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Complete Blood Count (CBC) Normal Laboratory Study Values

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Definition:

A complete blood count (CBC) is a series of tests used to evaluate the composition and concentration of the cellular components of blood.

It measures the following:

• The number of red blood cells (RBCs)
• The number of white blood cells (WBCs)
• The total amount of hemoglobin in the blood
• The fraction of the blood composed of red blood cells (hematocrit)
• The mean corpuscular volume (MCV) — the size of the red blood cells

CBC also includes information about the red blood cells that is calculated from the other measurements:

• MCH (mean corpuscular hemoglobin)
• MCHC (mean corpuscular hemoglobin concentration)

The platelet count is also usually included in the CBC.

Purpose:

The CBC provides valuable information about the blood and to some extent the bone marrow, which is the blood-forming tissue. The CBC is used for the following purposes:

• as a preoperative test to ensure both adequate oxygen carrying capacity and hemostasis
• to identify persons who may have an infection
• to diagnose anemia
• to identify acute and chronic illness, bleeding tendencies, and white blood cell disorders such as leukemia
• to monitor treatment for anemia and other blood diseases
• to determine the effects of chemotherapy and radiation therapy on blood cell production

Preparation:

There is no special preparation needed

How the Test is Performed:

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

Normal Values:

TEST	NORMAL VALUES
Leukocyte (White Blood Cell)	X1000 cells/mm³ (µL)
Birth	9.0-30.0
24 hours	9.4-34.0
1 month	5.0-19.5
1-3 years	6.0-17.5
4-7 years	5.5-15.5
8-13 years	4.5-13.5
Adult	4.5-11.0
Neutrophils Bands	3-5% (total WBC count)
Segs	54-62%
Lymphocytes	25-33%
Monocytes	3-7%
Eosinophils	1-3%
Basophils	0-0.75%
Erythrocytes (Red Blood Cells)
Cord	3.9-5.5 million/mm³
1-3 days	4.0-6.6 million/mm³
1 week	3.9-6.3 million/mm³
2 weeks	3.6-6.2 million/mm³
1 month	3.0-5.4 million/mm³
2 months	2.7-4.9 million/mm³
3-6 months	3.1-4.5 million/mm³
0.5-2 years	3.7-5.3 million/mm³
2-6 years	3.9-5.3 million/mm³
6-12 years	4.0-5.2 million/mm³
12-18 years (male)	4.5-5.3 million/mm³
12-18 years (female)	4.1-5.1 million/mm³
Hemoglobin
1-3 days	14.5-22.5 g/dL
2 months	9.0-14.0 g/dL
6-12 years	11.5-15.5 g/dL
12-18 years (male)	13.0-16.0 g/dL
12-18 (female)	12.0-16.0g/dL
Hematocrit
1 day	48-69%
2 days	48-75%
3 days	44-72%
2 months	28-42%
6-12 years	35-45%
12-18 years (male)	37-49%
12-18 years (female)	36-46%
Mean Corpuscular Volume (MCV)
1-3 days	95-121µm³
0.5-2 years	70-86 µm³
6-12 years	77-95 µm³
12-18 years (male)	78-98 µm³
12-18 years (female)	78-102 µm³
Mean Corpuscular Hemoglobin (MCH)
Birth	31-37 pg/cell
1-3 days	31-37 pg/cell
1 week-1 month	28-40 pg/cell
2 months	26-34 pg/cell
3-6 months	25-35 pg/cell
0.5-2 years	23-31 pg/cell
2-6 years	24-30 pg/cell
6-12 years	25-33 pg/cell
12-18 years	25-35 pg/cell
Mean Corpuscular Hemoglobin Concentration (MCHC)
Birth	30-36 g Hg/dL RBC
1-3 days	29-37 g Hg/dL RBC
1-2 weeks	28-38 g Hg/dL RBC
1-2 months	29-37 g Hg/dL RBC
3 months-2 years	30-36 g Hg/dL RBC
2-18 years	31-37 g Hg/dL RBC
Reticulocyte Count
Infants	2-5% of RBCs
Children	0.5-4% of RBCs
12-18 years (male)	0.5-1% of RBCs
12-18 years (female)	0.5-2.5% of RBCs
Platelet Count
Birth-1 week	84,000-478,000/mm³
Thereafter	150,000-400,000/mm³
ERYTHROCYTE SEDIMENTATION RATE (ESR)
TEST	NORMAL VALUE
Westergren
Child	0-10 mm/hour
Adult (male)	0-15 mm/hour
Adult (female)	0-20 mm/hour
Wintrobe
Child	0-13 mm/hour
Adult (male)	0-9 mm/hour
Adult (female)	0-20 mm/hour

What Abnormal Results Mean:

High numbers of RBCs may indicate:

• Low oxygen tension in the blood
  • Congenital heart disease
  • Cor pulmonale
  • Pulmonary fibrosis
• Polycythemia vera
• Dehydration (such as from severe diarrhea)
• Renal (kidney) disease with high erythropoietin production

Low numbers of RBCs may indicate:

• Blood loss
  • Anemia (various types)
  • Hemorrhage
• Bone marrow failure (for example, from radiation, toxin, fibrosis, tumor)
• Erythropoietin deficiency (secondary to renal disease)
• Hemolysis (RBC destruction)
• Leukemia
• Multiple myeloma
• Malnutrition (nutritional deficiencies of iron, folate, vitamin B12, or vitamin B6)

Low numbers of WBCs (leukopenia) may indicate:

• Bone marrow failure (for example, due to infection, tumor or fibrosis)
• Presence of cytotoxic substance
• Autoimmune/collagen-vascular diseases (such as lupus erythematosus)
• Disease of the liver or spleen
• Radiation exposure

High numbers of WBCs (leukocytosis) may indicate:

• Infectious diseases
• Inflammatory disease (such as rheumatoid arthritis or allergy)
• Leukemia
• Severe emotional or physical stress
• Tissue damage (SUCH AS burns)

Low hematocrit may indicate:

• Anemia (various types)
• Blood loss (hemorrhage)
• Bone marrow failure (for example, due to radiation, toxin, fibrosis, tumor)
• Hemolysis (RBC destruction) related to transfusion reaction
• Leukemia
• Malnutrition or specific nutritional deficiency
• Multiple myeloma
• Rheumatoid arthritis

High hematocrit may indicate:

• Dehydration
  • Burns
  • Diarrhea
• Polycythemia vera
• Low oxygen tension (smoking, congenital heart disease, living at high altitudes)

Low hemoglobin values may indicate:

• Anemia (various types)
• Blood loss

The test may be performed under many different conditions and in the assessment of many different diseases.

Resources:

US National Library of Medicine and the National Institute of Health – Medline Plus

Encyclopedia of Surgery

Lippincott’s Review Series Pediatrics Nursing

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