Blood Culture Contamination: A Randomized Trial Evaluating the Comparative Effectiveness of 3 Skin Antiseptic Interventions

OBJECTIVE. To determine relative rates of blood culture contamination for 3 skin antisepsis interventions-10% povidone iodine aqueous solution (PI), 2% iodine tincture (IT), and 2% chlorhexidine gluconate in 70% isopropyl alcohol (CHG)-when used by dedicated phlebotomy teams to obtain peripheral blood cultures. DESIGN. Randomized crossover trial with hospital floor as the unit of randomization. SETTING. Teaching hospital with 885 beds. PATIENTS. All adult patients undergoing peripheral blood culture collection on 3 medical-surgical floors from May 2009 through September 2009. INTERVENTION. Each antisepsis intervention was used for 5 months on each study floor, with random crossover after a 1-month washout period. Phlebotomy teams collected all peripheral blood cultures. Each positive blood culture was adjudicated by physicians blinded to the intervention and scored as a true positive or contaminated blood culture. The primary outcome was the rate of blood culture contamination for each antisepsis agent. RESULTS. In total, 12,904 peripheral blood culture sets were evaluated, of which 735 (5.7%) were positive. There were 98 contaminated cultures, representing 13.3% of all positive cultures. The overall blood culture contamination rate for the study population was 0.76%. Intent-to-treat rates of contaminated blood cultures were not significantly different among the 3 antiseptics (P = .18), yielding 0.58% with PI (95% confidence interval [CI], 0.38%-0.86%), 0.76% with IT (95% CI, 0.52%-1.07%), and 0.93% with CHG (95% CI, 0.67%-1.27%). CONCLUSION. Choice of antiseptic agent does not impact contamination rates when blood cultures are obtained by a phlebotomy team and should, therefore, be based on costs or preference.