filter paper impregnated with reagent. The strip is then inserted into the glucometer, and the result appears after a few minutes.

A

glucometer

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15
Q

What can be added to a sample if it is not separated from the cells within 30 minutes?

A

Sodium fluoride.

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16
Q

How long should a serum specimen be separated from cells according to Bishop?

A

1 hour.

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17
Q

How long can sodium fluoride prevent glycolysis in whole blood when refrigerated?

A

Up to 48 hours.

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18
Q

What is the screening test for diabetes mellitus that is taken after at least 8 hours of fasting?

A

Fasting Blood Sugar (FBS) or Fasting Blood Glucose.

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19
Q

It indicates a prediabetic state and increased risk of developing diabetes, but it is not a clinical entity.

A

impaired fasting glucose

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20
Q

What type of test uses whole blood in EDTA and provides a picture of a patient’s blood glucose levels over the past three months?

A

Hemoglobin A1c (HbA1c).

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21
Q

What is the reference range for a normal Hemoglobin A1c (HbA1c) level?

A

4% - 6% (Henry’s 21st edition).

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22
Q

What HbA1c range indicates an increased risk for diabetes?

A

5.7% - 6.4%

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23
Q

At what HbA1c level is diabetes diagnosed?

A

≥ 6.5%.

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24
Q

What test is also known as glycosylated albumin or glycated albumin and monitors glucose control over the previous 3-6 weeks?

A

Fructosamine test.

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25
Q

What is the reference value for the Fructosamine test?

A

205 - 285 µmol/L.

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26
Q

What type of glucose test is randomly collected?

A

Random Blood Sugar (RBS).

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27
Q

In the 2-Hour Post Prandial Blood Sugar (PPBS) test, how much glucose is administered, and when is the sample drawn?

A

75g of glucose is administered, and the sample is drawn 2 hours after consumption of food

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28
Q

What are the two types of Glucose Tolerance Tests (GTT)?

A

Oral Glucose Tolerance Test (OGTT) and Intravenous Glucose Tolerance Test (IVGTT).

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29
Q

What type of GTT is performed for patients with malabsorption syndrome who cannot consume the glucose load?

A

Intravenous Glucose Tolerance Test (IVGTT).

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30
Q

How should a patient prepare for an Oral Glucose Tolerance Test (OGTT)?

A

The patient should consume 150g of carbohydrates per day for 3 days, discontinue medications affecting glucose tolerance, fast for 8-10 hours, and avoid excessive physical activity.

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31
Q

At what fasting blood glucose (FBG) level should an OGTT be terminated before giving the glucose load?

A

If FBG is greater than 140 mg/dL.

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32
Q

What is the glucose load for an adult in an OGTT?

A

75g of glucose dissolved in 300 mL of water.

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33
Q

What glucose dose is given to children in an OGTT?

A

1.75g of glucose per kilogram of body weight, up to a maximum of 75g.

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34
Q

What is the specimen required for the Hemoglobin A1c (HbA1c) test?

A

Whole blood in EDTA.

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35
Q

How does Hemoglobin A1c (HbA1c) relate to long-term glucose control?

A

It monitors long-term diabetes control over the previous 2-3 months.

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36
Q

For every 1% increase in HbA1c, how much does plasma glucose change?

A

A 1% increase in HbA1c corresponds to a 35 mg/dL (2 mmol/L) change in plasma glucose.

37
Q

What is the union or reaction involved in Hemoglobin A1c formation?

A

HbA1c is formed from the reaction between glucose and the hemoglobin protein, specifically the beta chain of hemoglobin.

38
Q

What is the reference value for Fructosamine?

A

205-285 µmol/L.

39
Q

What is the glucose specimen of choice for measuring glucose levels, and what additive is used?

A

Venous plasma is the standard clinical specimen, with sodium fluoride as the additive (gray stopper tubes).

40
Q

What is the glucose concentration difference between whole blood and plasma?

A

Glucose concentration in whole blood is 10%-15% lower than in plasma.

41
Q

What are the three types of ketones produced by the liver?

A

Acetone, 2%
acetoacetic acid, 20%
3-β-hydroxybutyric acid 78%

42
Q

What conditions can lead to increased ketone levels in the body?

A

Diabetes mellitus,
starvation/fasting,
high-fat diets,
prolonged vomiting,
glycogen storage disease

43
Q

What specimen types are used to detect ketones?

A

Fresh serum or urine

44
Q

hat is the accumulation of ketones in the blood called?

A

Ketonemia

45
Q

What is the accumulation of ketones in urine called?

A

Ketonuria

46
Q

Which test uses ferric chloride to detect acetoacetic acid and produces a red color?

A

Gerhardt’s test

47
Q

Which test uses sodium nitroprusside to detect acetoacetic acid and produces a purple color?

A

Sodium nitroprusside test

48
Q

Which enzymatic test detects 3-β-hydroxybutyric acid or acetoacetic acid?

A

3-hydroxybutyrate dehydrogenase test

49
Q

What is defined as persistent albuminuria in two out of three urine collections, with values between 30-300 mg/24h?

A

Microalbuminuria

50
Q

What ratio establishes clinical proteinuria or macroalbuminuria?

A

Albumin–creatinine ratio ≥ 300 mg/24 h or ≥ 300 μg/mg creatinine

51
Q

What collection methods are used for microalbuminuria testing?

A

Random spot collection, 24-hour collection, timed 4-hour overnight collection

52
Q

What is the normal fasting plasma glucose (FPG) range in mg/dL?

A

70-99 mg/dL

53
Q

What is the normal fasting plasma glucose (FPG) range in mmol/L?

A

3.9-5.5 mmol/L

54
Q

What is the impaired fasting glucose (FPG) range in mg/dL?

A

100-125 mg/dL

55
Q

What is the impaired fasting glucose (FPG) range in mmol/L?

A

5.6-6.9 mmol/L

56
Q

What FPG level in mg/dL indicates a provisional diabetes diagnosis?

A

≥ 126 mg/dL

57
Q

What FPG level in mmol/L indicates a provisional diabetes diagnosis?

A

≥ 7.0 mmol/L

58
Q

What is the normal two-hour plasma glucose (PG) range in mg/dL?

A

Answer: ≤ 140 mg/dL

59
Q

What is the normal two-hour plasma glucose (PG) range in mmol/L?

A

≤ 7.8 mmol/L

60
Q

What is the impaired glucose tolerance (IGT) range in mg/dL for a two-hour plasma glucose test?

A

140-199 mg/dL

61
Q

What is the impaired glucose tolerance (IGT) range in mmol/L for a two-hour plasma glucose test?

A

7.8-11.1 mmol/L

62
Q

What two-hour PG level in mg/dL indicates a provisional diabetes diagnosis?

A

≥ 200 mg/dL

63
Q

What two-hour PG level in mmol/L indicates a provisional diabetes diagnosis?

A

≥ 11.1 mmol/L

64
Q

methods for glucose determinatio

A

chemical
-oxidation reduction
-condensation

enzymatic
-glucose dehydrogenase
-glucose oxidase
-hexokinase method

65
Q

OXIDATION REDUCTION METHODS

A

Alkaline Copper Reduction Method
Alkaline Ferric Reduction Method (Hagedorn Jensen)

66
Q

Alkaline Copper Reduction Methods

A

Folin Wu Method
Nelson Somogyi Method
Neocuprein Method
Benedict’s Method
(Modification of FolinWu)

67
Q

Alkaline Copper Reduction Method
Principle

A

Reduction of cupric ions to cuprous ions forming cuprous oxide in hot alkaline solution by glucose.

68
Q

In the Folin Wu method, what does cuprous oxide react with to produce phosphomolybdenum blue?

A

Phosphomolybdate

69
Q

What does cuprous oxide react with in the Nelson-Somogyi method to form arsenomolybdenum blue?

A

Arsenomolybdate

70
Q

What reagent is used in the Neocuprein Method to detect glucose, and what color complex is produced?

A

2,9-Dimethyl-1,10-Phenantroline Hydrochloride; yellow or yellow-orange complex

71
Q

What is the purpose of Benedict’s Method, and what stabilizing agent does it use?

A

Detection and quantitation of reducing substances in body fluids; citrate or tartrate as a stabilizing agent

72
Q

What does copper sulfate react with in Benedict’s Method, and what precipitate is formed?

A

Glucose under heat; brick red precipitate

73
Q

What is reduced in the Alkaline Ferric Reduction Method (Hagedorn Jensen) for glucose measurement?

A

Ferricyanide is reduced to ferrocyanide.

74
Q

What type of colorimetry is used in the Hagedorn Jensen method, and what is the nature of the end product?

A

Inverse colorimetry; the end product is colorless.

75
Q

What is the name of the condensation method used for glucose measurement?

A

Ortho-toluidine (Dubowski Method)

76
Q

What is the end product of the Ortho-toluidine (Dubowski Method)?

A

Green-colored end product

77
Q

How do we produce the green colored end product in ortho toluidine

A

Glucose + Aromatic amines (with Glacial Hac and Heat) —> Glycosylamine + Schiff’s base

78
Q

What enzymes are involved in the Glucose Dehydrogenase method?

A

Mutarotase, Glucose Dehydrogenase, Diaphorase

79
Q

What does Mutarotase do in the Glucose Dehydrogenase method?

A

Converts α-D-glucose to β-D-glucose

80
Q

What reaction does Glucose Dehydrogenase catalyze in the Glucose Dehydrogenase method?

A

Converts β-D-glucose + NAD to D-gluconolactone + NADH

81
Q

What is the role of Diaphorase in the Glucose Dehydrogenase method?

A

Converts MTT + NADH to MTTH (blue color) + NAD

82
Q

What is the significance of NADH in the Glucose Dehydrogenase method?

A

NADH produced is proportional to glucose concentration

83
Q

Which method for glucose measurement can result in falsely decreased values due to uric acid, bilirubin, and ascorbic acid?

A

Glucose Oxidase method

84
Q

What substance can cause falsely increased glucose values in the Glucose Oxidase method?

A

Bleach

85
Q

Which chromogens are used in the Colorimetric Glucose Oxidase (Saifer-Gernstenfield) method?

A

3-methyl-2-benzothiazolinone hydrazone and N,N-dimethylaniline

86
Q

What does the Polarographic Glucose Oxidase method measure?

A

The rate of oxygen consumption proportional to glucose concentration

87
Q

Which glucose measurement method is considered the most specific?

A

Hexokinase method

88
Q

What wavelength is used to measure NADPH in the Hexokinase method?

A

340 nm

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