Phlebotomy and Body Fluid Preservation

Introduction to Phlebotomy and Body Fluid Preservation

• The sampling of body fluids and their preservation is discussed.
• Dr. Ross Pallett, a HCPC Biomedical Scientist (BS71638), is associated with this topic. His email address is provided: [email protected].

Preparation for the Lecture

• Reflect on phlebotomy experiences.
• Bring a cup of tea and biscuit.

Aim and Objectives

• The lecture aims to introduce phlebotomy and the preservation of body fluids.
• Topics covered include: reasons for sampling, the sample pathway, phlebotomy procedures, specimen tubes, order of draw, and auditing.

Why Sample Body Fluids?

• Diagnosis is a main reason for sampling.
• Monitoring treatment effectiveness is another.
• Compliance with treatment plans is a further motive.
• Prognosis (predicting future health) is also a factor.

Biomedical Scientists

• Biomedical Scientists perform 150 million samples annually.
• They are involved in 70% of all diagnoses.
• They function 24/7/365.
• Latest technology is used, such as the Abbott RealTime SARS-CoV-2 Amplification Reagent Kit.

Pathology: A History

• Key historical perspectives on pathology are explored, focusing on how the five senses (sight, touch, hearing, smell, and taste) were used in medical assessment in the past.
• Early approaches, including the four humours theory of the Ancient Greeks, are highlighted.
• Landmark figures (like William Harvey) and historical advancements are explained.
• The correlation between blood values and physiological conditions (as seen in the 19th century, thanks to Florence Nightingale and Joseph Lister) is referenced in the discussion.

Sample Pathway

• The sample pathway consists of three phases: - Pre-Analytical: Collection, labeling, and transport of the sample. - Analytical: Diagnostic testing. - Post-Analytical: Reports and sample storage.

Common Phlebotomy Sites

• The lecture mentions these sites for blood draws:
  • Median cubital vein
  • Cephalic vein
  • Back of the hand
  • Finger prick
  • Heel prick

Phlebotomy Supplies

• Vacuum-filled tubes, adapter, gloves, tourniquet, alcohol wipes, adhesive tape, gauze, and sharps bins are required for phlebotomy.
• Note that different sample collection requirements exist (some samples need to be sent on ice, protected from light, etc.) depending on the test involved.

Correct and Incorrect Sampling

• Demonstrations of correct and incorrect sampling techniques are shown.

Number of Medical Biochemistry Tests

• A table shows the rate/frequency of different tests per day:
  • Blood testing: 4,500 per day
  • Urine testing: 200 per day
  • Stool: 30 per day
  • Cerebrospinal Fluid (CSF), Drainage Fluids, Ascitic/Pleural Fluids, Stones (5-10, 5, 5-10, or 1 per two weeks).

Sample Collection Procedure

• Important steps of collecting samples are detailed: - Patient identification by name, date of birth, and ID. - The correct request form.

    - Selecting site and performing venipuncture, noting any bruising or other concerns.
    - Labeling procedure for samples, including matching to patient identifiers; adequate sample volume.
    - Proper tube selection and correct sample packaging (e.g., inverted tubes).
    - Prompt transport/correct storage considerations, e.g., whether the sample requires ice or protection from light; and what happens if it isn't received correctly.
    - Specific identifiers: full name, date of birth, and National Health Service (NHS) number  are required
  

Plasma vs. Serum

• Plasma is the cell-free liquid component of blood. Anti-coagulants are used
• Serum is plasma without clotting factors because it has been treated after coagulation.

Serum Separator Tube (SST)

• The yellow-top tube is a serum separator tube (SST).
• Inert gel is denser than serum but less dense than erythrocytes.
• It's coated with spray-coated silica particles.
• Routinely used for certain biochemistry tests (like U&E's, CRP, liver function, creatinine, lipid, and bone profiles).
• Invert the tube 5-6 times.
• Issues with incomplete barrier formation and damaged sampling probes are possible.
• Gel interference can occur in drug/endocrine tests.

Red Top Tube

• Red top tubes contain no additive.
• Serum is obtained from centrifugation.
• Alternative to yellow top where it is inappropriate.

Green Top Tube

• Two types of green top tubes (light and dark) exist. Light green tubes contain lithium heparin, an anticoagulant. The blood does not clot (plasma). Invert the tube 8-10 times. Dark green tubes have no gel, so the plasma needs to be separated by centrifugation. The dark green tubes are used to test for ammonia, insulin, and aluminum.

Purple Top Tube

• Anticoagulant: K-EDTA.
• Whole blood is collected.
• HbA1c (hemoglobin A1c) measures diabetes control.
• Used to assess Cyclosporin and Tacrolimus (anti-rejection drugs), and venous carboxyhemoglobin.
• Invert 8–10 times.

Light Grey Top Tube

• Anticoagulant: Potassium Oxalate.
• Sodium fluoride inhibits glycolysis for 5 days, and alcohol dehydrogenase.
• Contains glucose, and lactate.
• Invert 8-10 times.

Dark Blue Top Tube

• Purified glass, no contaminating trace metals.
• Used to test for copper, zinc, mercury, and selenium.

Order of Draw

• Yellow-top SST tubes must be drawn before other tubes.
• K-EDTA tubes are to follow.
• The risk of carryover must be addressed using this order.

Interference

• Haemolysed samples, icteric samples, and lipaemic samples need to be examined beforehand to avoid misleading analytical results. There are particular considerations related to potassium increases, phosphate, AST, LDH, Mg2+, bilirubin absorption, enzyme activity, and interference with common tests in blood sample analysis. Delays in separating plasma can also introduce errors (high K+, LDH). Incorrect sample containers can also lead to inaccurate glucose (no oxalate / fluoride).

Haemolysed Sample Audit

• Haemolysed samples lead to misleading results.
• Lab data shows issues, especially in A&E (24%).

Improvements

• Training for junior doctors, use of vacutainers, and order-of-draw instruction are recommended.

Sample Acceptance

• Criteria for sample acceptance, including the minimum number of matching identifiers, appropriate tubes, adequate volume, sample integrity, how rejected samples are reported.

Urines, Sweat

• Urine collection method and specific tests.
• Sweat chloride concentration and cystic fibrosis diagnosis.
• Cystic Fibrosis gene mutation screening considerations.

Summary

• The overall quality of the sample analysis is very important, and a proper pre-analytical process is essential.
• Using proper sample types and correct volume are critical.
• Proper sample integrity is essential.
• Minimum identification criteria and the importance of order of draw (avoiding carryover) are highlighted.
• Auditing completes the process.

This quiz covers key concepts in phlebotomy and the preservation of body fluids. Topics include sampling procedures, specimen handling, and the role of biomedical scientists in diagnostics. It's an essential resource for understanding how phlebotomy contributes to accurate health assessments.