Qualitative intravascular catheter tip cultures do not predict catheter-related bacteremia

During a 5-month period, we evaluated the sensitivity, specificity, and predictive value of qualitative cultures of intravenous catheters submitted to a university hospital microbiology laboratory. Of 36 catheters submitted for culture from nonseptic patients, 10 (28%) grew one or more microorganisms on qualitative culture. Of 44 catheters cultured from septic patients, 20 (45%) grew one or more microorganisms, but only 5 grew microorganisms that also were isolated from blood cultures. The sensitivity, specificity, and positive predictive values for catheter-related bacteremia were 71%, 96%, and 17%, values similar to those reported for quantitative methods. Although acceptable in terms of sensitivity and specificity, the very low positive predictive value suggests that catheter-related bacteremia cannot be predicted reliably by this test. We conclude, therefore, that nonstandardized qualitative IV catheter cultures have minimal value as predictors of bacteremia and recommend that they not be performed in clinical microbiology laboratories.