Advanced Phlebotomy Practice Test

Newborn heel-stick sampling for screening is done to obtain a clean capillary blood sample while minimizing injury and contamination. Use the plantar surface of the heel as the puncture site, selecting the soft tissue area rather than the edge or thigh. Warm the heel first to improve blood flow, then puncture to a shallow depth of about 1.0–2.0 mm to avoid hitting bone or causing tissue damage. Collect the blood onto filter paper (Guthrie card) or into the specified microtubes per protocol, ensuring the sample fully saturates the required area. Do not milk or squeeze the site after puncture, because this can introduce tissue fluid and dilute the sample, leading to inaccurate results. Follow the protocol for drying and handling the specimen before transport.

Puncturing the lateral edge at a greater depth risks bone or nerve injury and is not recommended; milking the site is discouraged for sample quality reasons; using a fingerstick or puncturing the thigh at a much greater depth is not appropriate for standard newborn screening.