Skin, or dermal, punctures are most commonly done on infants, and for point-of-care testing (POCT). Micro-collection methods may also be used for adults who provide no other access for you to obtain a blood sample. **Note - these methods should only be used when a small amount of blood is required. You should also notify the laboratory technician of the method used. Most lancets are designed to puncture a certain depth and width. When performing a heel stick, the depth of penetration should be no more than 2.0 mm, with an even lesser penetration for premature babies.
Microtainer tubes are color coded exactly the same as the evacuated tubes. They are designed to reduce leakage, and each tube shows a minimum and maximum fill line. When using microtainer tubes, lithium and ammonium salts of heparin are the anticoagulants of choice. See pictures below.
Capillary tubes are disposable, narrow, plastic tubes designed for packed red cell volume (hematocrit) testing. They carry different color bands to indicate the type of additive that coats the inside. A red band indicates that it is heparin coated, and a blue band indicates there is no anticoagulant inside. Capillary tubes usually require micro-centrifugation in order to accurately complete testing. See pictures below.
Q: [Hematocrit] - An expression of the volume of red cells per unit of circulating blood
Q: [Volume] - Quantity or amount of occupied space
Q: [Centrifugation] - A process that involves the use of centrifugal force for the separation of mixtures