Tubes & Venipuncture/Phlebotomy

Question 1

SST (serum separator tubes)

Answer 1

Contain a gel that localizes between packed cells and the top serum layer (during centrifugation)

Used for routine assays. Not for therapeutic monitoring (As gel can absorb drugs), endocrine or immunologic testing/serology (interference of gel)

Question 2

Effects of prolonged tourniquet application

Answer 2

Hemoconcentration&raquo_space; increase in protein, iron, lipid, cholesterol

Anaerobic glyoclysis > lactate and decrease in pH

Question 3

Optical interference in spectrophotometric analysis

Answer 3

High light absorbence: Bilirubin (b/w 340 and 500 nm) and hemoglobin (Soret band; 412 nm)

Scattering light: lipid (can be reduced by ultracentrifugation)

Question 4

Grey top tube

Answer 4

Contain preservative sodium-fluoride, to prevent glycolysis (but not the glycolysis caused by septicemia)

For glucose measurement; especially in outpatient setting (where many hours may pass between sample collection and analysis)

An additional sample (in either gold or red top tubes) must be collected at the same time to run a BMP