Value of semiquantitative cultures of blood drawn through catheter hubs for estimating the risk of catheter tip colonization in cancer patients

Colonization of central catheter tips has been associated with catheter-related infections. This colonization is defined as the presence of over 15 CFU in a semiquantitative catheter tip culture performed after catheter removal. Using a simple pour-plate technique, we determined the microbial concentrations in samples of blood collected via the hubs of 205 central catheters while they were in position in 179 cancer patients. All catheters were removed within three days of blood collection via the hub and cultured semiquantitatively. We then compared the results for the hub blood cultures and catheter tip cultures. Cultures from 18% of the hub samples and 29% of the tips were positive. When a cutoff limit of 1,000 CFU/ml was used for the blood cultures, the sensitivity was 20% and the specificity was 99% for estimating catheter tip colonization. These values did not seem to be related to the underlying disease, the site of catheter insertion, or the antibiotic treatment administered at catheter removal. We conclude that, if positive, cultures of blood sampled via the catheter hub can be useful in assessing the risk of catheter colonization in cancer patients.