Decoding the SID System: Understanding, Diagnosing, and Genetic Testing for Blood Group Disorders

Expert Reviewed By: ⁠Dr. Brandon Colby MD

The blood group system is a classification of blood types based on the presence or absence of specific antigens on the surface of red blood cells. These antigens are inherited and can determine compatibility in blood transfusions, organ transplantation, and other medical procedures. The SID blood group system is a relatively new and lesser-known system that has significant implications for understanding, diagnosing, and using genetic testing for blood group disorders.

The SID Blood Group System and Its Association with the Sda Antigen

The SID blood group system is characterized by the presence or absence of the Sda antigen on the surface of red blood cells. The Sda antigen is a carbohydrate structure that is attached to various glycoproteins and glycolipids on the cell surface. The SID blood group system was first identified in 2018 and has since been the subject of ongoing research to better understand its implications for blood group disorders and transfusion medicine [1].

Molecular Genetic Mechanisms behind the P1 and Sda Antigens

Research has shown that the presence or absence of the Sda antigen is determined by the activity of a specific enzyme called β-1,4-N-acetylgalactosaminyltransferase (B4GALNT2) [2]. This enzyme is responsible for the addition of N-acetylgalactosamine (GalNAc) to the glycan structures found on the surface of red blood cells. The P1 antigen, another carbohydrate blood group antigen, is also associated with the B4GALNT2 gene. The molecular genetic mechanisms behind the P1 and Sda antigens are complex and involve the regulation of B4GALNT2 gene expression, as well as the specific glycan structures that are modified by the enzyme [2].

Genetic Testing for the SID Blood Group System

Genetic testing for the SID blood group system can help identify individuals who may be at risk for blood group incompatibilities and related complications. Molecular genetic techniques, such as polymerase chain reaction (PCR) and DNA sequencing, can be used to analyze the B4GALNT2 gene and identify the presence or absence of the Sda antigen [3].

Uses of Genetic Testing for Blood Group Disorders

Genetic testing for blood group disorders, including the SID system, can provide valuable information for various medical applications:

• Transfusion Medicine: Identifying the presence or absence of specific antigens, such as the Sda antigen, can help determine compatibility in blood transfusions and reduce the risk of transfusion reactions [1].
• Organ Transplantation: Blood group compatibility is crucial for the success of organ transplantation, and genetic testing can help identify potential donors and recipients with compatible blood group antigens [4].
• Prenatal Diagnosis: Genetic testing can be used to identify blood group incompatibilities between a mother and her unborn child, which may cause hemolytic disease of the fetus and newborn (HDFN) [3].
• Population Genetics: Studying the distribution and prevalence of blood group antigens, such as the Sda antigen, can provide insights into the genetic diversity and evolutionary history of human populations [4].

In conclusion, the SID blood group system is an important area of research that can enhance our understanding of blood group disorders and improve patient outcomes in transfusion medicine, organ transplantation, and prenatal diagnosis. Genetic testing for the SID system and other blood group antigens can provide valuable information for various medical applications and contribute to a better understanding of human genetic diversity.

About The Expert Reviewer

Dr. Brandon Colby MD is a US physician specializing in the personalized prevention of disease through the use of genomic technologies. He’s an expert in genetic testing, genetic analysis, and precision medicine. Dr. Colby is also the Founder of  and the author of ⁠⁠Outsmart Your Genes.

Dr. Colby holds an MD from the Mount Sinai School of Medicine, an MBA from Stanford University’s Graduate School of Business, and a degree in Genetics with Honors from the University of Michigan. He is an Affiliate Specialist of the American College of Medical Genetics and Genomics (⁠⁠ACMG), an Associate of the American College of Preventive Medicine (⁠⁠ACPM), and a member of the National Society of Genetic Counselors (⁠NSGC)