Quantitative tip culture methods and the diagnosis of central venous catheter-related infections

The diagnostic usefulness of two quantitative catheter culture methods was compared in a prospective study of central venous and arterial catheters. The roll-plate method followed by sonication was used to culture 177 catheters from 85 patients, and the sonication method was used to culture 136 catheters from 68 patients. All patients were evaluated for catheter-related infections. Catheter-related infections were associated with ≥100 colony-forming units (CFU) isolated from catheter tips by either roll plate (p = 0.01) or sonication (p < 0.001). The sensitivity, specificity, and positive and negative predictive values of ≥10³ CFU by roll plate for catheter-related septicemia were 56%, 97%, 63%, and 96% compared with 93%, 95%, 76%, and 99%, respectively, for the same level by sonication. For central venous and arterial catheters, the sonication method can distinguish infection from contamination and is superior to the roll-plate method in that it may offer a more sensitive and predictive alternative in the diagnosis of catheter-related septicemia.