Lab Medicine 4

Question 1

Diurnal Variation in tests

Answer 1

• Time of day, month or year may affect lab test results explain:
• Some tests must be collected at specific times or days in order to provide meaningful clinical information.

Question 2

Examples of diurnal variation in tests

Answer 2

Question 3

What are adrenal disorders?

Answer 3

• Hyperfunction: Cushing syndrome.
• Hypofunction: Adrenal insufficiency.

Question 4

Answer 4

Question 5

Levels of cortisol And ACTH in blood

Answer 5

• Cortisol & ACTH levels fluctuate throughout the day

Peak levels: In the early morning.

Lowest levels in the late evening around bedtime.

Question 6

sample collection for cortisol

Answer 6

We collect 2 samples:

• 1st sample: At 8:00 AM.
• 2nd sample: At 8:00 PM “in the same day”

Question 7

Serum cortisol levels & salivary cortisol in late night

Answer 7

Elevated

Question 8

Besides time, name other biologic variables that may affect test results of cortisol

Answer 8

1. Age.
2. Gender.
3. Race.
4. Exercise.
5. Diet.
6. Posture.
7. Stress (venipuncture).
8. Genetic predisposition.

Question 9

Tests to diagnose adrenal insufficiency

Answer 9

• Basic chemistry profile.
• CBC (Complete Blood Count).
• Urinalysis.

Question 10

Answer 10

Question 11

Other Variables affecting cortisol and ACTH testing

Answer 11

• Emotional stress.
• Estrogens containing oral contraceptive.
• Steroid therapy:
• Stopped within 12 h before the test.
• If not possible (as in Addison disease dexamethasone should be prescribed (As it doesn’t cross react with cortisol assay) & not-prednisolone.

Question 12

Time of sample collection for cortisol & ACTH

Answer 12

• 2 Samples (because of daily circadian rhythm).
• Morning: 8 - 10 AM.
• Evening: 10 - 12 PM.

Question 13

Time of sample collection for Sex hormones & Gonadotropins

Answer 13

Monthly circadian rhythm in female.

Question 14

Blood sample Collection

• Additive on sample
• Test done on

Answer 14

Question 15

insulin sample collecion

Answer 15

separated immediately and kept in fridge

Question 16

Def of Competitive binding techniques

Answer 16

The method where the hormone competes with labelled one for binding sites in vitro.

Question 17

Binding sites in Competitive binding techniques

Answer 17

1. Antibody.
2. Binding proteins.
3. Receptor.

Question 18

Labelling in Competitive binding techniques

Answer 18

• Radioisotope.
• Enzymes.
• Fluorochrome.

Question 19

Examples of Competitive binding techniques

Answer 19

1. Radioimmunoassay (RIA)
2. Enzyme linked immunosorbent assay (ELISA)
3. Fluoro immunoassay (FIA)

Question 20

Chromatography

Answer 20

This is a reference method.

Question 21

Samples for Catecholeamines Testing

Answer 21

Blood & Urine

Question 22

Blood sample for Catecholeamines Testing

Answer 22

• Measurement of plasma catecholamines.
• A sensitive test that needs specialized equipment’s.

Question 23

Urine sample for Catecholeamines Testing

Answer 23

• The reliable test: Measurement of urinary vanillymandelic acid (VMA).
• VMA: Is the end stage metabolite of catecholamines,
  Excreted in urine.

Question 24

blood Sample collection for Catecholeamines Testing * In patients with paroxysmal attacks of hypertension

Answer 24

Basal measurements should be made once in between attacks & another estimation, when the next attack occurs.

Question 25

Cautions during collection & timing of urine specimens (24 hours) for VMA for catecholeamines testing

Answer 25

The diet excluded the following Items:
1. Caffeine as in (coffee - tea - cocoa - chocolate)

2. Amines as in (bananas - walnuts - avocados - fava beans - cheese - beer * red wine).
3. Vanilla (in foods or fluids)
4. Licorice
5. Nicotine (4 hours before collection of urine and during the urine collection),
6. Alcohol (ethanol) & cocaine.
7. These analytes are sensitive to drugs (azathloprine).