Venous Blood Collection
Accurate laboratory results begin with appropriate specimen collection. Most blood specimens are obtained using standard venipuncture technique. Main Line Health Laboratories supplies clients with Vacutainer® brand collection tubes. Tube types are identified by stopper color. In certain instances the use of Serum Separator Tubes (SST®) is unacceptable. Prior to collection, consult the specific test ordered to determine the proper tube type and specimen volume required.
Main Line Health Laboratories provides the following standard procedure for venous blood collection.
Venipuncture procedure when evacuated tube system (Vacutainer®) is used
- Thread the appropriate needle into the holder until it is secure, using the needle sheath as a wrench.
- Before using, tap all tubes that contain additives to ensure that all the additive is dislodged from the stopper and the wall of the tube.
- Use a sterile blood collection tube. When drawing blood for cultures, wipe the stopper with a suitable antiseptic solution. Check the stopper to make certain it is dry before performing the venipuncture.
- Insert the blood collection tube into the holder and onto the needle up to the recessed guideline on the needle holder. Avoid pushing the tube beyond the guideline because a premature loss of vacuum may result. The tube will retract slightly. Leave it in this position.
- Make sure the patient's arm or other venipuncture site is in a downward position to prevent reflux.
- Grasp the patient's arm firmly. The phlebotomist's thumb should be used to draw the skin taut. This anchors the vein. The thumb should be one or two inches (2.5 cm or 5.0 cm) below the venipuncture site.
- With the bevel up, line up the needle with the vein and puncture the vein. Grasp the flange of the needle holder and push the tube forward until the end of the needle punctures the stopper. Blood can now be observed filling the tube. Maintain the tube below the site when needle is in the vein.
- Remove the tourniquet as soon as blood flow is established. Once the draw has started, do not change the position of the tube until it is withdrawn from the needle. During the procedure, do not allow the contents of the tube to contact the stopper. Movement of the fluid back and forth in the tube can cause back-flow of blood into the venous system and possible adverse patient reaction.
- Keep constant, slight forward pressure (in the direction of the needle) on the end of the tube. This prevents release of the shut-off sheath and stopping of blood flow. Do not vary pressure or reintroduce pressure after completing the draw.
- For tubes containing anticoagulant (i.e., light blue and lavender top) fill the tube until the vacuum is exhausted and blood flow ceases. This will ensure that there is a correct ratio of anticoagulant to blood. It is normal for the tube not to be completely filled.
- When the blood flow ceases, remove the tube from the holder. The shutoff sheath re-covers the point, stopping blood flow until the next tube is inserted.
- Mix immediately after drawing each tube that contains an additive by gently inverting the tube five to 10 times. To avoid hemolysis, do not mix vigorously.
- To obtain additional specimens, insert next tube into holder and repeat procedure from step nine.
Specimens for therapeutic drug monitoring
Patient specimens for therapeutic drug monitoring or other toxicological studies should not be collected in a Serum Separator or SST® tube. The polymer used in this collection tube may bind with certain drugs. This will result in falsely decreased patient results. Unless otherwise specified in the Directory of Services, these specimens must be collected in a standard non-gel blood collection tube (red top). Prior to collection you should consult the specific test ordered to determine the proper tube type and specimen volume required.