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Tufts OpenCourseware
Author: Kanchan Ganda, M.D.

1. CBC: Complete Blood Count

1.1. Summary of CBC Values

  • WBC: 4,000 - 10,000 / mm3
  • RBC: 4.2 - 5.9 million / mm3
  • Hemoglobin:
    • Females: 12 - 16 g / dL
    • Males: 14 - 18 g / dL
  • Hematocrit:
    • Males: 40 - 54%
    • Females: 37 - 47%
  • MCV: 86 - 98 µm3 / cell
  • MCH: 27 - 32 µµg / RBC
  • RDW: Red Cell Distribution Width – 11.5-14
  • Platelet Count: 150,000 - 400,000 / mm3
  • WBC Differential:
    • Neutrophils: 40-75%
    • Lymphocytes: 15-45%
    • Monocytes: 1-10%
    • Eosinophils: 1-6%
    • Basophils: 0-2%

1.2. CBC Lab

Normal values are always provided by the laboratory when blood tests are ordered, as shown in figure below.

5.0 4.73 13.8 41 86 29 34
4.5-11.0 1000/uL 3.60-5.30 ml/uL 11.5-16.0 g/dL 37-47% 80-100 IL 27-34 Pg 3 g/dL1-36

12.4 10.2 158 60 29 7 4
1.5-14.5% 6.6-11.0 IL 140-400 thou/uL 50-75% 20-40% 0-8% 0-5%

1.3. Definitions of CBC Values

1.3.1. WBC

White cells seen on the peripheral smear are:

  • Neutrophils
  • Lymphocytes
  • Monocytes
  • Eosinophils
  • Basophils
  • Neutrophils help fight bacterial infections, e.g., acute pneumonia, strep throat.
  • Presence of an acute bacterial infection results in an increased neutrophil count.

  • Antibiotics will be effective in treating acute bacterial infections.
  • Lymphocytes increase in number during an acute viral infection and there is a simultaneous reduction in the neutrophil count. Antibiotics are useless against a viral infection. Influenza, the flu is a viral infection showing signs of watery eyes and a runny nose. Anti-virals will be beneficial.

  • Monocytes increase in number during acute exacerbation of chronic bacterial problems. As seen in conditions like SBE (subacute bacterial endocardititis) and tuberculosis (TB).
  • Additionally monocytes can be increased with an acute on chronic flareup of SLE or RA. Systemic lupus erythematosus (SLE), Rheumatoid arthritis (RA) are connective tissue conditions/autoimmune conditions. When these conditions are exacerbated they are associated with elevated levels of monocytes.
  • In ALL the above situations associated with an increased monocyte count, routine dental treatment must be DEFERRED by 4-6 weeks.
  • Eosinophils increase in number when there is an underlying allergy problem, e.g., hay fever, parasites, asthma; or in association with Hodgkin’s disease.
  • Antihistamines are usually prescribed.

1.3.2. Hemoglobin:

  • Carries oxygen to the tissues in the body. A reduction in the hemoglobin content is associated with anemia. Tissue hypoxia occurs in anemic patients.

1.3.3. Hematocrit:

  • This is the percentage of RBCs relative to the plasma volume.
    • Note: With a low Hb count or low HCT, less oxygen is carried to tissues leading to tissue hypoxia and anemia symptoms.

  • A Low HCT or RBC count can be due to underproduction of RBC’s by the bone marrow or overdestruction of RBC’s by the spleen.

  • If the bone marrow is depressed, we will see a low PLAT and WBC count as well as a low RBC count. This is PANCYTOPENIA. We won’t see low WBC and PLAT counts with overdestruction of RBC’s.

1.3.4. MCV:

  • Relates to the size of an individual RBC.
  • When MCV is decreased the RBC is referred to as a microcytic cell.

  • When MCV is increased, the RBC is referred to as a macrocytic or a megaloblastic cell.
  • Microcytic cells are often associated with iron deficiency anemia.
  • Macrocytic cells are often seen with vitamin B12 or folic acid deficiency anemia or Pernicious anemia.
  • Pernicious anemia is a condition affecting elderly patients and is associated with poor absorption of Vit. B12 in the stomach.
  • The gastric HCL and Intrinsic factor are very low or absent with Pernicious anemia.

1.3.5. MCH:

  • The hemoglobin content of an individual RBC.
  • It is decreased with microcytic anemia and increased in macrocytic anemia.

    • Note: When a patient loses blood due to any cause, the iron content of their blood is reduced.

  • There is a reduction of Hb.

  • The MCV and MCH decreases and a microcytic hypochromic type of anemia results due to Fe deficiency anemia.

  • Macrocytic red blood cells indicates a problem in DNA synthesis because of a deficiency in vitamin B12 or folate.

  • The MCV and MCH are increased in macrocytic anemia.

  • This increased MCV and MCH pattern is due to folate or B12 deficiency or Pernicious anemia, as discussed above.

1.3.6. MCHC:

The amount of hemoglobin in 100 mL of packed RBCs. This test has become obsolete.

1.3.7. RDW:

  • A measure of the degree of variability in RBC size in the peripheral smear.

  • RDW is increased with many anemias.
  • An increase in the RDW indicates an overabundance of immature RBC’s in the circulation and is a sign of an active bone marrow.
  • A decreased RDW indicates an underproductive bone marrow.

1.3.8. PLAT:

  • Reduction in the platelet count below 150,000/μl is referred to as thrombocytopenia.
  • Certain levels of thrombocytopenia are associated with excessive bleeding at the time of surgery.

  • We can treat dental patients with platelet counts under 150,000/μl, but not when the numbers go below 50,000/μl.
  • Platelet replacements prior to dental treatment is necessary if the counts are below 50,000/μl.
  • The patient will complain of spontaneous bleeding with platelet counts below 20,000/μl.
  • Drugs like Aspirin and Non-Steroidal Anti-inflammatory Drugs (NSAIDs), when taken over a period of time, cause decreased cohesiveness or sticking together of the platelets. This can result in excessive bleeding at the time of surgery.
  • The platelet number is not altered by these drugs.
  • Bleeding time (BT) which measures platelet function, is prolonged with thrombocytopenia.
  • These drugs cause platelet dysfunction.

1.3.9. ESR:

  • The erythrocyte sedimentation rate measures the serum levels of globulin plus fibrinogen.
  • ESR is increased in any type of infection, inflammation or neoplasm.

  • After treatment has been started, a serial reduction in ESR levels indicates effectiveness of treatment.