Go Back

Diagnosing catheter-related bloodstream infections

27 May 2018

80,000 central line infections occur each year in U.S.

By: Jasmin Chaudhary, MD Cascade Infectious Diseases and Infusion, LLC

View as a webpage  

About 80,000 catheter-related bloodstream infections (CRBSI) occur in the U.S. every year. It should be suspected when a bloodstream infection occurs with no other source, particularly if dealing with Staphylococcus aureus, candida species or coagulase-negative staphylococci.

The clinical criteria for diagnosing requires demonstrating there are no alternative sources of bacteremia. Blood cultures should be obtained both peripherally and from the catheter because culturing blood from catheters alone has low specificity, meaning that it is associated with a higher rate of false positive results due to high rate of colonization with skin contaminants.

Obtaining peripheral blood cultures from pediatric patients may be more challenging, but should be attempted. Please note that if the patient has a central line and a culture is obtained without obtaining peripheral blood cultures and the culture from the line is positive, regardless of whether it is thought to be reflective of colonization, it will be categorized as a central line associated blood stream infection according to the Centers for Disease Control and Prevention’s National Health Care Safety Network reporting. To clinically diagnose a CRBSI, one of the following criteria must be met:

  1. Culture of the same organism from both the catheter tip and at least one peripheral blood culture.
  2. Culture of the same organism from at least two blood samples (one from catheter hub and the other from a peripheral vein or second lumen if unable to obtain peripheral cultures) meeting differential time to positivity or criteria for quantitative blood cultures.

Differential time to positivity is something the lab can determine and means that growth from the catheter hub occurred at least two hours prior to growth from the peripheral blood. Sensitivity and specificity are 85 and 91 percent, respectively.

It is crucial that at least two sets of blood cultures be drawn peripherally by separate venipuncture. As stated above, blood cultures should not be drawn just from the catheter port as these are frequently colonized with contaminants. There is no role for routine culturing from the catheter in the absence of clinical signs and symptoms of infection, and even then, obtaining specimens from two peripheral sites is ideal. Positive cultures drawn from the central line could inadvertently be tagged with a central line associated blood stream infection that is actually representative of contamination.