phleb midterms

• The preanalytical phase of the testing process starts when a test is ordered and ends when testing begins.
• If not properly addressed, numerous factors and variables associated with this phase of the testing process can lead to errors that can:

  • compromise specimen quality
  • harm the health and safety of the patient
  • increase the cost of medical care
• Reference Ranges/Intervals

  • Result values for most tests are established using specimens from normal, healthy individuals.
  • commonly called a reference range or reference interval.
  • often called normal values
• Basal state refers to the resting metabolic state of the body early in the morning after fasting for approximately 12 hours.
• • A basal-state specimen is ideal for inpatients because the effects of diet, exercise, and other controllable factors on test results are minimized or eliminated.
  • Basal state is influenced by physiologic patient variables such as age, gender, and conditions of the body that cannot be eliminated.
• Age

  • RBC and WBC values are normally higher in newborns than in adults.
  • Some physiologic functions such as kidney function decrease with age.
  • Hormone levels may also vary by age (estrogen and growth hormone [GH] decrease with advanced age).
• Altitude

  • RBCs carry oxygen. Decreased oxygen levels at higher altitudes cause the body to produce more RBCs to meet the body’s oxygen requirements; the higher the altitude, the greater the increase.
  • Thus, RBC counts and related determinations such as hemoglobin (Hgb) and hematocrit (Hct) have higher reference ranges at higher elevations.
  • Other analytes that increase at higher elevations include C-reactive protein and uric acid.
  • Analytes that decrease in value at increased altitude include urinary creatinine (which in turn affects creatinine clearance tests) and plasma renin.
• Dehydration which can occur, for example, with persistent vomiting or diarrhea, causes hemoconcentration

  Blood components affected include:

  • RBC

  • Enzymes

  • Iron (Fe)

  • calcium (Ca)

  • Sodium (Na + )

  • Potassium (K + )

  • Coagulation factors..
• Diet

  • Blood composition can be altered by the ingestion of food and drink.

  • Blood specimens collected soon after a meal or snack are unsuitable for many laboratory tests.

  • Diet effects on analytes are generally temporary and vary depending upon the amount and type of food or drink and the length of time between ingestion and specimen collection.

  • Requiring a patient to fast eliminates most dietary influences on testing.

  • The typical fast is 8 to 12 hours depending on the test.
• Fasting beyond 12 hours can cause serious health problems, such as:

  electrolyte imbalance and heart rhythm disturbances
• analytes that can be significantly affected:

  • ↑ Ammonia, urea, and uric acid- high-protein diets
  • ↑Cortisol and adrenocorticotropic hormone (ACTH)- caffeine
  • ↑ Glucose (blood sugar)- carbohydrates or sugar-laden substances
  • ↑ insulin levels- carbohydrates
  • ↑ Lipid- butter or margarine, cheese, cream, oils, and some enteral (tube feeding) preparations.
  • ↑ Triglycerides, liver enzymes, liver function analytes- chronic consumption or alcohol ingestion
  • ↓Hgb and electrolyte balance can be altered- excessive amounts of water and other fluids.
• Diurnal/Circadian Variations

  • Factors that play a role in diurnal variations include posture, activity, eating, daylight and darkness, and being awake or asleep.
  • For example, melatonin levels are affected by light; they increase at night when it is dark and decrease during daylight hours.
• blood components high in morning:

  • aldosterone, bilirubin, cortisol, hemoglobin, insulin, iron, potassium, testosterone, and RBCs.
• blood components low in morning:

  • eosinophils, creatinine, glucose, GH, triglycerides, and phosphate
• Cortisol, TSH, and iron can differ by 50% or more between morning and late afternoon.
• • Chemotherapy drugs can cause a decrease in blood cells, especially WBCs and platelets.
  • Drugs that are toxic to the liver results to increased levels of liver enzymes such as:

  1. aspartate aminotransaminase (AST)
  2. alkaline phosphatase (ALP)
  3. lactate dehydrogenase (LDH),

  And decreased production of clotting factors.
• Erythromycin and acetaminophen (e.g., Tylenol) can increase AST and bilirubin levels and give a false indication of abnormal liver function.
• Opiates such as morphine increase levels of liver and pancreatic enzymes.
• Oral contraceptives can affect the results of many tests. For example, they can elevate the erythrocyte

  sedimentation rate (ESR) and decrease levels of vitamin B12 .
• Steroids and diuretics can cause pancreatitis and an increase in amylase and lipase values.
• Thiazide diuretics (blood pressure medications) can elevate calcium and glucose levels and decrease sodium and potassium levels
• According to CAP guidelines, drugs that interfere with blood tests should be stopped 4 to 24 hours prior to obtaining the blood sample for testing. Drugs that interfere with urine tests should be avoided for 48 to 72 hours prior to the urine sample collection.
• Exercise

  The following are examples of the effects of exercise on blood components:

  • Arterial pH and PaCO2 levels are reduced by exercise.
  • Glucose, creatinine, insulin, lactic acid, and total protein can be elevated by moderate muscular activity.
  • Potassium (K + ) is released from the cells during exercise, increasing levels in the plasma. Levels generally return to normal after several minutes of rest.
• Do not allow the patient to pump his or her fist during a blood draw. The simple exercise of pumping the fist during venipuncture is enough to erroneously increase potassium levels.
• Vigorous physical exercise shortly before blood collection can temporarily increase total cholesterol levels by 6% or more.

  Remain elevated for up to an hour after the exercise has stopped.
• Hemostasis is your body’s natural reaction to an injury that stops bleeding and repairs the damage.
• Fever

  • Fever-induced hypoglycemia increases insulin levels, followed by a rise in glucagon levels.
  • Fever also increases cortisol and may disrupt its normal diurnal variation.
• Sex

  • RBC, Hgb, and Hct normal values are higher for males than for females.
• Intramuscular Injection

  • Increase levels of CK and the skeletal muscle fraction of LDH.
  • It is recommended that CK and LDH levels be drawn before intramuscular injection or at least one hour after injection.
  • Muscular trauma from injuries or surgery can also increase CK levels.
• • Jaundice (from the French word jaune, which means yellow), also called icterus, is a condition characterized by increased bilirubin in the blood.
  • High bilirubin levels result in deposits of the yellow pigment in the skin, mucous membranes, and sclerae (whites of the eyes), giving the patient a yellow appearance.
• Position

  • Body position before and during blood collection can influence specimen composition.
  • Going 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%.
• Only protein-free fluids can pass through the capillaries
• • The blood concentration of components that are protein in nature such as: aldosterone, bilirubin, blood cells, calcium, cholesterol, iron, protein, and renin—increases.
  • In most cases, the concentration of freely diffusible blood components is not affected by postural changes.
• 30 minutes of standing; increase in potassium

  15 minutes of standing; increase in RBC
• A change in position from lying to standing can cause up to a:

  • 15% increase in total cholesterol and high-density lipoprotein (HDL) cholesterol results
  • 10% to 12% higher triglyceride results
• Patients are typically required to be recumbent (lying down) for at least 30 minutes prior to aldosterone specimen collection, and plasma renin activity levels require documentation of the patient’s position during collection.
• postural pseudoanemia (posture-related false anemia), a substantial decrease in hematocrit values due to an increase in plasma that could be mistaken for blood loss or acute anemia
• Pregnancy

  • There is an increase in body fluid that are normal during pregnancy which causes a diluting effect on RBCs, leading to lower RBC counts
• Smoking

  • Patients who smoke prior to specimen collection may have increased cholesterol, cortisol, glucose, GH, and triglyceride levels as well as WBC counts.
  • Glucose levels in patients with diabetes are especially affected by smoking; in fact, studies have shown that nicotine is the primary cause of elevated glucose levels in smokers who are diabetic.
• Smoking can also affect the body’s immune response, typically lowering the concentrations of immunoglobulins IgA, IgG, and IgM, and increasing levels of IgE.