Sites of blood collection and topical disinfectants associated with contaminated cultures: An ambidirectional cohort study.

Background: We aimed to determine whether puncture sites for blood sampling and topical disinfectants are associated with rates of contaminated blood cultures in the emergency department (ED) of a single institution.

Methods: This single-center, ambidirectional cohort study of 548 consecutive patients ≥20 years of age was performed in the ED of a university hospital in Japan over a 13-month period. Pairs of blood samples were collected for aerobic and anaerobic cultures from patients in the ED. Physicians selected puncture sites and topical disinfectants according to their personal preference.

Results: Potential contamination was identified in 110 of the 548 patients (20.1%). One hundred fourteen (20.8%) patients showed true-positive results for bacteremia, and 324 (59.1%) patients showed true-negative results. Multivariate analysis revealed more frequent contamination when puncture sites were disinfected with povidone-iodine (PVI) than with alcohol/chlorhexidine (ACHX) (adjusted risk difference, 19.1%; 95% confidence interval [CI]), 15.7-22.6;  < 0.001). In terms of blood collection sites, femoral and central venous (CV) catheter with PVI disinfection showed more frequent contamination than venous sites with ACHX (adjusted risk differences: 26.6%, 95% CI 21.3-31.9,  < 0.001 and 41.1%, 95% CI 22.2-59.9,  < 0.001, respectively).

Conclusion: Rates of contaminated blood cultures were significantly higher when blood was collected from the CV catheter or femoral sites with PVI as the topical disinfectant.