Certified Medical Assistant (CMA AAMA)Procedures, Examinations and DiagnosticsEasy
A medical assistant needs to obtain a capillary blood sample from a newborn for a metabolic screening test. Which site is correct for this puncture?
- AThe pad of the middle finger
- BThe dorsal surface of the great toe
- CThe posterior curvature of the earlobe
- DThe lateral or medial plantar surface of the heel
Show answer & explanationAnswer & explanation
Correct answer: D. The lateral or medial plantar surface of the heel
In infants, the lateral or medial plantar heel surface is the recommended capillary puncture site because it avoids bone and nerve damage; finger sticks are not used in infants under one year old.
Why the other options are wrong
- A. Finger sticks are used in older children and adults, not newborns, due to small finger size.
- B. The toe is not an approved site; it risks bone injury and poor circulation.
- C. Earlobe puncture is not a standard site used in pediatric or neonatal capillary sampling.
Infant Heel Stick Site
For infants under 12 months, capillary punctures are performed on the plantar surface of the heel, avoiding the posterior curvature to prevent bone injury.
- Use lateral or medial plantar heel surface
- Avoid posterior curvature (risk of calcaneus injury)
- Finger sticks reserved for children over 1 year and adults
Memory trick: 'Baby's heel, not the wheel (bone)'—stick the sides, not the back.