Phlebotomy Test Special Collection Procedures 3 — Questions and Answers
Question 1: When collecting blood cultures, how should the venipuncture site be prepared to minimize contamination?
- 70% isopropyl alcohol alone, allowed to dry
- Soap and water scrub only
- Chlorhexidine gluconate or iodine tincture applied in concentric circles and allowed to dry (Correct answer)
- Povidone-iodine wiped off immediately with sterile gauze
Correct answer: Chlorhexidine gluconate or iodine tincture applied in concentric circles and allowed to dry
Chlorhexidine or iodine-based antiseptics applied in an outward concentric-circle motion and allowed to fully dry provide the best reduction in skin flora.
Question 2: In a 2-bottle blood culture set, which bottle should be inoculated first when using a winged blood collection set (butterfly needle)?
- Anaerobic bottle first
- Aerobic bottle first (Correct answer)
- Either bottle; order does not matter
- The bottle with the smaller volume requirement first
Correct answer: Aerobic bottle first
When using a butterfly set, the tubing contains air; inoculating the aerobic bottle first prevents that air from entering the anaerobic bottle.
Question 3: Which type of specimen is required for a sweat chloride test used to diagnose cystic fibrosis?
- Venous blood in a lithium heparin tube
- Sweat collected via pilocarpine iontophoresis onto gauze or filter paper (Correct answer)
- A 24-hour urine collection
- Saliva collected in a sterile cup
Correct answer: Sweat collected via pilocarpine iontophoresis onto gauze or filter paper
The pilocarpine iontophoresis method stimulates localized sweating, and the collected sweat is analyzed for chloride concentration.
Question 4: A glucose tolerance test (GTT) timed specimen drawn at the 2-hour interval must be collected within how many minutes of the scheduled time to be valid?
- ± 30 minutes
- ± 5 minutes (Correct answer)
- ± 15 minutes
- ± 45 minutes
Correct answer: ± 5 minutes
GTT specimens must be collected within ±5 minutes of the scheduled interval to ensure accurate glucose curve interpretation.
Question 5: What is the recommended minimum volume of blood to inoculate into each blood culture bottle in an adult collection?
- 1–2 mL
- 8–10 mL (Correct answer)
- 5 mL
- 15–20 mL
Correct answer: 8–10 mL
Inoculating 8–10 mL per bottle maximizes the sensitivity of blood culture by increasing the chance of detecting low-level bacteremia.
Question 6: When is an icteric (jaundiced) specimen clinically significant in special collection protocols?
- It only affects CBC results
- It can interfere with spectrophotometric assays, causing falsely elevated or decreased results (Correct answer)
- It causes hemolysis in all tube types
- It has no impact on laboratory testing
Correct answer: It can interfere with spectrophotometric assays, causing falsely elevated or decreased results
Bilirubin's yellow pigment absorbs light at wavelengths used in many chemistry assays, causing interference and inaccurate results.
Question 7: Which phlebotomy procedure is most appropriate when a patient requires serial glucose monitoring every hour during a GTT?
- Arterial line sampling
- Repeated venipuncture at a new site each hour
- Capillary fingerstick using a lancet (Correct answer)
- Indwelling peripheral IV catheter draw
Correct answer: Capillary fingerstick using a lancet
Capillary fingersticks minimize patient discomfort and vein damage during the multiple timed collections required for a GTT.
Phlebotomy Test Special Collection Procedures 3
When collecting blood cultures, how should the venipuncture site be prepared to minimize contamination?