PRE-ANALYTICAL CONSIDERATIONS

• Preanalytical


  Before analysis
• Basal state


  Resting metabolic state of the body early morning after approximately 12 hours fasting
• Basal state is influenced by a number of physiologic variables such as age, gender, and conditions of the body that cannot be eliminated
• Normal/reference values


  Obtained from 100 healthy individuals whose blood was collected in basal state, same age, same physique
• Phases of laboratory testing

  • Pre-analytical
  • Analytical
  • Post-analytical
• Pre-analytical phase


  Begins when a test is ordered and ends when testing begins
• Analytical phase


  Testing phase
• Physiological variables that influence laboratory test results

  • Age
  • Altitude
  • Dehydration
  • Diet
  • Diurnal/Circadian Variations
  • Drug Therapy
  • Exercise
  • Fever
  • Gender
  • Intramuscular Injection
  • Jaundice
  • Body Position
  • Pregnancy
  • Smoke
  • Stress
  • Temperature and Humidity
• Hemoconcentration


  Low body hydration → plasma volume decreases → analytes become more concentrated → falsely elevated results
• Tests that require fasting: FBS, Glucose tolerance test, Triglycerides & lipid panel, Gastrin, Insulin, Aldosterone & renin, Electrolytes
• Diurnal/Circadian Variations


  Affected by body changes within 24 hours
• Melatonin levels should be obtained during night
• Chemotherapy drugs can cause a decrease in blood cells, especially WBCs and platelets
• Many drugs are toxic to the liver, causing elevated levels of liver enzymes: AST, ALP, LDH
• Steroids and diuretics increase amylase and lipase
• Moderate to extreme exercise can cause alterations or inaccuracy in the results
• Fever increases hormones insulin and glucagon, and increases cortisol
• RBC, hemoglobin (Hgb), and hematocrit (Hct) normal values are higher for males than for females
• Intramuscular injection increases levels of creatine kinase (CK) and the skeletal muscle fraction of LDH
• Jaundice


  Icteric: deep yellow to yellow-brown color of serum or plasma, interferes with chemistry tests based on color reactions
• Changing body position from supine to upright causes hemoconcentration
• Pregnancy causes lower RBC counts due to dilution effect
• Smoking increases cholesterol, cortisol, glucose, growth hormone, triglycerides, WBC counts, and RBC counts and hemoglobin, but decreases immunoglobulins
• Stress increases WBC counts, decreases serum iron, and increases ACTH, catecholamine, and cortisol
• Temperature and humidity can cause hemoconcentration
• Common pre-analytical errors


  • Incorrect test ordered
  • Inadequate patient preparation
  • Misidentification of patient
  • Wrong container/wrong additive
  • Short draws/ wrong anticoagulant/blood ratio
  • Prolonged tourniquet time
  • Hemolysis due to incorrect technique
  • Inadequate mixing/clots
  • Mislabeling of specimens
  • Improper transport
  • Processing Errors
• Bilirubin is photosensitive and may falsely decrease when exposed to light
• Incomplete centrifugation and incorrect log-in can lead to processing errors
• Problem venipuncture sites


  • Burns, scars, or tattoos
  • Damaged Veins
  • Edema
  • Hematoma
  • Mastectomy
  • Obesity
• Edema


  May yield inaccurate test results (contamination with tissue fluid), veins are harder to locate, tissue is often fragile and easily injured, healing may be prolonged, increased body fluid causes analytes to become diluted
• If both arms have edema, check legs (but ask permission from doctor before extracting)
• Hematoma


  Swelling or mass of blood caused by blood leaking from a blood vessel during or following venipuncture, major reason is failure to apply pressure
• If right breast was removed, you cannot get from right arm for 5-10 years due to lymphostasis
• Obesity makes veins deep and difficult to find, so the median cubital vein or cephalic vein should be used
• Vascular access devices


  • Arterial Line
  • Arteriovenous shunt/AV fistula
  • Heparin or Saline lock
  • Intravenous (IV) Sites
  • Previously active IV sites
  • Blood Sampling Device
  • Central Vascular Access Device (CVAD)
• Performing Venipuncture Below an IV

  1. Ask the nurse to turn off the IV for 2 minutes

  2. Apply the tourniquet distal to the IV

  3. Select a venipuncture site distal to the IV

  4. Perform the venipuncture in a different vein than the one with the IV if possible

  5. Ask the nurse to restart the IV after the specimen has been collected

  6. Document that the specimen was collected below an IV, indicate the type of fluid in the IV, and identify which arm was used
• Patient complications


  • Allergy to equipment and supplies
  • Excessive Bleeding
• Allergy to equipment and supplies

  Includes adhesive allergy, antiseptic allergy, and latex allergy
• Patients on aspirin or anticoagulant therapy are prone to excessive bleeding
• Central Line


  Line inserted into a large vein such as subclavian and advanced into the superior vena cava