Specimen Collection and Procurement Flashcards

A patient is scheduled for a Prothrombin Time (PT/INR), a Complete Blood Count (CBC), and a glucose test. Following the CLSI recommended order of draw, which tube should be collected second?

Answer: Light Blue top (Sodium Citrate)

The correct order of draw is crucial to prevent cross-contamination of additives between tubes. According to CLSI guidelines, the sequence is: 1) Blood cultures, 2) Light Blue top (for coagulation tests like PT/INR), 3) Serum tubes (Red/Gold), 4) Heparin tubes (Green), 5) EDTA tubes (Lavender for CBC), and finally 6) Glycolytic inhibitor tubes (Gray for glucose). Therefore, the Light Blue top tube is collected second in this scenario.

A medical laboratory assistant instructs a patient on collecting a 24-hour urine specimen. Which instruction is a critical part of this procedure?

Answer: Discard the first morning void, then begin collecting all subsequent urine for 24 hours.

For a 24-hour urine collection, the procedure must start with an empty bladder. Therefore, the patient should void and discard the first morning specimen, note the time, and then collect all urine for the next 24 hours, including the first morning specimen on the following day. The collection container should be kept refrigerated or on ice. Missing any sample can invalidate the test results.

Which of the following is a primary reason for specimen rejection in the laboratory?

Answer: The specimen is unlabeled or the label information does not match the requisition.

Proper specimen identification is the most critical step in pre-analytical processing to ensure patient safety and test accuracy. An unlabeled or mislabeled specimen is a major, unacceptable error because the laboratory cannot be certain of the sample's origin. While other factors can affect specimen quality, an identification error will lead to immediate rejection.

A specimen for bilirubin testing arrives in the laboratory in a clear transport bag. The test is scheduled to be performed 2 hours after collection. What is the most likely issue with this specimen?

Answer: Bilirubin is light-sensitive and the specimen was not protected from light.

Bilirubin is a light-sensitive analyte. Exposure to light, especially ultraviolet light, causes it to break down, leading to falsely low test results. Specimens for bilirubin testing must be protected from light by using an amber-colored tube or by wrapping the tube in aluminum foil or other light-blocking material.

When collecting a blood specimen using a winged infusion set (butterfly) and an evacuated tube system for a single coagulation test (light blue top), what is the correct procedure?

Answer: Draw a discard tube before the light blue top tube.

The tubing of a winged infusion set contains air. If the light blue (sodium citrate) tube is the first or only tube drawn, this air will enter the tube first, preventing it from filling to the proper volume. This would alter the critical 9:1 blood-to-anticoagulant ratio, invalidating coagulation test results. A discard tube (a plain red top or another light blue top) must be drawn first to purge the air from the tubing.

For which of the following specimens is maintaining sterility during collection of utmost importance to ensure accurate results?

Answer: Urine for culture and sensitivity

When collecting a urine specimen for culture and sensitivity, the goal is to identify and quantify bacteria from a potential urinary tract infection. Contamination of the specimen with bacteria from the skin or surrounding environment can lead to false-positive results and inappropriate antibiotic treatment. Therefore, a sterile container and a 'mid-stream clean catch' technique are essential.