Blood Culture Contamination A Clinical and Financial Burden

Abstract

Affiliation: 1. Clinical Microbiology-Immunology Laboratories and Phlebotomy Services, University of North Carolina Hospitals, Chapel Hill, North Carolina; and University of North Carolina School of Medicine, Chapel Hill, North Carolina. Received September 20, 2012; accepted September 20, 2012; electronically published November 26, 2012. 2012 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2013/3401-0003$15.00. DOI: 10.1086/668771 The study by Washer et al in this issue of the journal reminds us of the clinical and financial burden that contaminated blood cultures represent. Washer and colleagues ask a fairly simple question: of the 3 antiseptics most widely used to cleanse venipuncture sites prior to collection of blood for culture, which results in the lowest rate of contaminated blood cultures? The answer that none is superior is consistent with a recent Centers for Disease Control and Prevention (CDC) Laboratory Best Practices Guideline on practices that reduce blood culture contamination. Besides the finding that the type of antiseptic used does not influence blood culture contamination rates, 2 other practices are associated with reduced blood culture contamination rates: having blood cultures drawn by phlebotomists whose main duty is drawing blood and having blood drawn by venipuncture rather than from intravenous catheters are strongly associated with reduced rates of contamination. The finding that the type of disinfectant used does not influence the contamination rate may be at odds with the results of some previous studies, but the CDC’s systematic review of the data suggests otherwise. One of the key strengths of the study by Washer and colleagues is the use of a dedicated phlebotomy team. It is likely that training a small group of individuals to properly apply antiseptics with different dwell times contributes to the impressively low contamination rate of less than 1% regardless of antiseptic used. This rate is superior to that reported in many studies and is significantly below the American Society for Microbiology’s and College of American Pathologists’ benchmark for contaminated blood cultures, which is between 2.5% and 3%. Why are rates lower for phlebotomists than for other healthcare providers? Simply put, it is because of training, practice, resources, and professionalism. At our institution, phlebotomists routinely have a monthly blood culture contamination rate of less than 1%, as was seen in the study of Washer and colleagues. The training they receive includes one-on-one instruction by a senior phlebotomist during their initial series of blood culture collection and retraining if their individual contamination rates rise above 2%. This is not done with any other healthcare provider in a systematic manner in our institution. Phlebotomists draw the bulk of blood cultures obtained by venipuncture, so they are more practiced at this method. This is particularly key when drawing blood cultures from patients with poor venous access, who may require venipuncture of hand or foot veins, something that trained phlebotomists are comfortable doing, whereas many other healthcare providers are not. Phlebotomists also have all the supplies at hand on individual carts that travel with them, unlike other professionals, who may have to scrounge around for appropriate supplies. Finally, they take great pride in having contamination rates that are lower than those of any other professional who draws blood cultures at our institution. It is a benchmark of their worth to the institution, something of which they are well aware. Why is reducing blood culture contamination rates important? Simply put, contaminated blood cultures are expensive and put patients at risk for significant iatrogenic complications. The seminal work by Bates et al was the first to quantify the cost of a contaminated blood culture, at $4,500. This cost was due to increased length of stay, typically of 1 day; use of unnecessary antimicrobial therapy; and diagnostic testing. Subsequent studies have put this cost as high as $10,000. Let us use an illustration to understand the annual cost of contaminated blood cultures. Say that hospital A does 20,000 blood cultures annually and has a 2.5% contamination rate, while hospital B does 30,000 with a 1% contamination rate. The cost of a contaminated blood culture at each institution is $5,000. Hospital A, even though it does two-thirds the number of blood cultures, has an annual excess expense due to contaminated blood cultures of $2,500,000, while hospital B has a cost of $1,500,000. In addition, hospital A has 200 more hospital-days when a bed is not available compared with hospital B because of the increased length of stay of 1 day. In hospitals that have a chronic shortage of beds, those extra 200 hospital bed–days would be highly useful. The clinical impact of contaminated blood cultures is also