# An Efficient System for Automatic Blood Type Determination Based on Image Matching Techniques
## 2 Blood Typing: Overview, Problem, and Challenges  
### Overview  
Blood typing or blood grouping is the process of determining the type or the group of the human blood depending on the presence or absence of certain antigens on the surface of the red blood cells. This process is important for blood transfusion, as not all blood types are compatible with one another. Receiving an incompatible blood type motivates the human body to generate antibodies against the new blood, which causes clotting in the blood vessels and may threaten life.  
Two blood group systems are used to identify the blood type: (1) ABO and (2) Rh systems. According to the first system, the blood is classified depending on the presence of A and B antigens into one of the following groups or types: A, B, AB, or O. In types A and B, the surface of the red blood cells contains A and B antigens, respectively. In type AB, the surface contains both A and B antigens, whereas it contains neither of them in type O. The Rh system is the second most significant blood group system, where it classifies the blood into positive (+) or negative (-) according to the presence and the absence of the Rh antigens, respectively. Both ABO and Rh grouping systems yield into eight possible human blood types; A+, A-, B+, B-, AB+, AB-, O+, and O- [22]. Table 1 summarizes these types and the accepted donor's blood type during blood transfusion to avoid blood clotting.  
The blood typing process is performed by mixing three spots of the same blood sample with A, B, and D antibodies, respectively, and then observing the agglutination of the three spots. The blood is classified into ABO groups as follows:  
* **Blood type A**: Agglutination of the spot mixed with A antibodies.
* **Blood type B**: Agglutination of the spot mixed with B antibodies.
* **Blood type A**: Agglutination of the spots mixed with A and B antibodies.
* **Blood type O**: No agglutination of the spots mixed with A and B antibodies.  
The Rh type is determined according to the agglutination of the spot mixed with the D antibodies. If it is agglutinated, the blood type is positive; otherwise, it is negative. Figure 2 illustrates this process, where the antibodies A, B, and D were mixed with each blood spot from left to right in each image, respectively.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Blood Type** & \begin{tabular}{c} **Presence of A-Antigen** \\ **in the Red Blood Cells** \\ \end{tabular} & \begin{tabular}{c} **Presence of B-Antigen** \\ **in the Red Blood Cells** \\ \end{tabular} & \
\begin{tabular}{c} **Presence of Rh-Antigen** \\ **in the Red Blood Cells** \\ \end{tabular} &
\begin{tabular}{c} **Donor’s Compatible** \\ **Blood Types** \\ \end{tabular} \\ \hline A+ & YES & NO & YES & A+, A–, O+, O– \\ \hline A\(-\) & YES & NO & NO & A–, O– \\ \hline B+ & NO & YES & YES & B+, B–, O+, O– \\ \hline B\(-\) & NO & YES & NO & B–, O– \\ \hline AB+ & YES & YES & YES & Everyone \\ \hline AB– & YES & YES & NO & AB–, A–, B–, O– \\ \hline O+ & NO & NO & YES & O+, O– \\ \hline O– & NO & NO & NO & O– \\ \hline \hline \end{tabular}
\end{table}
Table 1: Blood types and its compatibility with each other.  
Figure 2: _Cont._