Tufts OpenCourseware
Search
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.

WBC RBC HGB HCT MCV MCH MCHC
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



RDW MPV PLAT NEUT LYMP MONO EOS
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.