Reliability of blood cultures collected from intravascular catheter versus venipuncture

This is a study of 130 matched venipuncture and intravascular blood cultures collected from 53 patients. In 99 cultures (76.1%), both the venipuncture and the catheter specimens were negative. There were six matched cultures yielding significant isolates: in three both the venipuncture and intravascular specimens were positive; in two only the intravascular specimen was positive; and in one only the venipuncture specimen was positive. Twenty-five cultures were positive from the intravascular specimen only, and 23 of these were classified as contaminated cultures. Thus, the contamination rate was significantly higher in the intravascular catheter blood culture specimens (P less than 0.001). These results indicate that blood culture specimens should not be routinely collected from intravascular catheters unless collection by venipuncture is impossible.