A blood sample is a small portion of blood collected for laboratory analysis. These tests provide insight into a person’s overall health, helping to diagnose diseases, monitor chronic conditions, and evaluate treatment effectiveness. Blood analysis reveals abnormalities in blood cells, hormones, enzymes, and other substances, offering valuable insights into organ function. The integrity of the specimen directly impacts the accuracy of diagnostic information, making standardized collection procedures by trained professionals essential.
Patient and Site Preparation
Preparation begins with confirming the patient’s identity using at least two unique identifiers, such as their full name and date of birth, to match them with the lab request. Pre-test requirements, like fasting for a lipid panel, must be verified, as dietary intake can significantly alter test results.
The collector must assemble all necessary equipment, including tubes, needles, and antiseptics, to minimize the time needed for the draw. Proper hand hygiene is performed, and clean gloves are donned to maintain a sterile environment. The patient is positioned comfortably, typically with their arm extended and supported on a flat surface.
For venipuncture, a suitable vein is located, often in the antecubital fossa. A tourniquet is applied three to four inches above the site to restrict venous flow, making the veins more prominent. The area is meticulously cleansed with an antiseptic, such as 70% isopropyl alcohol, using a circular motion from the center outward. The antiseptic must be allowed to air dry completely, as residual alcohol can contaminate the sample and cause stinging.
Understanding Collection Techniques
Venipuncture is the standard technique for obtaining larger blood volumes using an evacuated tube system. After site preparation, the vein is anchored by pulling the skin taut below the puncture site. The needle, held bevel-up, is inserted into the vein at a shallow angle, typically between 15 and 30 degrees, to minimize trauma.
Once the needle is positioned, collection tubes are inserted into the holder, allowing the vacuum to draw the blood. Tubes must be filled in a specific sequence, known as the “order of draw,” to prevent cross-contamination by chemical additives. This sequence ensures accurate results; for example, anticoagulant tubes are drawn after sterile blood culture bottles but before tubes with clot activators.
Capillary collection, or fingerstick, is used when only a small volume of blood is needed, such as for point-of-care testing. This method uses an automated lancing device to make a controlled, shallow puncture on the side of the fingertip. For infants under six months, a heel stick is performed on the medial or lateral plantar surface of the heel, avoiding the bone.
The first drop of blood is wiped away because it may contain excess tissue fluid that could dilute the sample. Subsequent drops are collected into micro-collection tubes, often by gently applying moderate pressure to the surrounding area. Avoid excessive squeezing or “milking” the site, as this can cause hemolysis (rupture of red blood cells) and compromise test results. Once collected, the lancet is disposed of in a sharps container, and pressure is applied to the site.
Handling and Post-Procedure Care
As soon as the collection is complete, the needle is safely withdrawn, and firm pressure is applied to the puncture site with a clean gauze pad. The collector must activate the needle’s safety mechanism and discard the unit into a designated sharps container to prevent accidental needlesticks. The patient is instructed to maintain pressure for one to two minutes, or longer if they are taking blood-thinning medication.
The collected tubes must be immediately and clearly labeled at the bedside with the patient’s name, medical record number, and the date and time of collection. Tubes containing additives, such as anticoagulants, require gentle inversion—typically five to eight times—to ensure the blood thoroughly mixes. Vigorous shaking can cause hemolysis and lead to sample rejection.
After confirming that the bleeding has stopped, a bandage is applied to the site. The patient is advised to avoid strenuous activity or heavy lifting with that arm for the remainder of the day to prevent bruising or re-bleeding. Patients should monitor the site for complications like excessive swelling, persistent pain, or warmth, which warrant contacting a healthcare provider.