The question of whether a blood culture can be drawn from a Peripherally Inserted Central Catheter (PICC line) is frequent in healthcare settings. While the PICC line offers accessible access to central circulation, using it for blood sampling introduces variables that can compromise the accuracy of the test. The decision to use a PICC line for this purpose is highly conditional and must be weighed against the gold standard of a peripheral blood draw.
What Are PICC Lines and Blood Cultures
A PICC line is a long, thin tube inserted into a peripheral vein, typically in the arm, with its tip resting in a large central vein near the heart, such as the superior vena cava. This device provides reliable, long-term intravenous access for administering medications, fluids, or nutrition. Avoiding repeated needle sticks for patients requiring frequent treatment is a major advantage of the PICC line.
A blood culture is a laboratory test where a blood sample is placed into special bottles containing a growth medium to detect microorganisms like bacteria or fungi. The primary purpose is to diagnose a bloodstream infection, such as bacteremia or fungemia. Identifying the specific microbe helps clinicians choose the most effective antimicrobial treatment.
The Clinical Decision to Draw Cultures from a PICC
Blood cultures can be drawn from a PICC line, but this is generally discouraged for routine testing due to the significantly increased risk of contamination. Catheter-drawn cultures have been shown to have a higher contamination rate compared to peripheral venipuncture. This contamination usually happens when common skin bacteria from the catheter hub or skin surrounding the insertion site enter the sample during the collection process.
A false-positive result, caused by contamination, can lead to serious consequences, including the unnecessary administration of broad-spectrum antibiotics and prolonged hospital stays. However, there are two primary clinical scenarios where drawing from a PICC line is justified.
Peripheral Access is Impossible
The first is when peripheral access is impossible, requiring at least two blood samples to be drawn from different lumens of the central line or at different times.
Suspected Catheter-Related Bloodstream Infection (CRBSI)
The second, and most common, acceptable scenario is when a Catheter-Related Bloodstream Infection (CRBSI) is specifically suspected. A paired sample is required, meaning one blood culture set is drawn from the PICC line and a second set is drawn simultaneously from a peripheral vein. Comparing the results, particularly the time it takes for microbial growth to appear, helps determine if the catheter itself is the source of the infection. If the PICC culture bottle shows growth at least two hours earlier than the peripheral culture, it strongly suggests the infection is localized to the catheter.
Steps for Minimizing Contamination
If the decision is made to draw blood cultures from a PICC line, healthcare providers must follow strict procedural safeguards to mitigate the inherent risk of contamination. The process begins with meticulous aseptic technique, often referred to as “scrub the hub,” which involves vigorously disinfecting the catheter hub or access port with an antiseptic like chlorhexidine. This step is designed to eliminate microorganisms colonizing the external surfaces of the line and its connectors.
Before collecting the sample for culture, a discard volume of blood must be drawn and thrown away. This waste volume, typically 5 to 10 milliliters, is drawn to clear the line of any stagnant fluid, biofilm, or residual medication, which could inhibit bacterial growth or introduce contaminants. The precise volume of blood required for the culture itself is also important, as underfilling the bottles can reduce the test’s sensitivity.
Following the discard volume, blood is drawn directly into the culture bottles, and the correct order of inoculation must be observed. For most adult collections, the aerobic bottle should be filled first. This is because the collection device tubing may contain a small amount of air, and the aerobic bottle is designed to utilize this oxygen-rich environment for optimal growth. Ensuring the proper blood volume—typically 8 to 10 milliliters per bottle—and the correct sequence helps maximize the chance of an accurate result.
The Importance of Peripheral Blood Cultures
A peripheral venipuncture remains the most reliable method for diagnosing a systemic bloodstream infection. A peripheral draw involves a direct stick into a vein, typically in the arm, which bypasses the potential contamination risk associated with the indwelling catheter. The skin at the venipuncture site is sterilized just before the needle insertion, minimizing the chance of skin flora entering the sample.
This lower contamination rate provides a more accurate representation of the patient’s true bloodstream status. Official guidelines strongly recommend obtaining blood cultures via peripheral venipuncture as the default first choice whenever possible. The PICC line draw should be viewed as a necessary exception, utilized only when peripheral access is unavailable or when the goal is to specifically confirm a catheter-related infection by comparing it with a simultaneous peripheral sample.