Written by Amanda Mathews
In this multicenter prospective diagnostic study, the proportion of contaminated blood cultures obtained from arterial catheters was noninferior to blood cultures obtained via venipuncture.
A stick in the artery and a stick in the vein
This study included 590 critically ill ICU patients across five hospitals in Japan. The indication for blood cultures and the site of blood culture collection was at the discretion of each institution. Paired blood cultures were eligible if one was drawn via arterial catheter and one via peripheral venipuncture within 30 minutes of one another. Two infectious disease specialists assessed the paired blood cultures and determined if positive culture results were true positives or false positives. Their primary measure was contamination proportion (# false positives/total culture collections).
Their main analysis was a noninferiority comparison between the contamination proportion of blood cultures drawn from arterial catheter versus venipuncture. The non-inferior margin was set at +2.0%. Of the 290 paired samples, 6.9% (41/590) were judged to have a true positive bloodstream infection. The contamination proportion was 0.34% (2/590) from arterial catheters and 0.70% (4/590) from venipuncture. The difference in contamination proportion was -0.3% and the upper limit of the 95% CI did not exceed the predefined margin of +2.0% which established noninferiority of blood cultures drawn from arterial catheters.
A limitation in this study was that only hospitals that had already satisfied a low blood culture contamination target rate (<3%) were included, which limits generalizability. Only 1.9% of arterial catheters were placed in the femoral artery, and about 20% of the arterial catheters were placed in the ED.
How will this change my practice?
The low rate of ED obtained blood cultures and femoral artery catheter samples in this study makes it hard to generalize to my practice in the ED. I will consider obtaining a set of blood cultures from a clean radial arterial catheterization site if unable to obtain venous access on a patient in a timely manner.
Contamination of Blood Cultures From Arterial Catheters and Peripheral Venipuncture in Critically Ill Patients: A Prospective Multicenter Diagnostic Study. Chest. 2023 Jul;164(1):90-100. doi: 10.1016/j.chest.2023.01.030. Epub 2023 Jan 30.