ASCP Capillary Puncture and Dermal Collection 2 — Questions and Answers
Question 1: Which lancet is most appropriate for a premature infant requiring a heel stick?
- A standard adult fingerstick lancet
- A safety lancet with 2.0 mm depth and 1.5 mm blade
- A retractable lancet designed for premature neonates with a depth of 0.85 mm or less (Correct answer)
- A surgical scalpel lancet for deeper access
Correct answer: A retractable lancet designed for premature neonates with a depth of 0.85 mm or less
Premature neonates have thinner skin and less tissue depth, requiring shallower lancets (0.85 mm or less) to avoid bone injury.
Question 2: Which analyte shows the greatest variation between capillary and venous blood samples?
- Sodium
- Glucose (Correct answer)
- White blood cell count
- Potassium
Correct answer: Glucose
Glucose concentrations can differ significantly between capillary and venous blood due to peripheral tissue metabolism, especially in fasting or diabetic patients.
Question 3: When performing a heel stick on a neonate, where should the puncture NOT be made?
- Medial plantar surface
- Lateral plantar surface
- Posterior curvature of the heel (Correct answer)
- Either medial or lateral plantar surface
Correct answer: Posterior curvature of the heel
The posterior curvature of the heel is avoided because it is closest to the calcaneus bone, increasing the risk of osteomyelitis and nerve damage.
Question 4: Why must alcohol be completely dried before performing a capillary puncture?
- Wet alcohol causes the lancet to slip during puncture
- Residual alcohol can hemolyze the specimen and cause a burning sensation (Correct answer)
- Alcohol contamination prevents blood from beading properly on the skin
- Alcohol activates clotting factors prematurely
Correct answer: Residual alcohol can hemolyze the specimen and cause a burning sensation
Residual alcohol hemolizes red blood cells in the specimen and causes patient discomfort at the open puncture site.
Question 5: What must be done to a capillary tube used for microhematocrit before centrifugation?
- Label it with a permanent marker on the glass
- Seal one end with clay or a plastic cap (Correct answer)
- Fill it completely to prevent air bubbles
- Wrap it in parafilm to prevent breakage
Correct answer: Seal one end with clay or a plastic cap
All capillary tubes used for microhematocrit must be sealed at one end with clay or a plastic cap to prevent leakage during high-speed centrifugation.
Question 6: A patient's finger appears cold and cyanotic before a fingerstick. What is the best action?
- Proceed with the puncture immediately to avoid delay
- Apply alcohol and wait 60 seconds before puncturing
- Warm the finger with a warm compress for 3 to 5 minutes (Correct answer)
- Switch to venipuncture instead
Correct answer: Warm the finger with a warm compress for 3 to 5 minutes
Cold, cyanotic fingers have reduced blood flow; warming the site increases local circulation to produce an adequate and representative capillary specimen.
Question 7: In the capillary order of draw, which tube is typically collected LAST?
- EDTA (lavender) tube
- Blood gas specimens
- Serum separator or plain non-additive tubes (Correct answer)
- Slides for differential smears
Correct answer: Serum separator or plain non-additive tubes
Serum and non-additive tubes are collected last in capillary collection because clotting has already begun and they are least sensitive to the timing of platelet aggregation.
ASCP Capillary Puncture and Dermal Collection 2
Which lancet is most appropriate for a premature infant requiring a heel stick?