Interpreting Clinical Lab Data

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Interpreting Clinical Lab Data

• Robert L. Wilkins, PhD, RRT
• Professor of CPS
• Loma Linda University

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Interpreting Clinical Lab Data

• Objectives
• 1. Identify the characteristics and function of
  each type of leukocyte.
• 2. Identify the significance of comparing the WBC
  count to the neutrophil count in patients with
  pneumonia.
• 3. Identify common causes for increases and
  decreases in the neutrophil count.
• 4. State how the rule of three is useful for
  interpretation of the RBC count and indices.

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Divisions of the Clinical Lab

• Hematology
• Complete blood count
• WBC count
• Platelets
• RBC count
• Chemistry
• Electrolytes
• Potassium
• Sodium
• Total CO2
• Chloride

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Divisions of the Clinical Lab

• Microbiology
• Sputum gram stain
• Sputum culture and sensitivity
• Pleural fluid culture and sensitivity
• Blood Bank
• - blood typing and storage

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CELL MORPHOLOGY
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Cell Morhphology (neutrophil)

• Segmented neutrophil (40-70 of WBCs)
• Life span of about 10 days
• Moves from bone marrow to blood to tissues
• Mature more quickly under stressful conditions
• Primary defense for bacterial infections

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Cell Morhphology (neutrophil)
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The Neutrophil

• Once in the peripheral blood, it can be in the
  circulating pool (CP) or the marginated pool (MP)
  (approx. 50)
• cells in MP not counted in CBC
• Shift from the MP to the CP can occur with
  stress, trauma, catecholamines, etc.
• This results in a transient leukocytosis
• Such leukocytosis can last 4 to 6 hours

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The Neutrophil

• Present in band and segmented forms
• Bands make up lt 5 of circulating neutrophils
  normally
• Left shift is seen as an increase in the number
  of bands and is common with acute infection
• Main function is to locate, ingest, and kill
  bacteria and other foreign invaders

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Cause of Neutrophilia

• Pathologic
• Bacterial infection
• Certain viruses and fungi
• Inflammatory responses to tissue death
• Burns
• Snake bites
• Drugs
• steroids
• lithium

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Causes of Neutrophilia (cont.)

• Physiologic
• Pseudoneutrophilia (shift of cells from the MP to
  CP)
• Catecholamines
• Acute stress
• Other inflammatory responses
• Neoplastic growth
• Metabolic disorders

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Pools of Neutrophils

• Bone marrow many banded forms are present
  neutrophilia with lots of bands suggest bone
  marrow was source
• Circulating Pool used to deal with day to day
  invasion of the body by organisms
• Marginated Pool no bands respond to physiologic
  stimulation

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Causes of Neutropenia

• Decreased Production of WBCs
• bone marrow diseases
• malignancies that affect the bone marrow
• Increased Neutrophil Destruction
• overwhelming infection
• certain bacteria
• immune reactions
• Pseudoneutropenia (shift of cells from CP to MP)
• viral infections
• hypothermia

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Cell morphology (Eosinophil)

• Segmented eosinophil
• Life span 14 days
• Spends little time in the blood before it locates
  in the skin, GI tract, or respiratory tract
• Only 1 of mature cells are located in blood

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The Eosinophil

• Also function as phagocytes but appear to be less
  potent than neutrophil
• Drawn to sites of hypersensitivity reactions by
  mast cell chemotactic factors
• Often found in sputum of asthmatics
• May play a role in pathogenesis of lung dz
• Play a role in parasitic infections

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The Basophils

• Mature basophil
• Least common of WBCs (lt 2)
• Nucleus does not always segment
• Increase in response to same conditions that
  cause eosinophils to respond

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The Monocytes

• Also not common in circulating blood
• Stay in blood for about 70 hours
• Become macrophages in tissue and live for several
  months or longer

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The Monocytes

• Primary role is phagocytosis
• Play large role in ingesting cellular debris
• Become activated when direct contact with
  microorganisms occurs
• Activated cell has greater motility, enzyme
  activity and killing capacity (causes fever)
• Also play a role in immunity

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The Lymphocytes

• May mature into B or T cells
• Main function is antigen recognition and immune
  response
• Life span quite varied (up to two years)
• Can pass back and forth between blood and tissues

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Lymphocytes B T types

• B cells are not only produced in the bone marrow
  but also mature there.
• However, the precursors of T cells leave the bone
  marrow and mature in the thymus (which accounts
  for their designation)

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Types of Lymphocytes

• B lymphocytes (or B cells) are most effective
  against bacteria their toxins plus a few
  viruses
• T lymphocytes (or T cells) recognize destroy
  body cells gone awry, including virus-infected
  cells cancer cells.
• T cells come in two types helper cells and
  suppressor cells normally the helper cells
  predominate.

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Lymphocyte Count Decreased

• Decreased
• AIDS
• Bone Marrow suppression
• Aplastic Anemia
• Steroids
• Neurologic Disorders
• Multiple Sclerosis
• Myasthenia Gravis
• Gullain Barre Syndrome

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Lymphocyte count Increased

• Influenza
• Pertussis
• Tuberculosis
• Mumps
• Cytomegalovirus Infection
• Infectious Mononucleosis
• Infectious Hepatitis
• Viral pneumonia

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Interpreting the CBC

• What is total white cell count?
• If elevated (gt11,000), what type of WBC is the
  culprit?
• Is it the neutrophils, eosinophils, lymphocytes,
  basophils, or monocytes?
• Marked leukocytosis is usually due to neutrophils
  or lymphocytes.

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Interpreting the CBC
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Interpreting the CBC

• If the neutrophils are causing the leukocytosis,
  compare the neutrophil to total WBC.
• The neutrophils indicates the severity of the
  infection the total WBC reflects the quality of
  the immune system

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Interpreting the CBC (Case 1)

• 85 yr old female with pneumonia
• Total WBC is 11,500
• Neutrophil 80 (9200) bands 5
• This indicates that a severe infection is present
  but the immune system is unable to respond
  appropriately.
• Prognosis poor.

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Interpreting the CBC (Case 2)

• 5 yr old male with pneumonia
• WBC 18,000
• Neutrophils 60 (10,800)
• Marked leukocytosis and normal range for
  neutrophils indicates moderate infection but
  excellent immune system response
• Excellent prognosis

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Interpreting the CBC (Case 3)

• 10 yr old male admitted for pneumonia
• WBC 16,000
• neutrophils 75 (12,000) (1800-7500)
• Bands 5 (800) (0-100)
• Eosinophils 1 (160) (0-600)
• Lymphocytes 10 (1600) (900-4500)
• Basophils 0 (0) (0-100)
• Monocytes 3 (480) (90-1000)

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Interpreting the CBC (Case 3)

• Interpretation
• neutrophilia probably due to bacterial pneumonia
• left shift indicative of severe infection
• the source of the neutrophils is the bone marrow
  since many bands are present

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Case Study 4

• 20 yr old male admitted following MVA
• WBC 14,500 75 neutrophils 1 bands
• Leukocytosis due to neutrophilia
• History and low per cent of bands suggest
  pseudoneutrophilia
• Due to liberation of marginated neutrophils in
  the intravascular system

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Interpreting the CBC

• What is indicated by leukopenia?
• 1. Bone marrow failure
• cancer e.g. leukemia, lymphoma
• 2. Overwhelming infection
• severe pneumonia pt who has poor immune system
  and cant produce enough WBCs
• 3. Shift of neutrophils to MNP (viral infections
  and hypothermia)

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Platelet Count

• Normal count is 140,000 to 440,000/mm3
• Life span of about 10 days
• Low platelet counts (thrombocytopenia) cause
  excessive bleeding
• Thrombycytopenia is common with the use of
  heparin, DIC, bone marrow disease, liver failure
  and sepsis

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Platelet
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Platelet (Activated)
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Red Blood Cells
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Red Blood Cells (Erythrocytes)

• Produced in the bone marrow
• Life span of about 120 days
• Primary function is gas transport
• Immature version has nucleus and is called a
  reticulocyte

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Interpreting the RBC count

• Normal values
• Men 4.2 5.4 million/mm3
• Women 3.6 5.0 million/mm3
• Anemia
• abnormal Decrease in RBC count
• - decreased production
• - increased destruction (hemolysis)
• - blood loss

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Interpreting the RBC count

• 3. Increased RBC count Polycythemia
• A. Primary
• B. Secondary
• living at altitude
• chronic lung/heart disease
• tobacco use/carbon monoxide
• C. Relative Polycythemia
• dehydration

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Red Blood Cell Indices

• Mean Corpuscular Volume (MCV)
• Volume occupied by a single RBC
• Increase in MCV is known as Macrocytic anemia.
• Decrease in MCV is known as Microcytic anemia.
• Mean Corpuscular Hemoglobin Concentration
• (MCHC)
• Measure of the concentration of hemoglobin in an
  average RBC
• Decrease in MCHC is known as Hypochromic anemia
• Normal is known as Normochromic anemia.

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Red Blood Cell Indices

• Normocytic anemias
• Blood loss
• Hemolytic anemia
• Microcytic anemias (lt80 fL)
• Iron deficiency
• Macrocytic anemias (gt100 fL)
• Folic acid deficiency
• Vitamin B12 deficiency
• Some COPD patients
• femtoliters

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Red Blood Cell Indices
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Hematocrit
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The RULE of Three

• Applies to normocytic, normochromic erythrocytes
  only
• Useful to detect laboratory error in measuring
  the Hb, HCT, and RBC count
• 3 times the RBC count should Hb
• 3 times Hb should Hct

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The RULE of Three

• RBC 3.0 x 1012 3 x 3 9
• Hb 9.2 g/dL 3 x 9.2 27.6
• Hct 28

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Interpreting the Red Blood Cells

• CBC Results Normals
• RBC (x1012/L) 4.2 4.2-5.4
• Hgb (g/dL) 10.6 ? 11.5-15.5
• Hct 34.9 ? 38-47
• MCV (?m3) 77.0 ? 80-96
• MCHC 30.4 ? 32-36
• Interpretation Microcytic, hypochromic anemia
  rule of 3 does not apply

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Reticulocyte Count

• Normal values
• 0.5 1.5 of RBC
• Helpful to identify cause of Anemia
• Increase indicates Anemia is due to Blood loss
• Decrease indicates Anemia is due to Bone marrow
  disease

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Bibliography

• Steine-Martin Clinical Hematology, 2nd edition,
  Lippincott, Philadelphia, 1998.
• Kaplan Clinical Chemistry, 4th edition, Mosby,
  St. Louis, 2003.
• Wilkins Clinical Assessment in Respiratory Care,
  5th edition, Mosby, St. Louis, 2005.