Phlebotomy 101: Order of Draw

Vacutainer Order of Draw

The order of draw is a crucial step in blood collection that ensures the accuracy of laboratory results. It dictates the specific sequence in which blood samples are drawn into different tubes. This order helps prevent contamination of additives between tubes, which can significantly impact test results. 

While the specific order may vary slightly depending on the laboratory, a common order of draw includes:

1. Blood Culture Bottles (if ordered): These are typically collected first to minimize the risk of contamination.

2. Light Blue Top Tubes (Sodium Citrate): Used for coagulation tests (e.g., PT, PTT).

3. Red Top Tubes (No Additive) or Gold Top Tubes (Serum Separator Tube): Used for serum chemistry tests.

4. Green Top Tubes (Heparin): Used for some chemistry tests and blood gas analysis.

5. Lavender Top Tubes (EDTA): Used for hematology tests (e.g., complete blood count - CBC).

6. Gray Top Tubes (Fluoride/Oxalate): Used for glucose and other blood sugar tests.

• By adhering to the correct order, phlebotomists minimize the risk of cross-contamination. For example, if a tube containing an anticoagulant is drawn before a tube meant for serum testing, the anticoagulant can inadvertently enter the serum tube, rendering the serum sample unusable.

• Different additives in the tubes serve specific purposes. Following the order of draw helps ensure that these additives do not interfere with the intended tests for each sample.

Blood Culture Order of Draw

Blood cultures are laboratory tests used to detect the presence of microorganisms, such as bacteria, fungi, or yeast, in the bloodstream. These tests are crucial for diagnosing infections like sepsis, which can be life-threatening.

Order of Draw for Blood Cultures

Blood cultures are always drawn first in the order of draw for blood collection. This strict adherence to the order is critical for the accuracy of the test results.

Why is this Order Crucial?

• Blood culture bottles are designed to maintain a sterile environment for the growth of any microorganisms present in the blood. Drawing other blood tubes before the culture bottles can introduce additives from those tubes (like anticoagulants) into the culture media. This contamination can interfere with the growth of microorganisms, leading to inaccurate or misleading results.

• Drawing blood culture bottles first helps preserve the sterility of the collection process and ensures the integrity of the test results.

Microtainer Order of Draw

Microtainer tubes are small, specialized tubes used to collect small volumes of blood, typically from a capillary puncture (finger poke). They differ significantly from standard vacutainer tubes in several ways: 

• Microtainer tubes are much smaller than vacutainer tubes and are designed to collect very small blood samples.

• Microtainer tubes are used for capillary blood collection, while vacutainer tubes are typically used for venipuncture (drawing blood from a vein)

• Microtainer tubes are used for a variety of tests that require small blood samples, such as blood glucose monitoring, hemoglobin and hematocrit tests, some newborn screening tests, and blood alcohol level tests.

• Minimize Additive Contamination: It is important to minimize the risk of cross-contamination between tubes containing different additives.

Order of Draw for Microtainers:

1. Lavender Top Tube (EDTA)

2. Green Top Tube (Lithium Heparin)

3. Mint Green Top Tube (Lithium Heparin & Gel for Plasma Separation)

4. Gold Top Tube (Clot Activator & Gel for Serum Separation)

5. Red Top Tube (No Additive)