Specimen Handling and Processing Flashcards

A phlebotomist has collected a blood sample in a serum separator tube (SST). To ensure proper processing, what is the minimum recommended time the tube should be allowed to clot before centrifugation?

Answer: 30 minutes

Serum separator tubes (SSTs) require adequate time for the blood to fully clot before centrifugation. This ensures the formation of a stable fibrin barrier between the serum and the cellular components. According to standard laboratory procedures, the minimum recommended clotting time for an SST is 30 minutes at room temperature.

A laboratory requisition specifies that a blood specimen must be protected from light. Which of the following analytes is most likely being tested?

Answer: Bilirubin

Bilirubin is a light-sensitive analyte. Exposure to light, especially ultraviolet light, can cause it to break down, leading to falsely low test results. Therefore, specimens for bilirubin testing must be protected from light by using an amber-colored tube or by wrapping the tube in foil.

A phlebotomist is preparing several specimens for transport to a reference laboratory. One test requires the plasma to be separated from the cells and frozen. Which of the following is a critical step in this process?

Answer: Aliquot the plasma into a separate, properly labeled transport tube after centrifugation.

When a frozen plasma specimen is required, the whole blood tube (e.g., light blue, green, or lavender top) must first be centrifuged to separate the plasma from the red blood cells. After centrifugation, the plasma must be carefully removed (aliquotted) and transferred into a separate, labeled plastic transport tube before being frozen. Freezing the whole blood tube would cause hemolysis and render the specimen unusable.

Which of the following is a common reason for a laboratory to reject a blood specimen drawn for a coagulation test, such as a PT or aPTT?

Answer: The light blue top tube is underfilled.

Coagulation tests require a specific blood-to-anticoagulant ratio (9:1). The light blue top tube contains sodium citrate anticoagulant. If the tube is underfilled, the ratio of anticoagulant to blood is too high, which can lead to erroneously prolonged clotting times and inaccurate test results. This is a primary reason for specimen rejection for coagulation studies.

During centrifugation of blood specimens, what is the most important principle to follow to ensure the centrifuge operates safely and correctly?

Answer: Ensure the centrifuge is perfectly balanced by placing tubes directly opposite each other.

Balancing the centrifuge is critical for safety and proper function. Every tube placed in the rotor must be balanced by another tube of the same type, size, and fill volume placed directly opposite it. An unbalanced centrifuge can vibrate excessively, potentially causing damage to the machine and breakage of specimen tubes.

A phlebotomist is sending a refrigerated specimen to a reference lab. According to standard transport guidelines, what is the appropriate temperature range that must be maintained?

Answer: 2-8°C

Refrigerated specimens must be kept within a strict temperature range to maintain analyte stability. The universally accepted range for refrigerated medical specimens during transport and storage is 2-8°C (35.6-46.4°F). Temperatures below this can cause freezing and hemolysis, while higher temperatures can lead to degradation of the sample.