Value of differential quantitative blood cultures in the diagnosis of catheter-related sepsis.

A prospective study was performed to assess the value of differential quantitative blood cultures in the diagnosis of catheter-related sepsis when this condition is suspected on clinical grounds and to establish a reliable discriminative value for application without removal of the inserted catheter. A total of 107 central venous catheters from 64 patients were used for the study. Blood was obtained simultaneously through the suspected infected device and from a peripheral venipuncture. The catheter was removed and its tip cultured semiquantitatively. Catheter-related sepsis occurred in 17 patients. Using as cut-off value a colony count fourfold higher in blood drawn through the catheter than in simultaneously drawn peripheral blood, a sensitivity of 94%, specificity of 100% and positive predictive value of 100% were obtained. A single bacterial count greater than 100 cfu/ml in the quantitative culture of the catheter blood specimen in the presence of a positive qualitative peripheral blood culture of the same organism was also highly suggestive of catheter-related sepsis. Differential quantitative blood culture is a reliable method for the diagnosis of catheter-associated sepsis without catheter removal.