A capillary sample is a blood sample collected by pricking the skin. Capillaries are tiny blood vessels near the surface of the skin.
Some blood tests are performed on blood obtained by pricking the skin of the finger, heel, or other areas 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 pricked 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.
Some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Blood transports oxygen, food, waste products, and other materials within the body. It also helps regulate body temperature. Blood is made up of a fluid called plasma and cells. Plasma contains various dissolved substances. The cellular portion consists primarily of red blood cells, but also includes white blood cells and platelets.
Because blood has multiple functions, tests on the blood or its components can provide valuable clues in the diagnosis of a multitude of medical conditions.
Capillary blood sampling offers several advantages:
There are some disadvantages to capillary blood sampling.
See the specific test.
Results vary depending on the test performed.
Capillary blood sampling is very useful when very small amounts of blood are needed or when blood is very difficult to obtain, such as in infants. Many times, however, when a larger sample is needed, the blood must be obtained from a vein.
Blood sample - capillary; Fingerstick; Heelstick
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Hayrapetian-Dorsi L. Genetics. In: Custer JW, Rau RE, eds. Johns Hopkins: The Harriet Lane Handbook. 18th ed. Philadelphia, Pa: Elsevier Mosby; 2009:chap 13.
Updated by: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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