ASCP Capillary Puncture and Dermal Collection 1 — Questions and Answers
Question 1: Which finger is the preferred site for capillary blood collection in adults?
- Thumb
- Middle or ring finger (Correct answer)
- Index finger
- Pinky finger
Correct answer: Middle or ring finger
The middle and ring fingers are preferred because they have more tissue depth and are less calloused than the thumb or index finger.
Question 2: What is the purpose of discarding the first drop of blood during capillary collection?
- It contains excess anticoagulant from the lancet
- It may be contaminated with tissue fluid that can cause erroneous results (Correct answer)
- It is required only for glucose testing per CLSI standards
- It reduces the risk of hemolysis in subsequent drops
Correct answer: It may be contaminated with tissue fluid that can cause erroneous results
The first drop may be diluted with tissue fluid released during the puncture, which can affect test results.
Question 3: Which area of the heel is recommended for capillary puncture in neonates?
- The center of the heel
- The posterior curvature of the heel
- The medial or lateral plantar surface (Correct answer)
- The dorsal surface of the foot
Correct answer: The medial or lateral plantar surface
The medial or lateral plantar surface avoids the calcaneus bone and major nerves and arteries, making it the safe zone for heel sticks.
Question 4: What is the maximum recommended puncture depth for a neonate heel stick per CLSI guidelines?
- 1.0 mm
- 1.5 mm
- 2.0 mm (Correct answer)
- 2.5 mm
Correct answer: 2.0 mm
CLSI guidelines recommend a maximum puncture depth of 2.0 mm for neonatal heel sticks to avoid hitting the calcaneus bone.
Question 5: In capillary blood collection, which specimen is collected FIRST when multiple collection devices are used?
- EDTA (lavender) tubes (Correct answer)
- Serum or non-additive tubes
- Blood gas specimens
- Slides for differential smears
Correct answer: EDTA (lavender) tubes
In capillary collection, EDTA tubes are collected first to ensure adequate anticoagulation before platelets begin to aggregate.
Question 6: Which action should be avoided when collecting a capillary blood specimen?
- Warming the puncture site beforehand
- Wiping away the first drop of blood
- Squeezing or milking the site excessively (Correct answer)
- Making the puncture perpendicular to fingerprint lines
Correct answer: Squeezing or milking the site excessively
Excessive squeezing dilutes the specimen with tissue fluid and can cause hemolysis, leading to erroneous test results.
Question 7: What is the recommended method to increase blood flow to a site before capillary puncture?
- Apply a tourniquet to the wrist
- Warm the site to approximately 42°C for 3 to 5 minutes (Correct answer)
- Have the patient hold their breath
- Apply alcohol and allow it to air dry for 30 seconds only
Correct answer: Warm the site to approximately 42°C for 3 to 5 minutes
Warming the site to 42°C for 3 to 5 minutes causes vasodilation and increases arterial blood flow into the capillary bed.
ASCP Capillary Puncture and Dermal Collection 1
Which finger is the preferred site for capillary blood collection in adults?