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Catheter-Associated Bacteremias: Timing Is Everything
A new technique could improve diagnosis of catheter-related bacteremia, without necessitating catheter removal.
More than 200,000 cases of catheter-related bloodstream infection (CRBSI) occur annually in the U.S. Accurate diagnosis of CRBSI has required quantitative blood cultures, which are labor-intensive and costly, or catheter removal. Researchers in Texas recently examined another diagnostic technique, differential time to positivity, in 191 cancer patients in whom a central venous catheter blood culture yielded the same organism as did a simultaneous peripheral vein blood culture.
One hundred eight episodes met the study definition of CRBSI (based on either quantitative blood culture results or semiquantitative catheter-tip culture data), and 83 did not. Positivity in the catheter-drawn culture 
120 minutes earlier than in the peripheral vein culture was more likely in patients with a CRBSI than in those with another bloodstream infection (P<0.001). This approach showed 89% sensitivity and 83% specificity. Results were comparable between short-term (<30 days) and long-term (30 days) catheters. However, analysis of 18 episodes in patients receiving antibiotics when blood cultures were drawn revealed a sensitivity of only 28% but a specificity of 91%.
Comment: As an editorialist notes, more-accurate diagnosis of catheter-related sepsis is urgently needed. This large study confirms earlier work demonstrating an association between time of culture positivity and source of infection. Many clinical laboratories already use blood culture systems that record time of positivity; instituting the differential positivity technique would not be difficult and could avoid catheter removal.
— Neil M. Ampel, MD
Published in Journal Watch Infectious Diseases February 2, 2004
Citation(s):
Raad I et al. Differential time to positivity: A useful method for diagnosing catheter-related bloodstream infections. Ann Intern Med 2004 Jan 6; 140:18-25.
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- Medline abstract (Free)
Farr BM. Catheters, microbes, time, and gold standards. Ann Intern Med 2004 Jan 6; 140:62-4.
- Original article (Subscription may be required)
- Medline abstract (Free)