Difference Between Positive and Negative Blood

Main Difference – Positive vs Negative Blood

Positive and negative blood are the two types of blood classified by the RH blood group system. The RH blood group classifies blood based on the presence or absence of the antigen D on the surface of the red blood cells. The antigen D is also called ‘Rhesus factor’ (Rh factor). The main difference between Positive and negative blood is that positive blood consists of the Rh factor on the surface of the red blood cells whereas negative blood does not contain the Rh factor on the surface of the red blood cells. The two alleles that determine the RH blood group are the allele D and d. The allele D is the dominant allele and the allele d is the recessive allele. The genotypes, DD and Dd, produce the Rh factor on the surface of the red blood cells. The genotype dd is unable to produce the Rh factor on the surface of the red blood cell.

Key Areas Covered

1. What is Positive Blood
      – Definition, Determination, Transfusion
2. What is Negative Blood
      – Definition, Determination, Transfusion
3. What are the Similarities Between Positive and Negative Blood
      – Outline Of Common Features
4. What is the Difference Between Positive and Negative Blood
      – Comparison of Key Differences

Key Terms: Antigen D, Hemolytic Disease Of The Newborn (HDN), Hemolytic Transfusion Reactions (HTR), Negative Blood, Positive Blood, RH Blood Group, Rh Factor

What is Positive Blood

The term positive blood refers to the type of blood in which the red blood cells contains the Rh factor on the surface. The Rh factor is also called the Rh antigen. To date, 49 Rh antigens have been identified. The Rh antigen is a hybrid of Rh genes, RHD and RHCE. The numerous genetic rearrangements of those two genes produce different Rh antigens. Several significant Rh antigens include antigen D, C, E, c, and e. The most significant Rh antigen is antigen D. Therefore, the Rh factor is sometimes called the antigen D. The Rh blood group is shown in figure 1.

Difference Between Positive and Negative Blood

Figure 1: The RH blood group

What is Negative Blood

The term negative blood refers to the type of blood in which the red blood cells do not contain the Rh factor on the surface. However, the serum of the negative blood consists of anti-D antibodies due to the sensitization to the environment. If positive blood is transferred to a person with negative blood, hemolytic transfusion reactions (HTR) may occur, destroying the transfused blood. This may also cause the hemolytic disease of the newborn (HDN). Therefore, the Rh status should be determined during blood transfusions and in mothers-to-be. The symptoms of the HTR is shown in figure 2.

Main Difference - Positive vs Negative Blood

Figure 2: Symptoms of HTR

Similarities Between Positive and Negative Blood

The determination of both positive and negative blood is done by the RH blood group system
The determination of both positive and negative blood is essential prior to blood transfusion and in mothers-to be.

Definition

Positive Blood: Positive blood is the type of blood in which the red blood cells contain the Rh factor on the surface.

Negative Blood: Negative blood is the type of blood in which the red blood cells do not contain the Rh factor on the surface.

Percentage in the Population

Positive Blood: Positive blood can be found in 85% of the population.

Negative Blood: Negative blood can only be found in 15% of the population.

Genotypes

Positive Blood: Positive blood is determined by the DD and Dd genotypes.

Negative Blood: Negative blood is determined by the dd genotype.

Antigen D

Positive Blood: Antigen D is present on the surface of the red blood cells in the positive blood.

Negative Blood: Antigen D is absent on the surface of the red blood cells in the negative blood.

Anti-D Antibodies

Positive Blood: Anti-D antibodies are absent in the serum of the positive blood.

Negative Blood: Anti-D antibodies are present in the serum of the negative blood.

Blood Transfusion

Positive Blood: Positive blood can only be transferred to an individual with positive blood.

Negative Blood: Negative blood can only be transferred to an individual with negative blood.

Conclusion

Positive and negative blood are the two types of blood classified based on the Rh blood group. Positive blood comprise the Rh factor on the surface of the red blood cells. In contrast, negative blood lacks the Rh factor on the surface of the red blood cells. This is the main difference between positive and negative blood. But, anti-D antibodies are present in the negative blood serum. Therefore, positive blood cannot be transfused to negative blood. That means it is essential to determine the blood type prior to the blood transfusion.

Reference:

1. Dean, Laura. “The Rh blood group.” Blood Groups and Red Cell Antigens [Internet].U.S. National Library of Medicine, 01 Jan. 1970. Web. Available here. 14 Aug. 2017.

Image Courtesy:

1.”Main symptoms of acute hemolytic reaction” By Mikael Häggström, used with permission. – (Public Domain) via Commons Wikimedia