Clinical Specimens: Blood Analysis

Clinical Specimens

• CLS 251, Lecture 3, by Mohammad A. Alfhili, Ph.D.

Outline

• For each body fluid, understand:

  • Physiology (how it's formed and its role)
  • Collection methods
  • Storage/disposal procedures in the lab

• List of body fluids discussed:

  • Blood

Blood

• Constituents:

  • Plasma (55%): Water, ions (sodium, potassium, calcium, etc.), bicarbonate, plasma proteins (albumin, fibrinogen, immunoglobulins), antibodies, substances transported by blood (nutrients, waste products, respiratory gases, hormones).

  • Cellular elements (45%):

    • Erythrocytes (red blood cells): 5-6 million per mm³ - Transport oxygen and CO2.
    • Leukocytes (white blood cells): 5,000-10,000 per mm³ - Defense and immunity (basophils, lymphocytes, eosinophils, neutrophils, monocytes).
    • Platelets: 250,000-400,000 per mm³ - Blood clotting

• Functions: Plasma is the liquid portion, maintaining osmotic balance, pH buffering, and regulating membrane permeability. Cellular components have roles in oxygen and CO2 transport, defense, and clotting etc.

Plasma vs. Serum

• Plasma: Liquid portion of blood containing all coagulation factors and fibrinogen; additives interfere with results, giving hazy/yellow appearance, more protein (fibrinogen)

  • Requires immediate centrifugation

• Serum: Liquid portion formed after blood clots; no coagulation factors or fibrinogen; clearer, yellow appearance; more K+.

  • Requires 20 minutes for clot formation.

Phlebotomy

• Phlebotomy: blood collection procedure

  • Patient details (ID, diet, activity, tests required) are essential.
  • Isopropyl alcohol (70%) sterilizes collection site.

• Tourniquet placement : above puncture site, use other hand to stop IV, or avoid first 5mls if in direct line with IV.

• Venipuncture site: Pierce with bevel up at 45 degrees.

  • Avoid areas with scars, wounds, burns, hematomas, or edema.

  • Special consideration for infants (finger/heel sticks)

• Place gauze and bandage after needle removal.

  • Label tubes with patient details

• Appropriate vein: medial cubital vein is preferred due to size, location, and stability.

  • Avoid cephalic, median, and basilic veins due to tendency to bruise easily.

Evacuated/Vacuum Tubes

• Disposable double-pointed needle (one side plastic, one rubber) helps with insertion into vein (45° with bevel up)
• Removing tourniquet prevents hemoconcentration (high concentration of molecules like AST, iron, etc)
• Use of the other hand to fill vacutainer tubes
• Vacuum draws blood into tubes while the needle is in place
• Remove tube before withdrawing the needle.

Needle & Syringe

• Needle gauge (diameter) is critical for different procedures.
  • Large gauges (16) for blood donation
  • Standard gauges (21) for routine phlebotomy
  • Smaller gauges (23) for thin veins (increased risk for hemolysis)
• Syringes preferred for better control over suction and prevent spilling blood.

Phlebotomy Complications

• Syncope (fainting): Stop procedure immediately, lower patient, apply cool cloths, and offer fluids.
• Hematoma (blood collection under skin): Avoid excessive probing, excessive pressure, or failure to effectively apply pressure after removal. Apply firm pressure for 2 mins.

Tubes (by color)

• Red Top (plain tubes): For chemistry, serology, and blood bank tests; blood clots naturally in about 60 minutes; cells are preserved for use -Not suitable for blood banking (presence of silica)
• Lavender (Purple Top): Useful for hematology, no clumping of platelets, compatible with staining. EDTA prevents clotting. -Avoid using for Chemistry or coagulation tests
• Light Blue Top: For coagulation tests. Sodium citrate binds to calcium to prevent clotting. (Blood/anticoagulant ratio is 9:1)
  -Lower citrate ratio may be necessary for patients with high hematocrit.
• Green Top: For chemistry (e.g., STAT electrolytes) and K+ testing. Heparin inhibits thrombin. -Often not suitable for hematology due to dark background -Li heparin often preferred for the best results.
• Gray Top: For chemistry requiring glucose and ethanol measurements; potassium oxalate or K2EDTA prevents clotting by binding to Calcium; not used often for hematology (destroys cellular morphology)
• White Top: For molecular diagnosis, chemistry, PCRs. (K2EDTA)
• Royal Blue Top: For toxicology, trace metals, and nutritional assessment. Often metal free.
• Yellow Top: Used for cell culture studies, blood bank tests (HLA phenotyping, paternity testing), or when the presence of sodium polyanetholesulfonate and acid citrate dextrose is desired.
• Gold/Red/Grey: (Serum separator tubes) For STAT chemistry (not TDM); clot activators (silica or celite) separate serum by centrifugation; not suitable for blood banking or serology, or if immune reactions are possible.
• Orange/Yellow/Grey: Used for STAT chemistry for patients on anticoagulant therapy; uses thrombin to effectively clot blood in 5 minutes.

Preservation of Specimens

• Refrigerated (4°C) up to 24 hours, or frozen (-20°C) for longer durations.
• Glass tubes should NOT be frozen.
• Long-term storage should prefer -80°C.

This quiz covers key concepts from CLS 251, Lecture 3, focusing on the physiology, collection methods, and storage of various body fluids, especially blood. You will learn about the constituents of blood, including plasma and cellular elements, and their functions. Test your understanding of blood sample management in a clinical laboratory setting.