Capillary Collection Tubes
Capillary blood collection tubes are thin-walled and small-diameter glass or plastic tubes that are open on both ends. They are used to collect small volumes of blood, typically from the site of a fingerstick or heelstick.
Capillary blood collection tubes fill by capillary action, the natural movement of a liquid into a small opening. Cut to predetermined lengths, each capillary tube holds a known quantity of fluid when filled. Most capillary collection tubes are made from glass, but they may also be available in plastic or plastic-coated glass for safety.
Browse a wide range of capillary blood collection tubes, devices, and accessories, including microhematocrit, Caraway, and blood gas test tubes.
Types of Capillary Blood Collection Tubes and Devices
Capillary Blood Collection Devices
Several manufacturers offer small-volume blood specimen collection tubes to which a small piece of capillary tubing or a funnel can be attached to facilitate blood collection. These tubes are available with and without the standard anticoagulants found in regular evacuated blood collection tubes.
Microhematocrit Tubes
A hematocrit measures the percentage of red blood cells compared to the entire volume of a blood sample. A hematocrit may be a routine diagnostic test but is also often used to verify the suitability of blood donors. Most blood services organizations require that donors have a minimum hematocrit level before donating a unit of blood.
A microhematocrit requires a very small amount of blood. Standard microhematocrit tubes are approximately 3 inches (75 mm) long and hold approximately 70 µL. They are coated inside with the anticoagulant heparin to prevent the blood from clotting. After sufficient blood has been collected, the tube is closed at one end using a blood tube sealer.
The microhematocrit tube is then placed into a special rotor, centrifuged to compact the red blood cells, and the percentage is read using a tube reader or scale.
Blood Gas Test Tubes
Some capillary blood collection tubes are designed specifically for collecting arterial blood for blood gas testing. They are typically made from plastic and are coated with heparin to prevent clotting. They also vary in length from approximately 2 to 7 inches (54 to 180 mm) and capacities from 80 to 230 µL.
Other Capillary Collection Tubes
Caraway tubes have a capacity of 350 µL and are used to collect capillary blood for a specific method of uric acid testing.
Natelson tubes are smaller capacity tubes (0.25 mL) that can be used to perform erythrocyte sedimentation rates (ESRs), which typically require approximately 2 mL of blood.