Acid Citrate Dextrose (ACD) tubes are specialized blood collection containers used when standard anticoagulants like EDTA or Heparin are insufficient for preserving the sample. These tubes contain a unique solution that prevents blood from clotting while also maintaining the health and metabolic needs of the blood’s cellular components. This dual function is particularly important for samples that require extended handling or storage before analysis. This combination makes ACD tubes necessary for a variety of complex laboratory and clinical procedures.
How the ACD Solution Preserves Blood
The Acid Citrate Dextrose solution is a carefully balanced mixture of three components, each with a specific function in preserving the blood sample. The primary anticoagulant is citrate, which stops the clotting cascade by binding to free calcium ions in the blood. Calcium is a cofactor required for many steps in the coagulation process, and its removal effectively prevents the blood from forming a clot.
The dextrose component, a simple sugar, acts as a nutrient source for red and white blood cells. This sugar provides the energy required for the cells to maintain their viability and structural integrity after being drawn from the body. Dextrose supports the energy-producing pathway that generates Adenosine Triphosphate (ATP), which is necessary for cellular function.
The third ingredient, citric acid, lowers the pH of the solution slightly, providing a more stable environment for the blood components. This mild acidity helps stabilize red blood cells and enhances the preservative effects of the other components. ACD tubes are available in two main formulations, ACD-A and ACD-B, which differ in component concentration; ACD-A generally has a higher concentration and stronger anticoagulant effect.
Use in Long-Term Blood Storage
Historically, a primary function of ACD was in blood banking, where its preservative qualities were essential for extending the viability of whole blood units. The inclusion of dextrose provided the necessary metabolic fuel to maintain red blood cell health during storage. This allowed blood to be stored for up to 21 days, a considerable increase at the time of its development.
ACD’s ability to preserve red blood cell integrity made it a foundation for modern transfusion medicine, enabling the safe storage and transport of blood. While newer preservative solutions like CPDA-1 (Citrate Phosphate Dextrose Adenine) have largely replaced ACD for routine mass storage of packed red blood cells, ACD remains a standard for specific blood component preparations. Its established track record makes it reliable for certain specialized blood collection and testing protocols within transfusion services.
Applications in Genetic and Cellular Testing
ACD tubes are indispensable in modern laboratory work that requires maintaining the health of living cells or the stability of genetic material. Because the ACD solution preserves white blood cell viability better than many other anticoagulants, it is the preferred choice for collecting samples for Human Leukocyte Antigen (HLA) typing. HLA typing is a procedure used to match donors and recipients for organ or bone marrow transplants, requiring live, healthy lymphocytes for accurate results.
ACD is highly suitable for molecular and genetic studies. When collecting blood for DNA or RNA analysis, especially for long-term biobanking or sequencing, ACD helps ensure the highest quality and yield of genetic material. This is because the white blood cells, the primary source of genomic DNA in blood, are kept intact and protected from degradation.
ACD tubes are routinely used in advanced cellular research, such as the isolation of peripheral blood mononuclear cells (PBMCs) for cell culture and immunology studies. Maintaining cell function and structure is paramount for experiments where viable, responsive cells are needed immediately after collection. For procedures like the preparation of Platelet-Rich Plasma (PRP), the ACD-A formulation is often preferred due to its superior capacity to preserve platelet morphology and function for therapeutic applications.