Equipment, Tubes, and Additives Flashcards

A phlebotomist is preparing for a routine venipuncture on an adult patient with good veins. Which of the following needle gauges is most commonly used for this type of procedure?

Answer: 21 gauge

The 21-gauge needle is the standard and most commonly used needle for routine venipuncture on adult patients with normal veins. It provides a good balance between patient comfort and blood flow rate, minimizing the risk of hemolysis. 16 and 18-gauge needles are larger and typically used for blood donation, while 25-gauge needles are smaller and reserved for difficult draws, such as on pediatric or geriatric patients.

A physician orders coagulation studies, including a Prothrombin Time (PT) and Activated Partial Thromboplastin Time (aPTT). Which color top tube should the phlebotomist select for this collection?

Answer: Light Blue

Light blue top tubes contain the anticoagulant sodium citrate, which is the required additive for most coagulation testing, including PT and aPTT. Sodium citrate works by binding calcium to prevent the blood from clotting, which is essential for accurate coagulation study results. The fill volume in this tube is critical to maintain the correct blood-to-anticoagulant ratio.

Which of the following additives is an anticoagulant that works by binding calcium, thereby inhibiting the coagulation cascade?

Answer: EDTA

Ethylenediaminetetraacetic acid (EDTA) is an anticoagulant that prevents blood from clotting by chelating (binding) calcium ions, which are essential for the coagulation process. This mode of action makes it ideal for hematology studies where preserving the morphology of blood cells is crucial. Silica and thrombin are clot activators, while heparin inhibits thrombin formation.

A phlebotomist is tasked with drawing blood for a Complete Blood Count (CBC), a chemistry panel (serum), and a coagulation test. What is the correct CLSI-recommended order of draw for these tests?

Answer: Light Blue tube, Serum tube, Lavender tube

The correct Clinical and Laboratory Standards Institute (CLSI) recommended order of draw is: 1. Coagulation tube (Light Blue), 2. Serum tube (e.g., Red, Gold), and 3. EDTA tube (Lavender). This order prevents cross-contamination of additives between tubes. For example, drawing the EDTA tube before the serum tube could lead to falsely decreased calcium levels in the chemistry panel.

A phlebotomist needs to collect a sample for glucose testing, and there may be a delay in processing. Which tube contains a glycolytic inhibitor to preserve the glucose levels in the sample?

Answer: Gray top tube

The gray top tube contains sodium fluoride, which is a glycolytic inhibitor that prevents the breakdown of glucose (glycolysis) by blood cells. It also typically contains potassium oxalate, an anticoagulant. This combination ensures the glucose concentration remains stable for an extended period, which is crucial for accurate glucose testing when processing is delayed.

During a venipuncture procedure, which piece of equipment is used to make the veins more prominent and easier to locate by restricting venous blood flow?

Answer: Tourniquet

A tourniquet is a constricting band applied to the arm, typically 3-4 inches above the venipuncture site. Its purpose is to temporarily restrict venous blood flow, which causes the veins to distend (swell), making them easier to palpate and puncture.