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AUBF > 4.4 GLUCOSE > Flashcards

4.4 GLUCOSE Flashcards

1
Q

What is the most frequently performed chemical analysis on urine?

A

Glucose test

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2
Q

Why is glucose testing included in physical examinations and health screening programs?

A

To detect and monitor diabetes mellitus and because many cases remain undiagnosed without testing.

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3
Q

What is the renal threshold for glucose reabsorption in the blood?

A

Approximately 160 to 180 mg/dL.

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4
Q

When is the most informative time to collect urine specimens for glucose testing?

A

After fasting or 2 hours after meals

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5
Q

What condition occurs during pregnancy due to placental hormones blocking insulin action?

A

Gestational diabetes

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6
Q

What complications can arise for the baby from gestational diabetes?

A

Macrosomia, obesity, and increased risk of type 2 diabetes later in life.

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7
Q

Name a condition where glucose appears in urine without hyperglycemia.

A

Renal glycosuria

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8
Q

What enzyme-based method is used in reagent strips for glucose testing?

A

Glucose oxidase method

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9
Q

What are the two steps in the glucose oxidase reaction for urine testing?

A
  1. Glucose reacts with oxygen to form gluconic acid and hydrogen peroxide.
  2. Hydrogen peroxide reacts with chromogen to produce a colored compound.
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10
Q

Name two chromogens used in glucose reagent strips.

A

Potassium iodide (Multistix) and tetramethylbenzidine (Chemstrip).

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11
Q

What can cause a false-positive reaction in glucose oxidase testing?

A

Contamination by oxidizing agents or detergents

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12
Q

What substances can interfere with the enzymatic reaction, causing false-negative results?

A

Ascorbic acid,
high levels of ketones,
high specific gravity, l
ow temperature, and
unpreserved specimens.

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13
Q

What is the principle of the Clinitest method for glucose detection?

A

Reduction of copper sulfate to cuprous oxide in the presence of heat and alkali

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14
Q

What phenomenon can occur at high glucose levels during the Clinitest reaction?

A

“Pass through” phenomenon

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15
Q

What is the clinical significance of galactose in urine?

A

It indicates galactosemia, an inborn error of metabolism caused by a deficiency of galactose-1-phosphate uridyl transferase (GALT).

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16
Q

Why is the Clinitest no longer recommended for newborn screening of galactosemia?

A

Because blood screening for GALT activity is more sensitive and specific.

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17
Q

What reducing sugars other than glucose can cause positive results in the Clinitest?

A

Galactose, lactose, fructose, maltose, and pentose.

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18
Q

What type of sugar is sucrose, and does it react with Clinitest or glucose oxidase strips?

A

Sucrose is a non-reducing sugar and does not react with these tests.

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19
Q

What precautions should be taken during the Clinitest procedure due to heat?

A

Use thick glass test tubes and avoid touching the bottom of the test tube

20
Q

What percentage of diabetes mellitus cases worldwide are undiagnosed?

A

Over 50%

21
Q

How can patients monitor their glucose levels at home?

A

Using reagent strip methods for blood and urine glucose testing

22
Q

What happens when blood glucose exceeds the renal threshold?

A

Glucose appears in urine (glycosuria).

23
Q

Why might a first-morning urine specimen not represent a fasting state for glucose testing?

A

Residual glucose from an evening meal may remain in the bladder overnight

24
Q

What conditions unrelated to diabetes can cause hyperglycemia and glycosuria?

A

Pancreatitis,
acromegaly,
Cushing syndrome,
hyperthyroidism,
pheochromocytoma,
thyrotoxicosis, and
severe stress.

25
Q

What hormones oppose insulin action and increase glucose levels?

A

Glucagon, epinephrine, cortisol, thyroxine, and growth hormone.

26
Q

What is the role of insulin in glucose regulation?

A

Insulin converts glucose to glycogen for storage (glycogenesis).

27
Q

What condition is caused by compromised renal tubule glucose reabsorption?

A

Renal glycosuria

28
Q

What are examples of diseases associated with renal glycosuria?

A

End-stage renal disease, cystinosis, and Fanconi syndrome.

29
Q

What is the sensitivity range for glucose detection in Multistix and Chemstrip reagent strips?

A

Multistix: 75 to 125 mg/dL; Chemstrip: 40 mg/dL

30
Q

What reagent is used in Clinitest tablets to prevent interference from room air?

A

Sodium carbonate releases carbon dioxide during the reaction

31
Q

Why must Clinitest reactions be closely observed?

A

To avoid missing the “pass through” phenomenon.

32
Q

What is the minimum sensitivity of Clinitest for glucose detection?

A

200 mg/dL

33
Q

What common laboratory substances can interfere with Clinitest results?

A

Drug metabolites, antibiotics like cephalosporins, and ascorbic acid.

34
Q

How should Clinitest tablets be stored to prevent degradation?

A

In tightly closed packages to avoid moisture.

35
Q

What does a strong blue color in unused Clinitest tablets indicate?

A

Deterioration due to moisture

36
Q

What is a key safety precaution when performing the Clinitest procedure?

A

Use a heat-resistant rack and thick glass test tubes to avoid burns.

37
Q

What are the steps in performing the Clinitest using the five-drop method?

A

Place a thick glass test tube in a rack.
Add five drops of urine.
Add 10 drops of distilled water.
Drop one Clinitest tablet and observe until reaction ceases.
Wait 15 seconds, shake gently, and compare color to the chart.

38
Q

How is galactosemia detected in newborns today?

A

Through blood screening for galactose-1-phosphate uridyl transferase (GALT) activity

39
Q

What specimen collection condition provides the most informative glucose results?

A

Specimens collected under controlled conditions, such as fasting or 2 hours post-meal

40
Q

Why is detection of gestational diabetes important for the baby?

A

High maternal glucose crosses the placenta, causing fetal hyperglycemia and macrosomia.

41
Q

What are potential long-term risks for babies born to mothers with gestational diabetes?

A

Obesity and type 2 diabetes later in life.

42
Q

What condition may cause glycosuria during pregnancy apart from gestational diabetes?

A

Temporary lowering of the renal glucose threshold

43
Q

What causes false-positive glucose oxidase test results?

A

Contamination with peroxide or strong oxidizing detergents.

44
Q

How do reagent strip manufacturers minimize ascorbic acid interference?

A

By adding chemicals like iodate to oxidize ascorbic acid.

45
Q

What is the principle of the glucose oxidase test on reagent strips?

A

A double sequential enzyme reaction involving glucose oxidase and peroxidase

46
Q

What is the principle behind the copper reduction test in Clinitest?

A

Reducing substances convert copper sulfate (blue) to cuprous oxide (orange/red) in the presence of alkali and heat

47
Q
A

AUBF (17 decks)

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