Blood is often collected in what capillary tubes to prevent clotting?

Blood is often collected in capillary tubes coated with an anticoagulant, such as heparin or EDTA (ethylenediaminetetraacetic acid), to prevent clotting. These tubes help preserve the sample for accurate laboratory analysis by inhibiting the coagulation process. The anticoagulant ensures that the blood remains in a liquid state, allowing for various tests to be performed without interference from clots.