MLS 123_05_Pre-Analytical

Principles of Medical Laboratory Science Practice

  • Lecture Instructor: Agabao, Princess Jonalyn, RMT

Pre-analytical Considerations in Phlebotomy

Module Objectives

  • After completing this module, be able to:

    1. Identify problem areas to avoid in site selection, with reasons for concern and procedures to follow when encountered.

    2. Explain handling patient complications related to blood collection.

    3. Explain how to avoid or manage procedural errors, including reasons for failure to draw blood.

    4. Discuss appropriate specimen quality.

Pre-analytical Phase

  • The preanalytical phase includes all actions prior to analysis, starting from a test order to the commencement of testing.

  • Neglecting this phase can compromise specimen quality, endanger patient health, and elevate medical costs.

Definition of Terms

Reference Range

  • Reference range: Values used for comparing a patient’s results; prior results may also be considered.

Basal State

  • Basal state: The body's resting metabolic state, early in the morning after fasting for approximately 12 hours. Ideal for establishing reference ranges.

Physiological Variables

Influencing Factors

  • Age: Blood component values vary with age (e.g., higher RBC and WBC values in newborns).

  • Altitude: Test results can vary significantly at high altitudes compared to sea level.

  • Dehydration: Results in hemoconcentration due to decreased body fluid from vomiting or diarrhea.

  • Diet: Ingestion of food and drink alters blood analyte composition. Blood draws should ideally occur after fasting for 8-12 hours to minimize dietary influences.

  • Diurnal/Circadian Variations: Many blood components exhibit daily variations (e.g., cortisol peaks at 8 AM).

  • Drug Therapy: Medications can alter physiological functions and analyte concentrations.

  • Exercise: Physical activity raises some blood component levels while lowering others.

  • Fever: Can disrupt normal levels of hormones and increase insulin.

  • Gender: Differences in blood component concentrations become apparent post-sexual maturity.

  • Intramuscular Injection: May elevate specific enzyme levels; collections should be timed appropriately.

  • Jaundice: Excess bilirubin affects blood color and can interfere with test results.

  • Positioning: Body position impacts blood fluid filtration and specimen composition, influencing laboratory outcomes.

  • Pregnancy: Leads to physiological changes, including increased body fluids that may dilute RBC counts.

  • Smoking: Influences multiple blood analyte levels, depending on frequency and quantity smoked.

  • Stress: Emotional responses can transiently elevate WBC counts.

  • Temperature and Humidity: External temperature affects blood fluid composition.

Problem Venipuncture Sites

Avoiding Certain Sites

  • Burns, scars, and tattoos should be avoided to prevent difficulties in palpation and potential contamination.

  • Damaged veins (sclerosed or thrombosed) may result from previous blood draws or medical conditions.

  • Edematous areas should not be used due to potential inaccuracies in test results.

  • Hematomas can interfere with blood flow and alter test results from contamination.

  • Obese patients may present challenges in locating veins, necessitating special techniques for successful draws.

  • Mastectomy: Venipuncture should not be performed on the same side without physician consultation due to risk of lymphostasis.

Complications and Management During Venipuncture

Allergies and Adverse Reactions

  • Be alert to patient allergies to equipment and supplies (e.g., latex, antiseptics).

Excessive Bleeding

  • Apply pressure to the site until bleeding stops; notify appropriate personnel if bleeding continues.

Fainting

  • Monitor patients for signs of fainting and ready to assist them as needed.

Nausea and Vomiting

  • Wait until nausea subsides before proceeding with blood draws.

Pain Management

  • Prepare the patient for minor pain; allow antiseptic to dry to minimize discomfort.

Petechiae

  • Observe for petechiae as possible indicators of excessive bleeding risk.

Seizures/Convulsion

  • Discontinue the draw and provide care if seizures occur; avoid inserting objects into the mouth.

Hematoma Formation

  • Manage hematomas promptly with pressure and ice; educate on causes to prevent recurrence.

Iatrogenic Anemia

  • Coordinate with physicians to minimize blood loss from frequent draws, especially in vulnerable populations.

Inadvertent Arterial Puncture

  • Recognize and manage potential arterial punctures appropriately, applying pressure as needed.

Infection Control

  • Observe aseptic techniques to minimize infection risk during venipuncture.

Nerve Injury

  • Recognize signs and manage as necessary to prevent lasting damage.

Reflux of Additives

  • Take precautions against reflux when drawing blood from lines to prevent contamination.

Vein Damage

  • Limit venipunctures in the same area over time to prevent tissue damage.

Quality of Blood Specimens

Hemoconcentration

  • Understand causes (like prolonged tourniquet use) leading to tests yielding inaccurate results.

Hemolysis

  • Identify and mitigate procedural errors that may result in hemolysis; effects on serum and plasma quality should be monitored.

Partially Filled Tubes

  • Ensure correct volume in tubes to avoid testing errors and compromised results.

Specimen Contamination

  • Maintain proper protocols to prevent accidental contamination that may interfere with test results.

Wrong or Expired Collection Tubes

  • Ensure tubes are the correct type and within expiration dates to avoid erroneous results.

Analytical and Post-analytical Considerations

Analytical Considerations

  • Follow tested protocols and manufacturer instructions to maintain quality during specimen testing.

Post-analytical Considerations

  • Accurate reporting of results is essential; communication with healthcare providers should be efficient.

Principles of Medical Laboratory Science Practice

Lecture Instructor: Agabao, Princess Jonalyn, RMT

Pre-analytical Considerations in PhlebotomyModule Objectives:

  • Identify problem areas in site selection and procedures to follow.

  • Explain handling patient complications during blood collection.

  • Manage procedural errors and ensure appropriate specimen quality.

Pre-analytical Phase:Includes all actions before analysis; neglect can compromise specimen quality and patient health.

Key Definitions:

  • Reference Range: Values used for comparison against a patient’s results; previous results may be considered.

  • Basal State: The body's metabolic state after fasting for 12 hours, ideal for reference ranges.

Influencing Factors:

  • Age: Varies blood component values.

  • Altitude: Affects test results at high elevations.

  • Dehydration, Diet, Exercise, Fever, Gender: Each influences blood analyte levels.

  • Positioning, Pregnancy, Smoking, Stress: Can affect specimen composition.

Venipuncture Sites:Avoid sites with burns, scars, or tattoos. Be cautious with damaged veins, edematous areas, and in obese patients. Consult before using the side of a mastectomy.

Complications and Management:Be aware of allergies, excessive bleeding, fainting, nausea, etc. Monitor for hematomas, iatrogenic anemia, arterial puncture, and ensure infection control.

Quality of Blood Specimens:Address causes of hemoconcentration and hemolysis, ensure proper tube fill, and avoid contamination.

Analytical and Post-analytical Considerations:Follow protocols for testing and ensure accurate reporting of results.