Re-Re-Re-Revisiting Blood Culture Contamination

Oct. 16, 2017

Here you sit in your office, looking at the monthly blood culture contamination data with your head shaking. You ask yourself the same questions that cycle back every several months: Why does the contamination rate fluctuate between 0.5-3% but never get to 0%? Why do you always have to go after the phlebotomy and nursing teams to engage (yet, once again) them for the perfect draw and good patient care? How to effectively deal with blood culture contamination—this is literally a million-dollar question.

The teaching on blood culture contamination has not changed much in recent years. Blood culture is still one of the most important tests to diagnose sepsis and bloodstream infections. It saves lives if done properly, but suboptimal performance can lead to deleterious impacts on patient care and hospital cost of as much as $9,000 per episode of contamination. The national benchmark for blood culture contamination is 3%, and agency such as the College of American Pathologists (CAP) requires the laboratory to monitor the contamination rate and provide feedback (MIC.22630). In order to do blood culture well, the staff must be well-trained, must know the why behind the steps, and must be able to follow the procedure carefully for every single draw. Dealing with blood culture contamination is different from handling an outbreak, which most of time, has an end date. This "eternality" factor can make the monitoring and quality assurance process long, dry, and sometimes painful. It is therefore critical to build a system for easy tracking of contamination as well as to have a multidisciplinary team for feedback and improvement.

The key to success, in short, is to make everyone who is engaged in the process accountable. If no one tracks the contamination data and provides feedback on a regular basis, the key players may not realize there is a problem, and will not improve. You don't look for it—you don't find it. Some hospitals use employee identification number or specific login information for the blood draw to track contamination rates for each person collecting blood cultures. If a generic login code is shared by nursing staffs or phlebotomists, it adds another level of work to ensure the compliance of documenting the blood culture. In our hospital system, each phlebotomist has his/her own login code for blood culture. The nursing staff, on the other hand, shares the same generic code for logging into the hospital system for the draw, and they are required to handwrite their initials or employee ID on the culture bottles. This information is documented by the processors who receive the specimens in the laboratory. Weekly and monthly blood culture contamination reports are sent to ED and nursing managers as well as the phlebotomy supervisor, so feedback is provided to the frontline staff on a regular basis. It is important to have the staff "own" the process and the results—accountability breeds response-ability.

Taking a blood samplePoor technique and noncompliance to proper disinfection of the draw site are the primary reasons for blood culture contamination. Lab work without personal protective equipment (PPE), i.e., gloves in this case, is a bad idea. Courtesy S.-K. Chow.

You don't know what you don't know, so keep educating the staff. Effective education relies on a well-designed system to discuss not only the procedures and policies, but the why behind it. Before delving into the technical aspect of a blood draw, the staff needs to understand the importance of blood culture integrity, which is the why. Blood culture contamination not only brings stress and inconvenience to the patient, but it adds a financial burden to the hospital for the cost of service, diagnostic test, antibiotic, and sometimes patient isolation. Because of the false-positive result, a patient may receive unnecessary antibiotics, and delay his/her discharge. The patient may be asked to come back to the hospital for follow-up, despite a lack of symptoms. Now, back to the why again. Do you think it is apparent to the ED nursing staff that blood culture contamination will increase the laboratory cost by requiring unnecessary isolate workup, potentially including molecular blood culture assay on systems such as Verigene or Biofire, or that the technologists now have to read and workup more cultures, or that pharmacy needs to prescribe more vancomycin just in case? Maybe, but not always. It is not uncommon to see a communication link missing between the ED and the laboratory. The ED is fast-paced, but the staff has to understand that a mistake upstream, or even worse, cutting corners, can lead to subsequent adverse effects on patient care and the clinical operation. Saving 30 seconds with suboptimal disinfection of the skin during the draw may create many hours of unnecessary follow-up work due to the contamination. It is easy for the ED staff to neglect this function while focusing on other aspects of patient care, and the topic should be introduced and refreshed from time to time.

After more than 3 decades of research on blood culture, we have a lot to learn from the literature. However, to implement a new practice or instrument in any hospital system is rarely straightforward, and it often boils down to resources. Let's take the placement of phlebotomy service in the ED as an example. Studies have shown that phlebotomy draws in the ED reduce blood culture contamination and add to hospital savings in the long run. It is more efficient to train and maintain competency of a focused group. The investment on phlebotomy staffing at the ED must be justified by the test volume, better patient care, and outcome. The long-term benefit must be well explained to the hospital administration, as the idea of interdepartmental coverage and cost-benefit can be counter-intuitive. If the phlebotomy service is ad-hoc or specific to peak hours of the day, the labor division can get complicated. Patients of older age, with critical illness, or end-stage renal disease are more likely to have blood culture contamination. These "hard draws" are sometimes purposefully left for the phlebotomist. And for the availability of phlebotomy service, certain hospital systems can afford 24/7 phlebotomy service at the ED, while other systems still primarily rely on nurse draws, which have higher contamination rates due to the high staff turnover and never-ending training of the new staff. A diversion device was recently described to further lower blood culture contamination by forfeiting the first 1.5-2 ml of blood from a draw. The idea was supported by other studies, but the cost of the device is substantial and can only be justified by significant reduction of contamination from a high baseline. Furthermore, the use of a diversion device may indirectly hamper the quality of skin disinfection by the staffs, as the skin preparation now has less impact on the integrity of the blood culture. Other recommendations to reduce blood culture contamination include the use of disinfection cap and the minimization of blood draw from catheters.

Blood culture contamination is not likely to go away, but with careful practice and monitoring, it can be reduced to close to zero. Whether using traditional methods, or the latest technologies that detect bloodstream infections from fresh blood draw instead of positive blood culture, it is anticipated that this will remain a hot topic for the foreseeable future. 

The above represents the opinions of Dr. Siu-Kei (Jacky) Chow and not necessarily of the American Society for Microbiology.

Author: Siu-Kei (Jacky) Chow

Siu-Kei (Jacky) Chow
Siu-Kei (Jacky) Chow is the Technical Director of Infectious Diseases Diagnostics at MultiCare Health System in Washington. He is a diplomate of the American Board of Medical Microbiology. He is interested in emerging infectious diseases, antimicrobial resistance, workflow optimization, and drawings of microorganisms.