Basic rules of clinical transfusiology
According to modern medical standards, a recipient is permitted to be transfused exclusively with same-group (by the AB0 system) and same-Rh-factor blood.
However, in clinical practice, there are emergency situations where strict exceptions are permitted:
- The Ottenberg rule may be applied, which implies transfusing blood from a universal donor.
- Rh-positive blood transfusion to an Rh-negative patient is permitted, but in a volume not exceeding 500 mL.
- Extremely important: in pediatric practice, any exceptions to transfusiology rules are strictly unacceptable. Children are transfused only with strictly identical blood.
Separate regulations apply to blood plasma. Thus, plasma of groups A(II) and B(III) is permitted to be transfused to patients with blood group 0(I). If the recipient has the first group 0(I), they can also be transfused with plasma of the identical 0(I) group.
Requirements for standard sera
To perform the test, it is necessary to prepare two sets of sera of the first three groups — I(0), II(A), and III(B), and they must strictly belong to different batches. You will also need one ampoule of IV(AB) serum, a vial of isotonic sodium chloride solution, individual pipettes for each ampoule, a porcelain plate, glass slides, lancets, cotton wool, and alcohol.
Before starting the procedure, the physician must assess the suitability of the reagents. They should be stored in a refrigerator at a temperature of 4–10 °C.
Criteria for serum suitability:
- Presence of label-passport: it must clearly indicate the group, batch, titer, expiration date, and place of manufacture. The use of ampoules without a label is strictly prohibited.
- Appearance: the liquid must be light and completely transparent. If turbidity, flakes, sediment, or an expired shelf life is observed, the reagent is rejected.
- Activity: the minimum acceptable titer is 1:32. At the same time, the initial signs of erythrocyte clumping must appear no later than 30 seconds after mixing.
Color marking of ampoules:
- I (0) — liquid is colorless, no marking stripes.
- II (A) — liquid is blue, 2 blue stripes are applied to the label.
- III (B) — liquid is red, 3 red stripes on the label.
- IV (AB) — liquid is yellow, 4 yellow stripes on the label.
Step-by-step procedure
The reaction is performed under good lighting, following a strict sequence of actions:
- Marking: a standard white plate is divided with a colored pencil into four sectors. They are labeled clockwise: I(0), II(A), III(B).
- Applying reagents: large drops of sera are placed in the marked squares (obligatorily from two different batches for each of the three groups).
- Blood sampling: the patient's fingertip is treated with alcohol and punctured with a special lancet. The first drop of blood that appears must be wiped away with a cotton ball.
- Mixing: the blood is sequentially transferred into the drops of serum, using different corners of a clean glass slide for each sample. The drop of blood must be significantly smaller than the drop of serum (5–10 times). The substances are thoroughly mixed.
- Observation: the plate is periodically rocked. After 3 minutes, a preliminary evaluation is performed. Then, a drop of isotonic NaCl solution is added to each drop where a reaction has occurred, and the plate is rocked again. The final result is recorded in exactly 5 minutes.
Evaluation and interpretation of results
During observation, the physician records the presence or absence of the agglutination reaction.
- Positive reaction: small granules and flakes of clumped erythrocytes form in the drop, which do not disintegrate after the addition of isotonic NaCl solution.
- Negative reaction: the drop remains completely transparent, maintains a uniform pink color, with no flakes or granularity appearing.
Decoding combinations:
- Group I (0): agglutination is completely absent in all drops (with sera of groups I, II, and III of both batches).
- Group II (A): reaction is negative in the drop with II(A) serum, but positive with reagents I(0) and III(B).
- Group III (B): reaction is negative in the drop with III(B) serum, but positive with sera I(0) and II(A).
- Group IV (AB): reaction is positive with all three sera.
Important clarification for the IV(AB) group: to rule out error, it is necessary to perform an additional control reaction with standard IV(AB) serum. Only if agglutination is absent in this control drop is the diagnosis of the IV(AB) group considered finally confirmed. Any combination not described above indicates a technical error during the study.
Briefly: answers to topical questions
What are the compatibility rules for blood plasma transfusion?
Compatibility rules for blood plasma transfusion require mandatory consideration of the AB0 group affiliation of the donor and recipient, as well as performing a biological test. The following rules apply to specific groups:
- Plasma of groups A(II) and B(III) — can be transfused to 0(I) group recipients.
- Plasma 0(I) — transfused to recipients of the same group only.
What types of false agglutination exist in blood group determination?
When determining the blood group, two main types of false agglutination are distinguished, in which true clumping is absent, but the appearance of a reaction is present. These include:
- Pseudoagglutination — occurs due to drying of the drop and the formation of erythrocyte "rouleaux".
- Cold agglutination — develops when the test is performed at ambient temperatures below 15 °C.
To prevent a false-positive result, an isotonic sodium chloride solution is added to the drop and the study is conducted at a temperature above 15 °C.
What agglutinogens and agglutinins are characteristic of each of the four blood groups according to the AB0 system?
Each of the four blood groups according to the AB0 system is characterized by a strictly defined ratio of agglutinogens (in erythrocytes) and agglutinins (in serum). Normally, only non-matching components are present in the blood.
| Blood group | Erythrocyte agglutinogens | Serum agglutinins |
|---|---|---|
| I (0) | none | α and β |
| II (A) | A | β |
| III (B) | C | α |
| IV (AB) | A and B | none |
Varieties of agglutinogen A (A1 and A2) are also known, which form the corresponding subgroups.
To easily remember the labeling of sera, look at the number of colored stripes on the label: it always matches the blood group number. The first group has zero stripes (colorless), the second has two stripes (blue), the third has three (red), and the fourth has four (yellow).
Class and exam questions
For what purpose is isotonic NaCl solution added to the reaction mixture?
The solution is added three minutes after the start of the reaction to differentiate true agglutination from false. If the formed flakes do not disperse upon the addition of NaCl, the reaction is truly positive.
What does it mean if agglutination occurred in all drops, including the IV(AB) serum?
Normally, IV(AB) serum should not produce a positive reaction. If erythrocyte agglutination occurs absolutely everywhere, it indicates panagglutination or a technical error — the result is invalid.
Where are blood typing results recorded?
The information must be recorded in the medical history and entered on its title page. The entry must be certified by the personal signature of the physician who performed the test, along with the current date.
What else to study on this topic
- Mechanism of the hemagglutination reaction: interaction of antigens and antibodies
- Errors in blood typing: false panagglutination
- Ottenberg's rule and extreme situations in transfusiology
- Plasma transfusion rules: AB0 system compatibility
- Express method for Rh factor determination
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