Keep warm together? Blood routine test found "jelly blood", it turns out that red blood cells are also "afraid of cold"

After the Spring Festival, the cold wind blew in Changsha, and the body felt very cold. In this cold weather, the laboratory department may receive some unexpected "little gifts".

Just recently, the laboratory department of Changsha Taihe Hospital received a "special" blood sample. Although it was sent for inspection according to normal procedures, the blood had coagulated into "jelly", the red blood cell parameters of the routine blood test could not be measured, the positive and negative blood typing did not match, the red blood cell antibody screening was positive, and the cross-matching was incompatible... The results confirmed that the specimen had undergone " cold agglutination " phenomenon.

Blood specimen: visible clots

So, why does the anticoagulated blood sample show the phenomenon of "cold agglutination"? What should we do if we encounter "cold agglutination" in the routine blood sample? Today, Pi Lexiang, director of the laboratory department of Changsha Taihe Hospital, will talk to you about this related topic.

1. What is "condensation"?

"Cold agglutination" is a common phenomenon in clinical laboratory work, which is caused by cold agglutinins . After blood collection, red blood cells aggregate in a test tube in a low-temperature environment , especially in winter and spring when the temperature is low. In severe cases, red blood cells may aggregate on the wall of the anticoagulated blood test tube (EDTA anticoagulation tube) to form a fine sand-like state.

"Cold agglutination" is a reversible red blood cell agglutination phenomenon and is not caused by improper blood collection.

2. Why does the phenomenon of "condensation" occur?

Cold agglutinin is an antibody against red blood cell membrane antigens, mainly IgM antibodies, with a small number of IgG and IgA types. It has a relatively low titer in healthy humans and generally does not cause cold agglutination of red blood cells.

However, when the ambient temperature drops (below 32°C, especially 0-4°C) or in patients with Mycoplasma pneumoniae, influenza virus infection and other malignant tumors, solid tumors, autoimmune diseases, etc. , cold agglutinins may act on their own red blood cell antigens and cause reversible red blood cell "cold agglutination" phenomenon. When the temperature rises to 37°C, the agglutination disappears.

Does it sound amazing? However, the phenomenon of blood "cold agglutination" will not only lead to deviations in the results of red blood cell related parameters (such as RBC, HCT, MCV, MCH, etc.) , but also interfere with the results of blood type serum blood tests (blood type, antibody screening, cross-matching, etc.), which will mislead clinicians. Therefore, it is very important to detect and deal with "cold agglutination" specimens as early as possible.

3. How to solve the problem of cold agglomeration?

1. Incubation method:

Place the specimen in a 37°C incubator for 30 minutes to one hour, and immediately test it on the machine. This method is simple to operate and commonly used in clinical practice. The disadvantage of this method is that it takes a relatively long time, and for strongly agglutinated specimens, the correction effect may not be ideal.

2. Plasma exchange:

The blood routine specimen is centrifuged at 3000r/min for 5min, the upper plasma is aspirated, and the instrument diluent (liquid used to dilute samples or reagents) or saline preheated at 37℃ is added and mixed thoroughly. After repeated replacement 3 times, the test is performed on the machine. Because some white blood cells and platelets are easily aspirated during the replacement process, the white blood cells and platelets will be reduced to varying degrees. For white blood cells and platelets, it is necessary to refer to the first result for reporting. The disadvantage of this method is that the operation is more complicated and time-consuming, so it can be used as an alternative.

3. Pre-dilution method:

The instrument diluent is added to a microcentrifuge tube (EP tube), and then placed in a 37°C water bath for incubation for 30 minutes. The incubated diluent is then mixed with untreated peripheral blood and tested on the instrument. This method is simple to operate and is also very effective for blood specimens with high cold agglutinin titers, significantly superior to direct incubation and plasma exchange methods.

4. Machine-side detection method:

The patient resamples and immediately tests on the machine, completing the test at the beginning of the "cold agglutination". The disadvantage is that blood needs to be drawn again, which is not very suitable for clinical patients.

4. What is the clinical significance of cold agglutination phenomenon?

In addition to some physiological "cold agglutination" phenomena, such as low temperature; "cold agglutination" phenomenon may also occur in certain disease states, such as mycoplasma infection, autoimmune hemolytic anemia, infectious mononucleosis, severe anemia, multiple myeloma, mumps, etc. These diseases can increase the titer of cold agglutinins, thereby leading to the occurrence of "cold agglutination" phenomenon.

Cold agglutination can not only help diagnose some diseases, but also indicate potential health problems in some cases, such as cold agglutination hemolysis. As mentioned earlier, cold agglutination reactions may cause red blood cell destruction, which is clinically manifested as hemolytic anemia. Patients may experience symptoms such as fatigue and jaundice, and the number of red blood cells in the blood decreases.

Director Pi Lexiang said:

Cold agglutination is a relatively special phenomenon in medical testing, which usually occurs at lower temperatures. Therefore, in clinical experiments, if the temperature is too low, it may also affect the experimental results and cause false positives or false negatives.

It not only plays an important role in the diagnosis of some diseases, but also provides valuable diagnostic and treatment information for clinicians. I hope that through the introduction of this article, everyone will have a more comprehensive understanding of cold agglutination, and we can better apply this phenomenon to provide patients with more accurate diagnosis and treatment plans.

Hunan Medical Chat Special Author: Li Xiaoyang, Department of Laboratory, Changsha Taihe Hospital

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(Edited by Wx)