Low levels of hemoglobin can result from acute or chronic blood loss, excessive red cell breakdown or failure to produce sufficient levels of red cells resulting in anemia. Anemia occurs in 42% of global pregnancies as the mother's body is unable to produce red blood cells in proportion to the 50% increase in blood volume associated with pregnancy. Acute blood loss most often occurs postpartum due to uterine relaxation. Low concentrations of red blood cells makes it difficult for the body to oxygenate itself and the fetus.
Blood transfusion is often used to correct this, however, the transfused blood cells must be compatible with the recipients blood. Incmopatible blood results in a dangerous immune response to the foreign transfusion. If incompatible blood is transfused, the patient may suffer from hemolysis, renal failure and possibly death.
Mechanism of Action
Blood group tests use the principle of agglutination to differentiate between blood types. To trigger agglutination, whole blood samples are mixed with three test reagents: antibodies matching the A, B, and Rh surface antigens. Samples with antibody-antigen pairs clump together. This visible agglutination signals the presence of the antigen in the blood. Agglutination can be performed on an open surface, test tube, or micro-array for high throughput.
Current use in High-Resource Settings
Blood typing is typically done in a centralized laboratory setting wherein high throughput instruments such as the Immucor Galileo which can load 224 samples at a time for blood type as well as limited infectious disease screening. Blood banks can typically run 30,000 samples a year with one such machine.
Application in Low-Resource Settings
Blood banking does not adequately cover the population requiring transfusion in many low-resource settings, and patients requiring a transfusion will sometimes ask compatible donors from their friends and family to accompany them for direct donation. These donors may submit to rapid, card-based confirmatory testing immediately (like the Eldoncard above) before transfusion. Determining blood type, however, is only a first step. Especially in areas with high prevalence of HIV, infectious disease screening is an important part of transfusion safety.