Blood Analysis and Testing Notes

Plasma

  • Plasma is the liquid portion of the blood.
  • Red blood cells clump and coagulate when blood settles, indicating the cessation of circulation.
  • Red blood cells are "cars," and plasma is the "freeway" of the body.
  • Plasma transports formed elements and other substances throughout the body.
  • Plasma composition:
    • Approximately 90% water
    • 9% protein
    • 1% other chemical substances
  • Plasma includes:
    • Albumin
    • Prothrombin (PT or clotting factor)
    • Fibrinogen
    • Immunoglobulins (for vaccine titers and immunity)

Erythrocyte Sedimentation Rate (ESR)

  • ESR measures the rate at which erythrocytes separate from plasma and settle in a calibrated tube in one hour.
  • It is a general indicator of inflammation.
  • Commonly used in rheumatology, oncology (cancer), and hematology (study of blood).
  • Westergren method is the recommended method.
  • Procedure:
    • Fill the tube completely with blood (purple or capillary tube).
    • Keep the tube vertical and undisturbed for one hour.
    • Tilting can cause false results.
  • Increased ESR is seen in:
    • Acute and chronic infections
    • Rheumatoid arthritis
    • Lupus
    • Autoimmune conditions
    • Some cancers
  • See page 864 in the book for the ESR collection method.

Coagulation Testing

  • Tests clotting factors, especially for patients on blood thinners (Coumadin, heparin, Plavix).
  • Similar to glucose testing: finger prick, blood on testing strip.
  • Can be done instead of sending out for a blue top tube (PT, PTT, INR).
  • PT (prothrombin time) results are reported in seconds for blood to clot when mixed with thromboplastin reagent.
  • INR (international normalized ratio) was created by the World Health Organization because PT test results can vary depending on the thromboplastin reagent used.
  • Results will vary with brand of test used, but will still be accurate.

Complete Blood Cell Count (CBC)

  • Most frequently ordered laboratory procedure for blood specimens.
  • Provides information about blood components.
  • Whole blood consists of formed elements suspended in plasma.
  • Plasma makes up about 55% of blood volume.
  • Formed cellular elements make up the remaining 45%.
  • CBC includes:
    • Red blood cell count
    • Hematocrit
    • Hemoglobin
    • Red blood cell indices
    • White blood cell count and differential
    • Platelet estimation
  • CBC can indicate anemia or infection.

Red Blood Cells (RBCs)

  • Function: transport oxygen to tissues.
  • Red blood cell count is part of a CBC.
  • Approximates the number of circulating red blood cells.
  • Normal values:
    • 4,000,000 to 6,000,000 cells/mm\text{m}^3
  • Usually higher in men than women due to higher blood volume.
  • Reference ranges (page 867):
    • Newborns (Hemoglobin): 10-20 \text{ g/dL}
    • Children: 8.9-12 \text{ g/dL}
    • Children 2-17: 10.2-16.9 \text{ g/dL}
    • Adult Females: 11.6-15 \text{ g/dL}
    • Adult Males: 13.2-16 \text{ g/dL}

Hematocrit

  • Measures the percent of packed red blood cells in a volume of blood.
  • Drops of blood collected by capillary puncture and centrifuged.
  • Packed red blood cells are at the bottom of the tube.
  • Microhematocrit is determined by comparing the concentration of red blood cells with the total volume of the full blood cell sample.
  • Can also be calculated using RBC count and RBC size value for automated cell counter.
  • Normal values:
    • Women: Low 36\%
    • Men: High 52\%

Hemoglobin

  • Roughly measures the oxygen-carrying capacity of blood.
  • Dark red blood has more hemoglobin than pale red blood.
  • Handheld devices are available to measure hemoglobin.
  • Normal hemoglobin values vary throughout life.
  • Indicator of anemia.

H and H

  • Refers to hemoglobin and hematocrit.
  • Quick Mental Calculation: \text{Hemoglobin value} \times 3 \pm 3 \approx \text{Hematocrit value}

Red Blood Cell Indices

  • Provide information about red blood cell disorders.
  • MCV (mean cell volume): total volume of red blood cells.
  • MCH (mean cell hemoglobin): total hemoglobin in the sample of blood.
  • MCHC (mean cell hemoglobin concentration): ratio of hemoglobin to hematocrit.
  • Used to classify anemias and select additional tests to determine the cause.

White Blood Cell Count (WBC)

  • Normal WBC counts vary with age.
  • Higher in newborns, decreases throughout life.
  • Average adult range: 4,500 to 11,000 cells/mm\text{m}^3
  • Gives an approximation of the total number of leukocytes in circulating blood.
  • Helps determine if an infection is present and aids in the diagnosis of leukemia.
  • Increase in normal WBC: leukocytosis.
  • Leukemia: cancer of the blood.

Differential Cell Count

  • Analyzes and quantitates the types of white blood cells in a blood sample.
  • Performed manually using stained blood smears and a microscope or with automated instruments.
  • Different types of cells:
    • Red blood cell
    • Platelet
    • Neutrophil
    • Bands (horse-shaped nuclei)
    • Eosinophils
    • Basophils
    • Monocytes
    • Lymphocytes
  • Automated cell counters gather information about cell size, internal structure, and density.

Platelet Analysis

  • Normal platelet count: 150,000 to 450,000/mm\text{m}^3
  • Morphology observed for abnormalities.
  • Increase in platelets: thrombocytosis.
  • Decrease in platelets: thrombocytopenia.
  • Excessive clumping is reported.

Preparing a Blood Smear

  • Enables the examiner to view cellular components of blood in as natural of a state as possible.
  • Spread a drop of blood on a clean glass slide.
  • Types: cover glass smear, spun smear, or wedge smear.
  • Allow to dry propped up.
  • Write the patient's name on the frosted end of the slide.
  • Fix the slide in methanol.
  • Cover glass smear: placing a single drop between cover slips and quickly pulling them apart.
  • Spun smear: uses a centrifuge to distribute blood on a slide.
  • Wedge smear: placing a drop of blood one-half inch from the right end of the glass slide.

Staining Blood Smears

  • Wright's stain is commonly used.
  • Polychromatic stains contain dyes that stain various cell parts.
  • Stains usually contain a blue stain and eosin (a red-orange stain).
  • Most commonly used differential stain is the Wright stain.

Identification of Normal Blood Cells

  • Slide is examined near the feathered end of the smear where cells are barely touching and are easiest to identify.
  • Observation of cells can provide more information than cell counts alone.
  • Examined with the oil immersion objective of a microscope.

Differential Examinations

  • Specific areas are stained and smear examined microscopically.
  • Must be where red blood cells are touching but not clumped together.
  • Focus on one area and count and classify 100 consecutive white blood cells while moving in a specific winding pattern through the smear.
  • For manually prepared smears, the appropriate area would be the feathered edge.
  • Many disease states alter the ratio of the different types of leukocytes.

Red Blood Cell Morphology

  • Normally stained red blood cells are the same size and shape and are filled with hemoglobin.
  • Any variations from the normal state are reported.
  • Looking for:
    • Size
    • Shape
    • Content when evaluating.

Immunohematology

  • Study of blood and the immune system.
  • Formerly called the blood bank.
  • Responsible for blood typing.
  • Compatibility testing to prevent transfusion reactions.
  • Identify potential Rh incompatibility problems in expectant mothers.
  • RhoGAM shot is administered to Rh-negative mothers to prevent the body from attacking an Rh-positive fetus.
  • RH incompatibility between an expectant mother and the unborn child may result in hemolytic disease of the newborn.

Blood Typing

  • Certain blood types are more common in certain countries.
  • Racial and ethnic differences in blood types and composition exist due to inheritance.
  • More than 600 antigens and more than 20 other blood antigen systems are known.
  • Two major blood antigen systems are the ABO system and the Rh system.

Determination of ABO Blood Group

  • Blood typing is a simple test but not CLIA waived, so it is done in a lab.
  • The test detects the presence of A or B antigens on red blood cells.
  • Blood transfusions should ideally be specific (e.g., A positive to A positive).
  • O negative is the universal donor because there are no circulating antibodies.

Determination of the Rh Factor

  • Also a simple test but not CLIA waived, so must be done in a lab.
  • Test detects the presence of proteins on the surface of red blood cells.
  • If you are Rh positive, you won't have a problem.
  • If hemolytic disease of the newborn develops and you're Rh negative, the mother may develop antibodies to the D antigen.
  • Mother's immune system may begin to produce more antibodies if she was sensitized during the first pregnancy.

Legal and Ethical Issues Related to Transfusions

  • The Blood Safety Act of 1991 ensures that all blood donors are tested for HIV and other viable diseases like hepatitis.
  • Providers must explain to each elective surgery patient the chances of needing a blood transfusion.
  • Take religious or cultural beliefs into consideration (e.g., Jehovah's Witnesses, Muslims).
  • Autologous transfusions: using your own blood.

Blood Glucose Testing

  • Patient's blood glucose levels can be screened with a glucometer.
  • Routinely monitored by patients with diabetes (type 1 or type 2) and gestational diabetes.
  • Blood glucose tolerance test (GTT) can check for diabetes mellitus (page 875).
  • If the blood glucose level exceeds 200 \frac{\text{g}}{\text{dL}}, glucose escapes into the urine because the renal tubules are no longer able to absorb the excess amount..Hopefully in processing your own sugar and processing itself, your body will filter out that extra sugar through your urine a alleviate the blood.
  • Self-monitoring of blood glucose is an important part of treatment of diabetes.

Hemoglobin A1C Testing

  • It gives information about the average blood glucose level during the past two or three months every three months, and it provides the data on the patient's average blood glucose level.
  • Patients can also perform hemoglobin A1C testing at home.
  • This gives information about the average blood glucose level during the past two or three months.
  • Tests are done every three months.
  • Several CLIA waived devices can be used.

Cholesterol Testing

  • Done via blood draw and is part of the CMP (complete metabolic panel).
  • Monitors can measure HDL, total cholesterol, and triglycerides such that, the total fat that can be found in your red blood cells.
  • Adults older than 20 years of age should have a cholesterol test at least every five years.
  • Low-density lipoprotein (LDL) cholesterol reflects an increased risk of heart disease such that you want less than a hundred and over 190 is very, very high.
  • High-density lipoprotein (HDL) protects against heart attacks.That is known as your good cholesterol.

Thyroid Hormone Testing

  • The thyroid is the butterfly gland in the throat.
  • Works within the pituitary gland in your endocrine system, regulating hormones.
  • Produces hormones essential for metabolism, growth, and development.
  • Influenced by the pituitary and hypothalamus glands.
  • CLIA waived test measures thyroid stimulating hormones.
  • The test that you would order to check is a TSH. If you are trying to order a test to check someone's thyroid.
  • Using whole blood from a finger stick, these tests screen patients for hypothyroidism by detecting elevated levels of TSH.

Chemistry Panels

  • Automated blood chemistry panels perform blood chemistry testing to different methodologies may generate different reference ranges and may use different units of measurement such that tests such as a renal or liver panel can determine the level of several related analytes.
  • In general,