Differential Time to Positivity: A Useful Method for Diagnosing Catheter-Related Bloodstream Infections

6 January 2004 | Volume 140 Issue 1 | Pages 18-25

Background: Catheter-related bloodstream infections are associated with recognized morbidity and mortality, especially in critically ill patients. Accurate diagnosis of such infections results in proper management of patients and in reducing unnecessary removal of catheters.

Objective: To evaluate differential time to positivity as a method for diagnosing catheter-related bacteremias caused by both short-term and long-term use of central venous catheters.

Design: Prospective study design.

Setting: M.D. Anderson Cancer Center, Houston, Texas, a tertiary care cancer center.

Patients: All patients, between September 1999 and November 2000, who had the same organism isolated from blood cultures drawn simultaneously through the central venous catheter and the peripheral vein.

Measurements: Time necessary for the blood cultures from the central venous catheter and the peripheral vein to become positive, as well as other relevant patient information.

Results: 191 bloodstream infections with positive simultaneous central venous catheter and peripheral vein blood cultures were included. One hundred eight patients had catheter-related bacteremias, and 83 had non–catheter-related bacteremias. Catheter-related bacteremias were more frequently caused by staphylococci and less likely to be associated with underlying hematologic malignant conditions, neutropenia, and longer duration of hospitalization. As a diagnostic tool for catheter-related bacteremia (using a composite definition reference standard according to the Infectious Diseases Society of America guidelines), differential time to positivity of 120 minutes or more was associated with 81% sensitivity and 92% specificity for short-term catheters and 93% sensitivity and 75% specificity for long-term catheters.

Conclusion: Differential time to positivity of 120 minutes or more is highly sensitive and specific for catheter-related bacteremia in patients who have short- and long-term catheters.

Editors' Notes Context Diagnosing central venous catheter–related bloodstream infections may be difficult. Contribution This prospective study from a tertiary care cancer center examined 191 infections with the same organism detected from simultaneously drawn central and peripheral blood cultures. Catheter-tip colonization or quantitative blood cultures defined catheter-related bloodstream infection. When the culture drawn from the catheter became positive at least 120 minutes earlier than the peripherally drawn culture, the odds of catheter-related bloodstream infection increased by a factor of 5.9. Implications Differential time to positivity of at least 120 minutes between centrally and peripherally drawn blood cultures helps diagnose catheter-related bloodstream infection. –The Editors

 

Author and Article Information

From University of Texas M.D. Anderson Cancer Center, Houston, and Texas Tech University Medical School, Lubbock, Texas.

Acknowledgment: The authors thank Dr. Lyle David Broemeling, Professor, Department of Biostatistics, University of Texas M.D. Anderson Cancer Center, Houston, Texas, for statistical help and expertise.

Potential Financial Conflicts of Interest: None disclosed.

Requests for Single Reprints: Hend Hanna, MD, Department of Infectious Diseases, Infection Control and Employee Health, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard (Unit 402), Houston, TX 77030; e-mail, hhanna{at}mdanderson.org.

Current Author Addresses: Drs. Raad, Hanna, Alakech, Chatzinikolaou, and Tarrand and Ms. Johnson: Department of Infectious Diseases, Infection Control and Employee Health, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard (Unit 402), Houston, TX 77030.

Author Contributions: Conception and design: I. Raad, H.A. Hanna.

Analysis and interpretation of the data: I. Raad, H.A. Hanna.

Drafting of the article: I. Raad, H.A. Hanna.

Critical revision of the article for important intellectual content: I. Raad, H.A. Hanna.

Final approval of the article: I. Raad, H.A. Hanna, B. Alakech, I. Chatzinikolaou, M.M. Johnson, J. Tarrand.

Provision of study materials or patients: J. Tarrand.

Statistical expertise: H.A. Hanna, M.M. Johnson.

Collection and assembly of data: H.A. Hanna, B. Alakech, I. Chatzinikolaou.