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Capillary sample How the Test is Performed:
Some blood tests may be performed on blood obtained by pricking the skin of the finger, heel, or other areas (capillary blood) and collecting a drop (or a few drops) of blood on a test strip or into a small container.
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. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding .
How to Prepare:
The preparation varies with the test performed.
How it Feels:
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing .
Risks:
- excessive bleeding
- fainting or feeling lightheaded
- hematoma (blood accumulating under the skin)
- infection (a slight risk any time the skin is broken)
- multiple punctures to locate veins
Why this Test is Performed:
Blood is used by the body for transportation of oxygen, food, waste products, and other materials within the body. It is also used for regulation of body temperature, regulation of fluids, and acid-base equilibrium. Blood is made up of a fluid portion (plasma) and a cellular portion. Plasma contains various substances dissolved in the fluid. The cellular portion consists primarily of red blood cells, but also includes white blood cells and platelets . Because blood is used for multiple functions within the blood, tests on the blood or its components may give valuable clues in the diagnosis of a multitude of medical conditions.
Capillary blood sampling offers the advantages of easy obtainment (no need to "hunt" for a vein), the ability to rotate sites, and the ability to be performed at home and with minimal training. The disadvantages are the limited amount of blood that can be obtained and the inaccuracy of capillary blood for some testing.
Normal Values:
See the specific test.
Abnormal Results:
Results vary depending on the test performed.
Cost:
The estimated cost is calculated per test, not for taking the sample. See the specific test.
Special Considerations:
Blood tests are most commonly performed on blood from a vein ( venipuncture ). The results of capillary testing may be very accurate for some tests, but for other tests they may be less accurate.
Blood is routinely drawn from newborn infants for testing. Blood is obtained by "heel stick" and collected on a special blotter paper. Routine testing includes phenylketonuria and blood type. Many hospitals include other tests such as thyroid function, hemoglobin S (sickle cell disease), or may test for other blood disorders (hemoglobinopathies). Testing can be tailored to the local population, taking into account race and ethnic background in determining what routine testing should be done.
Blood is routinely drawn from newborn infants for testing. The three circles on the special blotter paper are smears of blood. Patient information and identification is included on the paper, and is sent to the state testing laboratory. Results are available within a few days.
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