Free NCMA Basic Laboratory Procedures and Specimen Handling Questions and Answers 1 — Questions and Answers
Question 1: When performing a venipuncture, which color-topped tube should be drawn first if blood cultures are not ordered?
- Lavender
- Light Blue (Correct answer)
- Red
- Green
Correct answer: Light Blue
Following the standard order of draw to prevent cross-contamination of additives, the light blue top tube is drawn first after blood cultures. This tube contains sodium citrate and is used for coagulation studies, which are sensitive to other additives.
Question 2: What is the additive in a lavender-topped tube and what is its purpose?
- Sodium Citrate, to prevent coagulation
- Heparin, to inhibit thrombin formation
- EDTA, to prevent clotting by binding calcium (Correct answer)
- Clot activator, to promote blood clotting
Correct answer: EDTA, to prevent clotting by binding calcium
The lavender (or purple) top tube contains the anticoagulant ethylenediaminetetraacetic acid (EDTA). EDTA works by binding to calcium in the blood, which prevents clotting and preserves the shape and structure of blood cells for hematology tests like a CBC.
Question 3: A medical assistant is instructing a patient on how to collect a clean-catch midstream urine specimen. Which instruction is correct?
- Collect the very first part of the urine stream.
- Wipe the area, begin to urinate in the toilet, then collect the sample. (Correct answer)
- Fill the container to the very top.
- No special cleaning is needed before collection.
Correct answer: Wipe the area, begin to urinate in the toilet, then collect the sample.
A clean-catch midstream specimen requires careful cleansing of the genital area to prevent contamination. The patient should begin urinating into the toilet, then move the collection cup into the stream to collect the sample, and finally finish urinating in the toilet.
Question 4: When is the most appropriate time to label a patient's specimen container?
- Before entering the patient's room to save time.
- After returning to the laboratory.
- Immediately after collection, in front of the patient. (Correct answer)
- At the end of the day when all specimens are gathered.
Correct answer: Immediately after collection, in front of the patient.
To prevent errors, specimen containers must be labeled immediately after collection, in the presence of the patient. Pre-labeling containers or labeling them after leaving the room increases the risk of misidentification and medical errors.
Question 5: What is the purpose of inverting a blood collection tube after it is filled?
- To prevent the blood from hemolyzing.
- To ensure proper mixing of the additive and the blood. (Correct answer)
- To cool the specimen down more quickly.
- To release the vacuum inside the tube.
Correct answer: To ensure proper mixing of the additive and the blood.
Tubes with additives, such as anticoagulants or clot activators, must be gently inverted a specific number of times. This action ensures that the additive is thoroughly mixed with the blood specimen to function correctly, either by preventing clotting or promoting it.
Question 6: Which of the following is an example of a CLIA-waived test that a medical assistant might perform?
- Blood culture analysis
- PAP smear microscopy
- Urine dipstick test (Correct answer)
- Complete Blood Count (CBC) with differential
Correct answer: Urine dipstick test
CLIA-waived tests are simple laboratory examinations and procedures that have a low risk for an incorrect result. A urine dipstick test is a common example, as it is simple to perform and interpret. Blood cultures and PAP smears are complex tests requiring certified laboratories.
