The skin contains bacteria that are considered normal flora. If the skin is not properly disinfected prior to blood collection for a culture, these bacteria could be introduced into the specimen and contaminate the culture. In blood, however, these same organisms can be the true cause of the infection. The only way to differentiate between a contaminant and a true pathogen is to decrease the possibility of contaminants entering the collected sample by using aseptic collection techniques.
The aseptic techniques must be employed when collecting a blood culture:
- Disinfect the top of the blood culture vials with 70% isopropyl alcohol, and allow them to dry.
- Palpate the vein and identify the venipuncture site.
- Cleanse the venipuncture site with 70% isopropyl alcohol.
- When the skin is dry, continue to disinfect the skin surrounding the venipuncture site by applying the primary disinfectant that is required by your laboratory's blood culture collection procedure. Tincture of iodine, chlorhexidine gluconate, or povidone/ 70% alcohol combo are considered the most effective antiseptics for blood culture now.
- This primary disinfectant should be allowed to dry or sit for the amount of time required by the laboratory's procedure before proceeding with the venipuncture. This will ensure adequate disinfection.
- Wear a sterile glove if you need to re-palpate the vein after disinfecting the venipuncture site.
A false-positive blood culture may result from insufficient disinfection of the venipuncture site or from re-palpating a vein after disinfection.
