PMLS 2 LEC MODULE 5

• The preanalytical (before analysis) or pre-examination phase of the testing process begins in the laboratory when a test is ordered and ends when testing begins
• Numerous factors associated with this phase of the testing process, if not properly addressed, can lead to errors that can compromise specimen quality, jeopardize the health and safety of the patient, and ultimately increase the cost of medical care
• A phlebotomist must have, in addition to the technical skills needed to perform a blood draw, the ability to recognize preanalytical factors and address them to avoid or reduce any negative impact
• This part of the module will address

  • Physiological variables
  • Problem venipuncture sites
  • Various types of vascular access devices
  • Patient complications and conditions
  • Procedural errors
  • Specimen quality issues
• Reference range


  Values which patient results are compared to
• Basal state


  The resting metabolic state of the body early in the morning after fasting for approximately 12 hours
• A basal state specimen is ideal for establishing reference ranges on inpatients because the effects of diet, exercise, and other controllable factors on test results are minimized or eliminated
• Basal state is influenced by

  • Age
  • Gender
  • Conditions of the body that cannot be eliminated
• Age


  • Values for blood components vary considerably depending upon the age of the patient
  • RBC and WBC values are normally higher among newborns than in adults
  • Kidney functions decrease with age
• Altitude


  • Test results for some blood analytes show significant variation at higher elevations compared with results at sea level
  • Analytes generally take weeks to adapt to high elevations/altitude but adapt to return to sea level within days
• Analytes affected by high altitude

  • Increased levels: RBC count, Hemoglobin, Hematocrit, Uric acid
  • Decreased levels: Urinary creatinine, Plasma renin
• Dehydration


  • Dehydration is the decrease in body fluid
  • Dehydration may happen with persistent vomiting or diarrhea, which causes hemoconcentration
  • Dehydrated patients may not accurately reflect the patient's normal status
  • It is often difficult to obtain blood specimens from dehydrated patients
• Analytes that increase during dehydration

  • RBC
  • Enzyme
  • Iron
  • Calcium
  • Sodium
  • Coagulation factors (clotting factors)
• Fasting


  • Strictly no ingestion of food approximately 8-12 hours overnight, though drinking of water is allowed for some fasting patients
  • Overfasting beyond 12 hours can cause serious health problems
• Examples of how some analytes can be significantly affected by the consumption of certain types of food or drink

  • Ammonia, urea, and uric acid levels may be elevated in patients on high-protein diets
  • Cortisol and ACTH levels increase with the consumption of beverages containing caffeine
  • Glucose levels increase dramatically with the ingestion of carbohydrates or sugar-laden substances
  • Hemoglobin levels can decrease and electrolyte balance can be altered by drinking excessive amounts of water and other fluids
  • Lipid levels increase with ingestion of foods such as butter or margarine, cheese, cream, and some enteral preparations
  • Triglycerides, certain liver enzymes, and other liver function analytes are increased by chronic consumption or recent ingestion of large amounts of alcohol
• Effects of long-term starvation

  • Increased levels: Creatinine, Ketone, Uric acid, Cholesterol, Triglycerides, Urea
  • Decreased levels: None listed
• Diurnal/Circadian variations


  • The levels of many blood components normally exhibit diurnal (happening daily) or circadian (having a 24-hr cycle) variations or fluctuations
  • Factors that play a role: Posture, Activity, Eating, Being awake or asleep, Daylight and darkness
• Examples of analytes with diurnal/circadian variations

  • Melatonin, Cortisol, Renin, Thyroid-stimulating hormone, Aldosterone, Bilirubin, Hemoglobin, Insulin, Iron, Potassium, Testosterone, RBC, Eosinophils, Creatinine, Glucose, Growth hormone, Triglycerides, Phosphates
• Drug therapy


  • Some drugs alter physiological functions, causing changes in the concentration of certain blood analytes
  • Drugs can also interfere with the actual test procedure, causing false increases or decreases in test results
• Examples of drugs that can alter physiologic function and the analytes they affect

  • Increased: Chemotherapy drugs (WBC, platelets), Oral contraceptives (ESR, Vitamin B12), Steroids and diuretics (Amylase, lipase)
  • Decreased: Most drugs (AST, ALP, LDH, Clotting factors), Thiazide diuretics (Calcium, glucose, Sodium & potassium)
• Drugs that interfere with blood tests should be stopped or avoided 4 to 24 hours prior to obtaining blood samples for testing, and drugs that interfere with urine tests should be avoided for 48 to 72 hours prior to the urine sample collection
• Examples of the effects of exercise on blood components

  • Increased: Glucose, Creatinine, Insulin, Lactic acid, Total protein, Potassium, Creatine kinase (CK), Lactate dehydrogenase (LDH), Cholesterol
  • Decreased: Arterial pH, Carbon dioxide, Platelets
• Fever


  • Fever affects the levels of a number of hormones
  • Fever-induced hypoglycemia increases insulin levels, followed by a rise in glucagon levels
  • Fever also increases cortisol and may disrupt its normal diurnal variation
• Gender


  • A patient's gender affects the concentration of a number of blood components
  • RBC, hemoglobin and hematocrit values are higher among males than in females
• Intramuscular injection


  • A recent intramuscular injection can increase levels of creatine kinase (CK) and the skeletal muscle fraction of LDH
  • Consequently, it is recommended that CK and LDH levels be drawn before intramuscular injection or at least 1 hour after injection
• Jaundice (icterus)


  • A condition characterized by increased bilirubin in the blood, leading to deposits of yellow bile pigment in the skin, mucous membrane and sclera, giving the patient a yellow appearance
  • The color can interfere with blood chemistry tests based on color reactions and may also interfere in reagent-strip analyses on urine
• Position


  • Body position before and during blood collection can influence specimen composition
  • From supine (lying down on the back) to an upright sitting or standing position causes blood fluids to filter into the tissues, decreasing plasma volume in an adult up to 10%
  • This increases the concentration of components that are protein in nature or bound to protein
• Examples of protein-bound components and components that are protein in nature that may increase

  • Aldosterone
  • Calcium
• Jaundice


  Abnormal deep yellow to yellow-brown color of serum, plasma, or urine specimens due to high bilirubin levels
• Position


  Body position before and during blood collection can influence specimen composition
• Postural changes


  1. From supine (lying down on the back) to an upright sitting or standing position

  2. Causes blood fluids to filter into the tissues, decreasing plasma volume in an adult up to 10%

  3. Only protein-free fluids can pass through the capillaries, consequently the blood concentration of components that are protein in nature or bound to protein increases
• Components that may increase due to postural changes

  • Aldosterone
  • Calcium
  • Iron
  • Cholesterol and HDL (15% variation)
• Standing position


  1. RBC count may increase approximately 15 minutes

  2. Potassium ion levels significantly increase within 30 minutes due to release of intracellular potassium from muscle
• Lipid profiles should be collected in a consistent manner after the patient has been either lying down or sitting quietly for a minimum of 5 minutes
• Calling outpatients into the drawing area and having them sit in the drawing chair while paperwork related to the draw is readied can help minimize effects of postural changes on some analytes
• Pregnancy


  Causes physiologic changes in many body systems
• Smoking


  May affect a number of blood components, the extent depends on the number of cigarettes smoked
• Effects of smoking before specimen collection

  • Increase in cholesterol, growth hormone, cortisol, triglycerides, glucose, WBC count
• Effects of chronic smoking

  • Increase in RBC count and hemoglobin levels
• General effects of smoking

  • Decrease in immunoglobulins IgA, IgG, IgM
  • Increase in immunoglobulin IgE