Capillary and Dermal Puncture Flashcards

Which lancet depth is recommended for an adult fingerstick to ensure adequate blood collection without causing undue pain?

Answer: 1.5–2.0 mm

A lancet depth of 1.5–2.0 mm is typically sufficient for adult fingerstick collection, providing adequate blood flow while minimizing pain and avoiding deep tissue.

A capillary blood glucose result is typically considered to be which of the following compared to a venous plasma glucose?

Answer: Approximately equal to or slightly higher than venous plasma glucose

Capillary blood glucose is approximately equal to or slightly higher (up to 10–15% higher) than venous blood glucose because capillary blood contains more arterial blood with higher glucose.

Which of the following is an absolute contraindication for a fingerstick on a specific finger?

Answer: Fingers with edema or poor circulation

Fingers with edema have excess interstitial fluid that will dilute the blood sample, and poor circulation means inadequate blood flow for collection—both are contraindications.

For a neonatal PKU screening (newborn screening), the blood specimen is collected on which type of collection device?

Answer: Blood spot filter paper card (Guthrie card)

Newborn metabolic screening uses filter paper blood spot cards (Guthrie cards), where blood drops are applied to designated circles and dried for analysis.

After a fingerstick, the patient should be instructed to hold their finger:

Answer: Elevated above heart level with pressure applied

Elevating the puncture site above heart level reduces blood flow and promotes hemostasis while applying gentle pressure; dependent positioning increases bleeding.

Which micro-collection tube (Microtainer) color is used for hematology testing (CBC) in capillary collection?

Answer: Lavender/purple (EDTA)

Lavender/purple Microtainer tubes contain EDTA anticoagulant, the same additive used in full-draw lavender-top tubes for CBC and hematology testing.

Why should a capillary blood gas specimen be collected in a heparinized capillary tube and immediately sealed at both ends?

Answer: To prevent exposure to atmospheric air that would alter CO2 and O2 levels

Sealing the capillary tube immediately prevents atmospheric oxygen from entering and CO2 from escaping, which would alter blood gas values and render the specimen invalid.

A heelstick is performed on a 3-day-old full-term newborn. Which of the following actions is INCORRECT?

Answer: Puncturing the posterior curve (back) of the heel

The posterior curve of the heel is an unacceptable site because the calcaneus is very close to the skin surface there, posing a high risk of bone puncture and osteomyelitis.