Blood Banking and Serology Reviewer for MTLE Philippines 2026

Blood Banking and Serology is one of the most technically demanding subjects in the Medical Technologist Licensure Examination. It combines immunohematology, blood group genetics, and transfusion medicine into a subject where precision is not optional. In a real blood bank, a single error can cost a patient their life. The MTLE reflects that gravity in how it tests this subject.

The good news is that blood banking follows logical systems. Once you understand the rules of ABO typing, Rh grouping, and compatibility testing, most questions become pattern recognition rather than pure memorization.

ABO Blood Group System

The ABO blood group system is the most important blood group system in transfusion medicine and one of the most heavily tested topics in MTLE blood banking.

ABO Genetics and Antigens

ABO blood group is determined by the ABO gene on chromosome 9. The three main alleles are IA, IB, and i.

Type A: Has A antigens on red blood cells. Has anti-B antibodies in plasma. Genotype IA IA or IA i.

Type B: Has B antigens on red blood cells. Has anti-A antibodies in plasma. Genotype IB IB or IB i.

Type AB: Has both A and B antigens on red blood cells. Has neither anti-A nor anti-B antibodies in plasma. Genotype IA IB. Universal recipient for red blood cells.

Type O: Has neither A nor B antigens on red blood cells. Has both anti-A and anti-B antibodies in plasma. Genotype ii. Universal donor for red blood cells.

ABO Typing Procedure

ABO typing requires both forward (cell) typing and reverse (serum) typing. Results must agree before a blood type is reported.

Forward (cell) typing: Patient red blood cells are tested against anti-A and anti-B reagents. Agglutination with anti-A means A antigen is present.

Reverse (serum) typing: Patient serum is tested against A1 cells and B cells. Agglutination with A1 cells means anti-A is present.

Discrepancies between forward and reverse typing must be resolved before issuing blood. Common causes: recent transfusion, bone marrow transplant, subgroup variants, cold autoantibodies.

Rh Blood Group System

The Rh system is the second most clinically important blood group system. The D antigen is the most immunogenic of all red blood cell antigens and the one that causes Hemolytic Disease of the Fetus and Newborn (HDFN).

Rh positive: D antigen present on red blood cells. About 85% of Filipinos are Rh positive.

Rh negative: D antigen absent. These individuals can develop anti-D if exposed to Rh positive blood.

Weak D (Du)

Weak D is a variant with reduced expression of the D antigen. Weak D patients are typed as Rh positive for transfusion purposes to prevent sensitization. Weak D donors are labeled as Rh positive.

Hemolytic Disease of the Fetus and Newborn (HDFN)

HDFN occurs when an Rh negative mother carries an Rh positive fetus. Maternal anti-D IgG antibodies cross the placenta and destroy fetal red blood cells.

Prevention: Rh immunoglobulin (RhoGAM) is given to Rh negative mothers at 28 weeks gestation and within 72 hours after delivery of an Rh positive infant. It prevents sensitization by destroying fetal cells before the mother's immune system can respond.

Compatibility Testing

Pre-transfusion Testing Steps

Type and Screen: ABO and Rh typing plus antibody screen. Done before any potential transfusion.

Type and Crossmatch: Done when blood is actually needed for transfusion.

The Crossmatch

Major crossmatch: Patient serum tested against donor red blood cells. Detects antibodies in patient that could destroy donor cells. This is the critical compatibility test.

Minor crossmatch: Donor serum tested against patient red blood cells. Less clinically significant in modern practice.

Electronic crossmatch: Computer-based compatibility check allowed when patient has no clinically significant antibodies and has had two separate ABO typings on record.

Antibody Identification

When an antibody screen is positive, the antibody must be identified using a panel of red blood cells with known antigen profiles. The pattern of reactions across the panel identifies the specificity of the antibody.

Blood Components and Their Uses

Transfusion Reactions

Transfusion reactions are a consistent source of MTLE questions because they require integrating clinical presentation with laboratory findings.

Acute Hemolytic Transfusion Reaction (AHTR): Most dangerous transfusion reaction. Caused by ABO incompatibility usually due to clerical error. Signs: fever, chills, back and flank pain, hemoglobinuria (red-brown urine), hypotension, shock. Management: stop transfusion immediately, maintain IV access, notify blood bank, send post-reaction samples.

Febrile Non-Hemolytic Transfusion Reaction (FNHTR): Most common transfusion reaction. Caused by recipient antibodies against donor leukocyte antigens. Temperature rise of 1°C or more during or within 4 hours of transfusion. Management: slow or stop transfusion, administer antipyretics. Prevented by using leukoreduced blood products.

Allergic Reaction: Caused by recipient antibodies against donor plasma proteins. Ranges from mild urticaria (hives) to anaphylaxis. Mild reactions: slow transfusion, give antihistamines. Anaphylaxis: stop transfusion, give epinephrine.

Transfusion Associated Circulatory Overload (TACO): Volume overload from transfusion. Signs: dyspnea, hypertension, pulmonary edema. Most common in elderly patients and those with cardiac disease.

Transfusion Related Acute Lung Injury (TRALI): Non-cardiogenic pulmonary edema within 6 hours of transfusion. Caused by donor antibodies against recipient neutrophil antigens. Characterized by hypoxia and bilateral pulmonary infiltrates without evidence of cardiac overload.

Basic Serology: Antigen-Antibody Reactions

Serology tests detect antigens or antibodies using known reagents. The principles underlying these reactions appear throughout the MTLE.

Direct Antiglobulin Test (DAT) / Direct Coombs Test: Detects antibodies or complement already bound to the patient's red blood cells in vivo. Positive in autoimmune hemolytic anemia, HDFN, and transfusion reactions.

Indirect Antiglobulin Test (IAT) / Indirect Coombs Test: Detects antibodies in patient serum that could bind to red blood cells in vitro. Used in antibody screening, crossmatching, and Rh typing for weak D.

Key distinction: DAT looks at what is on the cells. IAT looks at what is in the serum.

Practice What You Just Learned

Blood banking questions in the MTLE cover ABO and Rh typing, crossmatching, blood component selection, and transfusion reaction recognition. Practice all of these at LisensyaPrep. No account needed.

Practice MTLE Blood Banking Questions at LisensyaPrep

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