A case of red blood cell condensation leading to deviation of routine blood count

Preface

Cold agglutinin is an IgM antibody directed against the surface of red blood cell membranes.
It causes red blood cell self-coagulation in vitro and under low temperature conditions.
It is one of the important factors that interfere with routine blood analysis.
It mainly affects red blood cells and their parameters
.

Case history

A 64-year-old male patient was admitted to the hospital with "anemia".
The blood test results are as follows (see Figure 1): RBC 0.
17×1012/L, Hb 116g/L, HCT 1.
8%, MCV 105.
9fl, MCH 682.
4pg, MCHC is as high as 6444g/L, red blood cell related alarm information: red blood cell agglutination? , So the staff observed the appearance of the specimen: it was agglomerated in granular form (Figure 2)
.

Red blood cells are not proportional to hemoglobin, and MCH and MCHC are extremely high.
Combined with clinical cases, the staff guessed that it is most likely that the abnormal test results are caused by condensation
.

Figure 1 Unprocessed original specimen inspection page

Figure 2 Appearance of untreated specimen

Treatment measures: Place the specimen in a 37°C incubator and warm it for 30 minutes.
The appearance of the specimen: the granular agglomeration disappeared (Figure 3).
The test results are as follows (Figure 4): RBC 1.
94×1012/L, Hb 67g/L , HCT 20.
9%, MCV 107.
7fl, MCH 34.
5pg, MCHC 321g/L, at this time the red blood cell aggregation abnormal alarm message disappears, indicating that the red blood cell aggregation is reversible, and the aggregation phenomenon disappears after the temperature is restored
.

Figure 3 Appearance of the specimen after 30min in 37℃ water bath

Figure 4 Specimen detection page after 30min in 37℃ water bath

case analysis

The mechanism of cold agglutination phenomenon is currently unclear.
It is common in cold agglutinin syndrome, hematological diseases, tumors, autoimmune diseases, Mycoplasma pneumoniae infection, etc.
[2].
This antibody also exists in some healthy people, usually with titer.
It is relatively low and generally does not cause agglutination
.

In this case, the accumulation of red blood cells caused by cold agglutinin, which affects the results of the blood cell analyzer to varying degrees
.

The channel setting of white blood cells and platelets using fluorescence flow cytometry combined with multiple reagents is different from that of red blood cells, so red blood cell agglutination has little effect on white blood cells and platelets
.

1.
Plasma exchange method: suitable for heavily agglutinated specimens.
Centrifuge the routine blood specimens at low speed for 3-5 minutes.
Use a pipette to slowly remove and discard the upper plasma.
Record the discarded amount, and then add the same amount of 37°C normal saline.
, After mixing, centrifuge and lift the upper liquid again, repeat the above steps 3 times, and then measure on the machine
.

2.
Pre-dilution mode detection: suitable for severe agglutination, the instrument will provide the sample volume requirements for pre-dilution mode, draw blood samples and diluents as required, and quickly test on the machine after a 37 ℃ water bath (better practice is to pre-warm both , And then mix and incubate)
.

3.
Manual counting: Add 10uL of 37℃ warm bath blood to 2.
0mL of 37℃ warm saline, mix well, and drop it on the counting plate for counting
.

Summarize

The most common season for cold syndrome is winter, and its existence often troubles the test items.
The most common is the influence on blood routine and blood typing
.