Final answer:
A phlebotomist should use a capillary stick to collect a blood specimen from a 3-year-old for a coagulation test. The sample will be collected into a tube containing sodium citrate and then analyzed in a medical laboratory.
Step-by-step explanation:
The method a phlebotomist should use to collect a specimen from a 3-year-old for a coagulation test involves a capillary stick, which is the appropriate technique for small children or when only a small quantity of blood is needed. The capillary stick is commonly performed on the finger, earlobe, or heel (in the case of infants). For a coagulation test, which requires plasma, the blood would typically be collected into a tube containing an anticoagulant such as sodium citrate, to prevent clotting before the test.
After collection, the sample is taken for analysis to a medical laboratory, where professionals like medical technologists (MT) or clinical laboratory technologists (CLT) perform the necessary tests, including coagulation panels, to help diagnose or monitor different conditions.