Labatory Testing

Question 1

What does whole blood consist of?

Answer 1

Blood cells, suspected in a fluid component (plasma)
○ Blood cell components are leukocytes (white blood cells), erythrocytes (red blood cells),
and thrombocytes (platelets).

Question 2

What is plasma?

Answer 2

• The fluid part of the whole blood
• Plasma is about 90% water and 10% proteins, carbs, vitamins, hormones, fats, salts, enzymes, and wastes.

Question 3

What is Serum?

Answer 3

Plasma that has had fibrinogen removed

Question 4

What are purple/lavender-top tubes used for? How do they work?

Answer 4

Contains EDTA as the anticoagulant. It prevents coagulation by binding to calcium ions (calcium
is required for clotting)

Uses:
1. Complete blood count (CBC), hematocrit/packed cell volume, reticulocyte count (immature erythrocytes)
2. Collecting fluid that may clot from body cavities in which cell counts need to be performed. This may include cerebrospinal fluid, peritoneal or pleural effusions, + synovial fluid

Question 5

What are plain Red-Top Tubes used for>

Answer 5

Glass tubes have no additive; plastic tubes have clot activators
- Red-Top Tubes are used in immunology and in some serologic tests.
- These can also be used as a sterile tube for collecting samples for culture such as urine.

Question 6

What are Tiger-Top tubes used for? How do they work?

Answer 6

Serum separator tubes - contain a clot activator + gel for serum separation

Used for:
- Chemistry panels + are used to check any laboratory value seen on these panels + other tests requiring a serum sample
- These tubes are used for the majority of blood tests (BUN, creatinine, ALT, ALP, triglycerides, cholesterol, electrolytes, etc.)

Question 7

What are Blue-Top tubes used for? How do they work?

Answer 7

• Contains sodium citrate, an anticoagulant that binds calcium in the blood
• For accuracy, these tubes must be completely filled to recommended level
  
  • The appropriate ratio is 9 parts blood to 1 part citrate.
• Used to check for coagulation disorders: Prothrombin time (PT), Partial Thromboplastin Time
  (PTT), Fibrin Degradation Products (FDP), D-dimer, von Willebrand Factor, and other factor + fibrinolysis assays

Question 8

What are Green-Top tubes used for? How do they work?

Answer 8

• Plasma separator tubes (PST) - contain heparin
  - Heparin activates antithrombins, which block coagulation.
• Produces a whole blood/plasma sample and is used for collecting a plasma sample.

Question 9

What are Gray-Top tubes used for? How do they work?

Answer 9

• These tubes contain sodium fluoride, which is best known as a glucose preservative, + some contain potassium oxalate

Used if an accurate glucose measurement is needed and sample processing will be delayed.
- A blood glucose tested from serum in a red- or tiger-top tube in a delayed sample will be falsely low due to ongoing glucose metabolism by red blood cells in the tube