White-Blood-Cell Differential

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Category: Hematology.
Subcategory: White-blood-cell tests.
Material studied: Blood.
Estimated cost of test: $7.50.
Patient time for test: 5-10 minutes.
Reliability of test results: Good.
Available as home self-test? No.

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BEFORE THE TEST

Purpose of test:

• Evaluates body's capacity to resist and overcome infection.
• Detects and identifies various types of leukemia.
• Determines the stage and severity of an infection.
• Detects and assesses severity of allergic reactions and parasitic infections.

Where is test performed?

• Commercial laboratory, hospital, doctor's office.

Who performs test?

• Lab technician, nurse, doctor.

Risks and precautions:

• If tourniquet is applied on arm too long (over 1 minute), it may cause an inaccurate test result. Request another sample to be collected to ensure accuracy.

Patient preparation:

• Activity - Avoid any strenuous exercise 24 hours before test.
• Diet - No changes necessary.
• Medicines - Inform the person performing the test if you have recently taken any medications listed under Taking these drugs may affect test results.
• Disrobing - None required. Roll up sleeve only.

THE TEST

Sensory factors:

• Touching - You will feel mild discomfort when the needle is inserted into the vein or when the lancet pricks a finger, heel or ear lobe.
• Seeing - You will see the technician, nurse or doctor, the basket or tray to hold the equipment, the needles, syringes, collecting tubes and bandages.
• Feeling - Some degree of apprehension or fear is normal and should be expected. Discomfort disappears when the test is finished.
• Other senses (taste, smell, hearing) - Not affected.

Equipment used:

• Needles, syringes and heparinized collecting tubes. Sterile, disposable equipment prevents contamination or spread of infection. There is no risk of becoming infected with the hepatitis virus, AIDS virus or any other germ.

Description of test:

• Technician, doctor or nurse applies a tourniquet or blood-pressure cuff to the upper arm.
• Skin over the vein to be stuck is cleaned with alcohol or other antiseptic on a piece of cotton.
• When blood is drawn from a vein, the operator feels the vein to be used then punctures both the skin and vein in one quick stroke.
• Operator withdraws the needle and transfers sample from the collecting syringe into sterile tubes (identified with your name) before sending samples to the laboratory for analysis.
• If blood is collected from a finger, heel or ear lobe, skin over selected site is cleaned with an antiseptic. Operator quickly pierces the skin to a shallow depth, using a sterile, disposable metal lancet. Drop or two of blood produced is collected into a capillary pipette.

AFTER THE TEST

Immediate post-test care:

• Apply pressure to the puncture site with cotton provided by the laboratory.
• If a vein has been punctured, raise your entire arm over your head while applying pressure.
• Some discoloration, soreness or swelling may develop at the venepuncture site. This responds well to moist, warm compresses applied every 2 to 4 hours.

Activity after test:

• Resume taking any medications that were withheld before the test.
• Return to pretest activities right away.

Time before test results available:

• Test requires only a few minutes in the laboratory. Time before results are reported to the doctor or patient varies from a few minutes to a few days.

TEST RESULTS

Test values:

• Test results are determined by microscopic examination of white blood cells.

Normal values:

Adults:

• Neutrophils - 47.6 to 76.8%.
• Lymphocytes - 16.2 to 43%.
• Monocytes - 0.6 to 9.6%.
• Eosinophils - 0.3 to 7%.
• Basophils - 0.3 to 2%.

Boys - Age 6-18:

• Neutrophils - 38.5 to 71.5%.
• Lymphocytes - 19.4 to 51.4%.
• Monocytes - 1.1 to 11.6%.
• Eosinophils - 1% to 8.1%.
• Basophils - 0.25 to 1.3%.

Girls - Age 6-18:

• Neutrophils - 41.9 to 76.5%.
• Lymphocytes - 16.3 to 46.7%.
• Monocytes - 0.9 to 9.9%.
• Eosinophils - 0.8 to 8.3%.
• Basophils - 0.3 to 1.4%

What HIGH or INCREASED may indicate:

• Tissue destruction.
• Metabolic disorders.
• Inflammatory disease.
• Allergies.
• Serum sickness.
• Parasitic infections.
• Some skin diseases.
• Some cancers.
• Collagen disorders.
• Pernicious or hemolytic anemia.
• Excessive exercise.
• Chronic myelocytic, lymphocytic or monocytic leukemia.
• Polycythemia.
• Hodgkin's disease.
• Mastocytosis.
• Myxedema.
• Ulcerative colitis.
• Hypersensitivity disorders.
• Nephrosis.
• Viral or bacterial infection.
• Immune diseases.
• Rickettsial-collagen disease.
• Lymphomas.

What LOW or DECREASED may indicate:

• Radiation.
• Ingestion of cancer drugs or cortisone.
• Infections.
• Enlarged spleen.
• Collagen diseases.
• Vitamin B12 or folic-acid deficiency.
• Mental or physical stress.
• Cushing's syndrome.
• Hyperthyroidism.
• Ovulation or pregnancy.
• Debilitating chronic disease.
• Defective circulation in the lymphatic vessels.
• Immunodeficiency due to drugs.

Taking these drugs may affect test results:

• Anti-convulsants. >Para-aminosali-
• Capreomycin. cylic acid.
• Cephalosporins. >Paromomycin.
• Desipramine. >Penicillins.
• D-penicillamine. >Phenothiazines.
• Gold compounds. >Procainamide.
• Indomethacin. >Rifampin.
• Isoniazid. >Streptomycin.
• Methysergide. >Sulfonamides.
• Nalidixic acid. >Tetracyclines.
• Novobiocin.

Other factors that may affect test results:

• None expected.

From the Complete Guide to Medical Tests by H. Winter Griffith, M.D. © 1988 by Fisher Books; electronic rights by Medical Data Exchange.