What is the role of Purple Cap Blood Collection Tubes?

The purple cap blood collection tubes, called EDTA tubes, are crucial in medical diagnostics and laboratory testing. These tubes are designed to collect blood samples for various analyses, particularly those requiring haematological evaluations. This comprehensive overview will explore the purpose, composition, applications, and handling of purple cap blood collection tubes.

Purple Cap Blood Collection Tube

Purple blood collection tubes usually refer to vacuum tubes containing ethylenediaminetetraacetic acid (EDTA) anticoagulant. It mainly has the following functions:

Blood cell analysis

Routine blood test

It can prevent blood coagulation and maintain the original form of blood cells. In routine blood tests, laboratory professionals can accurately detect the number, size, morphology, and other parameters of red blood cells (RBC), white blood cells (WBC), and platelets (PLT).

The detection of red blood cell-related indicators is also critical. It can ensure that red blood cells do not aggregate or deform during the test process to accurately measure parameters such as the mean volume (MCV) of red blood cells, mean haemoglobin content (MCH) and mean haemoglobin concentration (MCHC), which are crucial for diagnosing the type of anaemia (such as iron deficiency anaemia, megaloblastic anaemia, etc.).

Blood cell morphology examination

For some examinations that require observation of blood cell morphology, blood collected by purple blood collection tubes is an ideal sample.

When a healthcare professional suspects a blood system disease, such as leukemia or myelodysplastic syndrome, they can observe a blood smear under a microscope to check for abnormal changes in the morphology of blood cells.

Other blood tests

Some blood rheology tests

In some blood rheology studies, blood collected by purple tubes can be used to test blood fluidity, viscosity, and other properties. Because it can maintain the integrity of blood cell components and avoid changes in blood properties caused by activation of coagulation factors, it can more accurately reflect the actual rheological state of blood in the body. However, not all blood rheology tests use purple blood collection tubes, which depends on the requirements of the test items.

Which trace elements are suitable for purple blood collection tubes?

Purple blood collection tubes mainly contain ethylenediaminetetraacetic acid (EDTA) anticoagulant, which has specific applications in trace element detection.

Calcium (Ca) detection

Calcium is an essential element in the human body and is crucial in many physiological processes, such as bone development, nerve conduction, and muscle contraction. EDTA in purple blood collection tubes can chelate calcium in the blood. During the test process, the chelated calcium can be released for testing through appropriate methods.

Magnesium (Mg) detection

Magnesium regulates the activity of various enzymes in the body, energy metabolism and other processes. Blood collected by EDTA anticoagulated purple blood collection tubes can be used to detect magnesium.

Zinc (Zn) detection

Zinc is a component of many enzymes and impacts the body’s immune function, growth and development. When using high-precision detection methods such as inductively coupled plasma mass spectrometry (ICP-MS) to detect serum zinc content, blood collected by purple blood collection tubes can provide a suitable sample.

Who are the populations that apply to purple blood collection tubes in hospitals?

People with general health examinations

Purple blood collection tubes are very suitable for people who undergo routine health examinations. For example, healthcare professionals can use purple blood collection tubes to collect blood samples during routine blood examinations and physical exams for both adults and children. It can provide accurate blood cell counts (such as red blood cells, white blood cells, and platelets) and related morphological information to help determine whether the examinee has anaemia, infection or potential problems with the blood system.

Patients with suspected blood system diseases

When patients have unexplained anaemia symptoms, such as pale complexion, dizziness, fatigue, etc., blood collected by purple blood collection tubes is critical for accurate diagnosis. Doctors can determine whether it is iron deficiency anaemia, megaloblastic anaemia or other types of anaemia by performing routine blood tests and blood cell morphology observations on blood samples.

Purple blood collection tubes can provide samples for blood smear examination and cell count for patients suspected of leukaemia. The number and morphology of white blood cells in the blood of leukaemia patients usually change abnormally.

By using purple blood collection tubes to collect blood, laboratory technicians can make blood smears in time to observe whether the white blood cells have increased primitive cells and abnormal cell morphology (such as irregular nucleus morphology, abnormal particles in the cytoplasm, etc.), providing strong evidence for the early diagnosis of leukaemia.

Patients with infectious diseases

White blood cell count and classification are essential diagnostic indicators in infectious diseases. Blood collected by purple blood collection tubes can detect changes in white blood cells. For example, in bacterial infections, the total number of white blood cells usually increases, and the proportion of neutrophils increases; in viral infections, the total number of white blood cells may be average or slightly lower, and the proportion of lymphocytes may increase.

Patients who need long-term blood monitoring

Some patients with chronic diseases, such as chronic renal failure, may need long-term monitoring of blood routine tests and trace elements in the blood. Purple blood collection tubes can meet this long-term monitoring needs because it can ensure that the quality of each blood sample collected is relatively stable, the anticoagulation effect is good, and it is conducive to accurately comparing the test results at different time points.

What Are Purple Cap Blood Collection Tubes?

Purple cap blood collection tubes serve as vacuum-sealed containers that hold the anticoagulant ethylenediaminetetraacetic acid (EDTA). This anticoagulant is essential for preventing blood clotting during the collection and processing of samples. The manufacturer typically makes the tubes from plastic or glass, designing them to maintain the integrity of the blood sample for accurate laboratory analysis.

Primary Uses of Purple Cap Tubes

These tubes primarily serve haematology tests, which study blood and its components. Some of their critical applications include:

Complete Blood Count (CBC)

A CBC is one of the most commonly ordered blood tests. It provides a detailed breakdown of red blood cells, white blood cells, platelets, haemoglobin levels, and hematocrit.

Purple cap tubes preserve cellular components, allowing accurate counts and analysis.

Blood Smears and Morphology Studies

Blood smears allow researchers to examine the shape, size, and structure of blood cells under a microscope.

Thanks to EDTA, the blood cells remain intact, providing reliable results for diagnosing conditions like anaemia, infections, and blood cancers.

Erythrocyte Sedimentation Rate (ESR)

While specialized tubes are commonly used for ESR tests, you can sometimes use purple cap tubes in specific methods to measure the rate at which red blood cells settle at the bottom of a tube.

DNA and Molecular Testing

In some cases, laboratories use purple cap tubes for genetic or molecular testing because EDTA preserves the quality of the DNA in the blood.

Why Are Purple Cap Tubes Critical for Hematology?

Haematology tests depend on the accurate preservation of blood cells, and purple cap tubes are specifically designed to achieve this. Here’s why they’re essential:

• Minimal Hemolysis: EDTA minimizes the destruction of red blood cells, ensuring test accuracy.
• Prevents Platelet Aggregation: By keeping blood in its natural, uncoagulated state, the tubes prevent clumping of platelets, which is essential for platelet counts.
• Stable Over Time: Samples collected in EDTA tubes remain stable for extended periods, allowing labs to process them without significant degradation.

Practices for Using Purple Cap Tubes

Proper handling of EDTA tube use purple cap tubes is crucial to ensure accurate test results. Here are a few tips:

1. Fill to the Correct Volume: Underfilling or overfilling the tube can affect the blood-to-EDTA ratio, leading to inaccurate results.
2. Mix Gently: After collecting the blood, invert the tube 8-10 times to ensure that the EDTA mixes evenly with the blood.
3. Store Properly: Keep the tube at the recommended temperature to preserve the sample until testing.

Conclusion

Purple cap blood collection tubes are indispensable tools in modern medical laboratories. Their ability to prevent coagulation while preserving sample integrity makes them ideal for various diagnostic tests. Understanding their role enhances laboratory efficiency and ensures accurate patient diagnoses. For more detailed information on EDTA tubes and their applications in medical diagnostics, please visit Sinymedical.

FAQs: Purple Cap Blood Collection Tubes

1. What are purple cap blood collection tubes used for?

Laboratories primarily use purple cap tubes for hematology tests, including Complete Blood Count (CBC), blood smears, and platelet counts. These tubes contain EDTA, which prevents blood clotting and preserves the shape and integrity of blood cells for analysis.

2. What is inside a purple cap blood collection tube?

The tubes contain EDTA (ethylenediaminetetraacetic acid), an anticoagulant that binds calcium to prevent clotting. EDTA also preserves blood cells, making it ideal for haematology tests.

3. Why are purple cap tubes not used for all blood tests?

Researchers specifically design purple cap tubes for tests that focus on blood cells and require whole blood, such as complete blood counts (CBCs) and blood smears. However, for tests like coagulation studies, which assess clotting, or chemistry panels, healthcare professionals need to use other tubes, such as those with blue or red caps that contain different additives.

4. How are purple cap tubes handled after collection?

After blood is collected in a purple cap tube:

• Gently invert the EDTA tube 8–10 times to mix the EDTA with the blood.
• Label the tube and store it at room temperature or as instructed.
• Perform testing within 24–48 hours for the best results.

5. Can purple cap tubes be used for DNA testing?

Yes, in some cases! Purple cap tubes with EDTA serve specific genetic and molecular tests because EDTA preserves DNA in blood samples, making them suitable for these analyses.

6. How long can blood in a purple cap tube be stored?

Blood samples in purple cap tubes remain stable at room temperature for 24–48 hours. However, labs may process specific tests within hours to ensure the highest accuracy.

You May Also Read

• A Complete Guide to EDTA Tubes: Types, Uses, and Benefits
• Top 5 Lab Tests That Require EDTA Tubes
• When should Blood Collection Tubes be Labeled
• Why EDTA is Used as the Additive in Purple Top Tubes?
• A Complete Guide to EDTA Tubes: Types, Uses, and Benefits

If you enjoyed this article, please subscribe to our YouTube channel. We provide product video tutorials. You can also follow us on Instagram and Facebook to stay up to date with new updates, news and special deals.