PRE ANALYTICAL PMLS

• Diurnal variation


  Fluctuations in biological processes over the course of a day
• Tests affected by diurnal variation


  • Cortisol
  • Adrenocorticotropic hormone
  • Plasma renin activity
  • Aldosterone
  • Insulin
  • Growth Hormone & Acid Phosphatase
  • Thyroxine
  • Prolactin
  • Iron
  • Calcium
• Cortisol


  Peaks 4–6 AM; lowest 8 PM–12 AM; 50% lower at 8 PM than at 8 AM; increased with stress
• Adrenocorticotropic hormone


  Lower at night; increased with stress
• Plasma renin activity


  Lower at night; higher when standing than supine
• Aldosterone


  Lower at night
• Insulin


  Lower at night
• Growth Hormone & Acid Phosphatase


  Higher in afternoon and evening
• Thyroxine


  Increases with exercise
• Prolactin


  Higher with stress; higher levels at 4 and 8 AM and at 8 and 10 PM
• Iron


  Peaks early to late morning; decreases up to 30% during the day
• Calcium


  4% decrease supine
• Effects of exercise


  • Increase: Creatine kinase (CK), aspartate aminotransferase (AST), and lactate dehydrogenase (LD)
  • Potassium: mild to moderate exercise – increase by 0.3 – 1.2 mmol/L, exhaustive exercise – increase by 2-3 mmol/L
  • Prolactin (in long-distance athletes) - Decreased
  • serum gonadotropins and sex steroid (in long-distance athletes) - Decreased
• Effects of diet


  • 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 (blood sugar) levels increase dramatically with the ingestion of carbohydrates or sugar-laden substances
  • Hgb levels Decrease by drinking excessive amounts of water and other fluids
  • Electrolytes Imbalance may occur due to 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 (tube feeding) preparations
  • Stool Occult Blood test Detects gastrointestinal bleeding; may be false positive due to ingestion of meat, fish, iron, and horseradish
  • TAG/TGY, liver enzymes, liver function tests are increased due to chronic consumption of alcohol
• Effects of stress


  • Emotional stress can cause transient (short-lived) elevations in WBCs
  • Mental and physical stresses induce the production of adrenocorticotropic hormone (ACTH), cortisol, and catecholamines
• Posture


  An upright position increases hydrostatic pressure, causing a reduction of plasma volume and increased concentration of proteins. Albumin and calcium levels may become elevated as one changes position from supine to upright. A change in position from lying to standing can cause up to a 15% variation in total and high-density lipoprotein (HDL) cholesterol results.
• Tourniquet application


  May also increase serum enzymes, proteins, and protein-bound substances, including cholesterol, calcium, and triglycerides. Prolonged application results in venous stasis (hemoconcentration).
• Effects of age


  • Newborn – much of the Hb is Hb F
  • Bilirubin concentration rises after birth and peaks at about 5 days
  • Infants have lower glucose level than adults
  • With skeletal growth and muscle development, serum alkaline phosphatase and creatinine levels also increase
  • The elderly secrete less triiodothyronine, parathyroid hormone, aldosterone, and cortisol
  • After age 50, men experience a decrease in secretion rate and concentration of testosterone and women have an increase in pituitary gonadotropins
• Effects of gender


  • After puberty, men have higher alkaline phosphatase, aminotransferase (alanine and aspartate), creatine kinase, and aldolase levels
  • Women have lower levels of magnesium, calcium, albumin, Hb, serum iron, and ferritin
• In vivo interferences from tobacco smoking


  • Smokers have high blood carboxyhemoglobin levels
  • Chronic effects of smoking: Increased Hb, RBC Count, Mean Cell Volume (MCV), and WBC Count, Increased levels of insulin, epinephrine, and growth hormones, Decreased sperm counts and motility and increased abnormal morphology
• In vitro interferences from hemolysis

  • Serum/plasma layer is pink or red
  • Falsely increased in: Potassium, magnesium, iron, lactate dehydrogenase, phosphorus, ammonium, and total protein
  • Normally platelets release potassium during clotting
  • Serum has a slightly higher value of potassium than plasma
• Other interferences


  • Alcohol ingestion: Increases plasma concentration of uric acid, triglycerides, and gamma glutamyltransferase (GGT), Causes hypoglycemia
  • Dehydration: Blood components affected include RBCs, enzymes, iron, calcium, sodium, and coagulation factors
  • Drug therapy: Chemotherapy drugs - decrease in blood cells, especially WBCs and platelets, Many drugs are toxic to the liver - increased levels of liver enzymes such as ALT, AST, LD; decreased production of clotting factors
• Problem areas to avoid in site selection

  • Burns, Scars, and Tattoos
  • Damaged veins (sclerosed/hardened or thrombosed/clotted veins)
  • Edema
  • Hematoma
  • Mastectomy
• Arterial line (A-line or Art-line)


  A catheter that is placed in an artery (radial artery), used to provide accurate and continuous measurement of a patient's blood pressure, used to collect blood gas and other blood specimens, for the administration of drugs, never apply tourniquet or perform venipuncture on an arm with A-line
• Arteriovenous shunt, fistula, or graft


  A permanent surgical connection of an artery and vein by direct fusion (fistula) to be used for dialysis, has a distinctive buzzing sensation called a "thrill" when palpated, never apply tourniquet or perform venipuncture on an arm with a shunt
• Blood sampling device


  A needleless closed blood sampling device is sometimes connected to an arterial or central venous catheter, collecting blood specimens, reduce the chance of infection, prevent needlesticks, and minimize waste associated with line draws, example is the VAMP® (Venous Arterial blood Management Protection system) from Edwards Lifesciences
• Heparin or saline lock


  A catheter or cannula connected to a stopcock or a cap with a diaphragm (thin rubber-like cover), provides access for administering medication or drawing blood, only specially trained personnel, drawing coagulation specimens from this site is not recommended
• Intravenous sites


  An IV line is a catheter inserted in a vein to administer fluid, blood should not be drawn from an arm with IV, previously active IV sites - blood specimens should not be collected from a known previous IV site within 24 to 48 hours of the time the IV was discontinued, follow facility protocol
• Central vascular access devices (CVADs)


  Also called an indwelling line, consists of tubing inserted into a main vein or artery, are used primarily for administering fluids and medications, monitoring pressures, and drawing blood, only specially trained personnel should access CVADs
• Types of central vascular access devices (CVADs)

  • Central Venous Catheter (CVC) or Central Venous Line
  • Implanted Port
  • Peripherally Inserted Central Catheter (PICC)
• Central Venous Catheter (CVC) or Central Venous Line


  A line inserted into a large vein such as the subclavian and advanced into the superior vena cava, proximal to the right atrium, the exit end is surgically tunneled under the skin to a site several inches away in the chest
• Implanted Port


  A small chamber attached to an indwelling line that is surgically implanted under the skin and most commonly located in the upper chest or arm
• Peripherally Inserted Central Catheter (PICC)

  A line inserted into the peripheral venous system (veins of the extremities) and threaded into the central venous system (main veins leading to the heart), is typically placed in an antecubital vein just above or below the antecubital fossa
• Complications associated with blood collection


  • Allergies to equipment and supplies
  • Excessive bleeding (aspirin/anticoagulant therapy)
  • Fainting or syncope - Vasovagal syncope: fainting due to abrupt pain, stress, or trauma
  • Nausea and vomiting
  • Pain
  • Petechiae
  • Seizures/convulsion
• Procedural error risks


  • Hematoma formation - Most common complication of venipuncture, Apply cold compress or ice pack to reduce swelling
  • Iatrogenic anemia - removing blood on a regular basis or in large quantities can lead to iatrogenic anemia in some patients, especially infants, life is threatened if more than 10% of the patient's blood volume is removed at one time or over a short period of time
  • Inadvertent arterial puncture - most often associated with deep or blind probing, rapidly forming hematoma and blood tube fills very quickly, if arterial puncture is suspected, terminate venipuncture immediately and apply pressure to the site for at least 5 minutes
  • Infection - The risk can be minimized by using proper aseptic technique
  • Nerve injury - Causes: Poor site or improper vein selection, inserting the needle too deeply or quickly, movement by the patient as the needle is inserted, excessive or lateral redirection of the needle, or blind probing while attempting venipuncture
  • Reflux of additive - Prevent reflux: the patient's arm must be kept in a downward position, Avoid back-and-forth movement of blood in the tube
  • Vein damage - Numerous punctures in the same area, blind probing, and improper technique
• Specimen quality concerns


  • Hemoconcentration (venous stasis)
  • Hemolysis - Serum or plasma layer is pink (slight hemolysis), dark pink to light red (moderate hemolysis), to dark red (gross hemolysis)
  • Partially filled tubes (short draw) - Short-draw serum tubes such as red tops and SSTs are generally acceptable for testing as long as the specimen is not hemolyzed and there is sufficient specimen to perform the test, Underfilled anticoagulant tubes and most other additive tubes are NOT acceptable for testing
  • Specimen contamination
  • Wrong or expired collection tube
• Troubleshooting failed venipuncture


  • Tube position
  • Needle position - Correct needle position, Needle not inserted far enough, Needle bevel partially out of the skin, Needle bevel partially into the vein, Needle bevel partially through the vein, Needle bevel completely through the vein, Needle bevel against the upper vein wall, Needle bevel against the lower vein wall, Needle beside the vein, Collapsed vein
  • Tube vacuum