Author: Zhang Fuyong
Case 1
EDTA-dependent platelet aggregation (points to watch): patient, respiratory medicine, male, fever to be investigated, blood routine today, PLT 9×109/L, see the instrument to show platelet aggregation. Contact clinical findings that the patient did not have a tendency to bleed, the patient had several blood routine PLT checks outside the hospital were reduced, and platelet transfusion was ineffective. In this case, it is suspected that the pseudothrombocytopenia caused by EDTA-dependent platelet aggregation was suspected, so the clinical replacement of sodium citrate (PT tube) was prompted for review, and PLT 185×109/L was obtained. The main point of watching the film is to focus on the end of the film, and it can be seen that there are platelets between the gaps in the blood plate.
Case 2
Condensation (treatment of severe water baths that are difficult to correct, how to judge that it has been corrected): Patient, department? diagnosis?
RBC：1.76×1012/L；
HGB：109.8g/L；
HCT：0.159；
MCV 125fl。
Retest after water bath:
RBC：3.621×1012/L
HGB：112.5g/L
HCT：0.34
MCV：105fl。
However, if you encounter a serious case, the water bath for more than half an hour is ineffective, how to deal with it?
Case 3
Cold disease (different from condensation): suffering from so-and-so, male, 27 years old, hematology, leukemia? The patient is initially diagnosed in the emergency department, and the blood is immediately sent for testing and immediately on the machine to send the results:
WBC：1.46×109/L；
PLT:330.6×109/L。
Re-examination after admission the next day:
WBC：335.20×109/L；
PLT:1107×109/L。
The push tablets found that both white blood cells and platelets are rare and should be reduced. Considering that the initial diagnosis is an emergency examination and the temperature of the specimen is acceptable, the specimen is immediately put on the machine after 30 minutes of water bath, and the results are:
WBC：1.79×109/L；
PLT:10.2×109/L。
This result is more reliable. How is this case explained?
Case 4
HCT is inconsistent with HGB (how to explain it clinically): patient, male, hematology, chronic myeloid leukemia blood routine:
WBC：423.5×109/L；
RBC：1.9×1012/L；
HGB：49g/L；
HCT：0.31；
MCV：159fl。
Clinical call, question why is HGB inconsistent with HCT, hemoglobin is so low, and the hematocrit is only slightly lower? To explain this problem, it is necessary to understand which of these indicators are measured and which are converted.
Written in the front: Please look at the following with a critical eye with a skeptical spirit, in view of the limited level, if there is any inappropriateness in the statement, please consult the relevant literature and treatises by yourself. The main thing mentioned in the article is error analysis, that is, the false increase or decrease, in actual work, we should pay attention to the clinical characteristics of the patient, strengthen communication with clinicians, and strive to issue an accurate report.
Let's start with the indicators of a blood test list and talk about the influencing factors between the indicators. The counting of WBC, RBC, PLT is based on the Kurt principle, the cell through the counting cell due to the presence of resistance and voltage, the voltage level is the size of the pulse, reflecting the size of the cell, the number of pulses reflects the number of cells.
(1) What happens in the WBC channel?
Before performing a blood cell assay, whole blood specimens must be diluted in a certain proportion with a dilution on the outside or inside of the instrument, generally measuring white blood cells with a dilution multiple of 1:251. In the leukocyte channel, in order to make the red blood cells all rupture, a certain amount of hemolytic agent (lyse) is added to rupture the red blood cell membrane, releasing hemoglobin, leaving only a tiny remnant of the red blood cell membrane. The pulses produced by volume > 35fl particles are classified as white blood cell counts. At this time, there are white blood cells and platelets in this channel, which can be distinguished because the platelet volume is much smaller than that of white blood cells. Therefore, red blood cells and platelets can affect WBCs in some cases.
For example, in patients with severe anemia, the bone marrow hematopoietic system is active, and some immature red blood cells are released into the peripheral blood, that is, there is nuclear red, and there is still a nucleus after the destruction of the hemolytic agent, so that the WBC is high, and it should be corrected strictly speaking. If 100 WBCs are microscopic and 10 are nucleated red, the WBC correction value should be (100/110) × WBC count value.
Another example is the resistance of red blood cells to hemolytic agents, which is seen in patients with impaired liver function (cirrhosis, liver cancer, etc.) and abnormal hemoglobinopathy (ground poverty, etc.).
Platelet aggregation, large platelets. We know that red blood cell debris can affect PLT, making it pseudo-elevated, so in turn platelet aggregation, does giant platelet also affect RBC? In fact, it is mainly affecting WBC, and the reasons will be explained later.
The precipitation of cold proteins, the reasons for the pseudo-increase of WBC in Example 3, are also described later.
The preceding factors are the influencing factors that increase the WBC, and there are also factors with pseudo-decrease, such as white blood cell aggregation, which can occur in cold agglutination and anticoagulant-related aggregation. Rarely seen, we have not yet encountered in our work, or neglected due to limited levels.
(2) In the RBC channel, what happens?
In this channel, there is no special treatment for white blood cells and platelets, so there are both, so why is there still a countable RBC? First of all, leukocytes, looking at their units and red blood cells can find a difference of 1000 times, due to the difference in coefficients, so in fact WBC: RBC is roughly 1: 750, so the influencing factors of WBC are two or three digits after the RBC decimal point, so under normal circumstances, it is naturally negligible. The second is platelets, as mentioned above, through Kurt's principle of electrical impedance, red blood cells are distinguished from platelets according to the size of the pulse, so that the PLT count results can be obtained.
Here's what's the influence:
Some leukemias have extremely high WBCs, such as more than 400,000 in case 4, at this time WBC has an impact on RBCs, it is precisely for this reason that the blood routine characteristics of case 4 appear, which are described in detail later.
When platelet aggregation occurs, why did the platelets at this time mainly affect WBC, not RBC. The reason is the same as the normal WBC interference with RBCs is negligible. The unit of PLT is also 1000 times different from the order of RBC, although the coefficient of normal PLT reaches 100 to 300, but the value of PLT decreases significantly when aggregation occurs, as in Example 1, it can be as low as single digits, so just as the interference of WBC can be ignored when counting RBCs, the effect of aggregated platelets on RBCs can also be ignored. Instead, in the WBC channel, when the volume of platelets that accumulate is large enough, it affects WBC and raises it.
The influencing factors of RBC pseudo-reduction generally have cold agglutination, such as Example 2, red blood cell aggregation caused by anticoagulants, and red blood cell aggregation caused by autoimmune diseases, which have not been encountered.
(3) PLT is also in the RBC channel, as mentioned earlier, the impact of PLT on RBC, and now the error situation caused by the interference of PLT affected factors.
Pseudo-elevation, red blood cell debris (lysis, DIC, etc.), microcytic cells, cold protein precipitation (e.g., Example 3).
False reduction. It should be emphasized that special attention should be paid to the reduction of PLT, especially for first-time patients. As described in Example 1, PLT reduction can mislead clinical platelet transfusion (risk of transfusion), bone puncture (patient guilt), and if an accident occurs, the consequences are immeasurable. The Ministry of Health issued the "Technical Specifications for Clinical Blood Transfusion" and stated that PLT9/L should already consider platelet transfusion. "Therefore, according to experience, outpatient PLT is less than 50×109/L, and there is no bleeding, the credibility is not high." (From "EDTA-dependent platelet aggregation" "Laboratory and Clinical Communication - Case Study 200 Cases" P145) Therefore, when the initial PLT is reduced, it is recommended that it is less than 100, and smear re-examination should be considered.
PLT reduction, can be seen in the blood draw is not smooth occurrence of invisible agglutination with the naked eye, and even some nurses who lack basic understanding of the blood draw blood to find the clot directly pick out the clot for testing, this ignorance is outrageous; followed by the EDTA-dependent platelet aggregation mentioned in Example 1, the principle of this situation seems to remain to be explored, the probability of occurrence in outpatients is about one in a thousand, and this situation should be highly valued in terms of the outpatient volume of our hospital.
If this is the case, you can refer to the following information:
1, is the histogram, it can be seen that the leftmost WBC histogram is elevated at about 50fl, which is the aggregateD PLT count is WBC;
2. It is an alarm message, which can report giant platelets (Giant Platelets) and platelet clots (Platelet Clumps);
3. It is to contact the clinic to understand that the patient should have no bleeding tendencies such as skin purpura and mucosal bleeding;
4. It is necessary to push the re-examination of the tablet, and should pay close attention to the crevices of the red blood cells at the end of the film, and a large number of platelet aggregation can be found.
At this time, we should contact the clinic to inform our suspicions, and after the replacement of the PT tube is verified, the doctor should inform the patient to use the PT tube in the future blood routine, so that it can be considered in place.
In summary, after saying these three big heads, by the way, when pushing the lens, it is often necessary to determine whether the platelets, white blood cell number and detection values are roughly the same, which is recorded in the book "Peripheral Blood Cell Morphology Examination Technology" (Wang Xiaoxia, People's Medical Publishing House) as follows:
With regard to inferring the number of platelets by blood tablets, when the distribution is even, there is no abnormal aggregation or fibrin filaments, the smear can roughly estimate the number of platelets by the method of the number of platelets (× 109/L) = the average number of platelets in a field of view of oil microscopy× 15×109/L.
The estimation method of WBC is also uniformly distributed, with a white blood cell count (×109/L) = the average number of white blood cells in a high-magnification field of view×2×109/L.
There are also literature and monographs on the method of documentation:
Number of platelets in the blood smear (×109/L) = number of platelets when counting 100 white blood cells/100 white blood cells× white blood cells (×109/L). Note: The number of white blood cells is the counting result of the blood analyzer.
Phase contrast microscopy method: take 20 μL of whole blood plus 10 g/L ammonium oxalate dilution 0.38 mL of hemolysis for 10 min, fill into the bovine and abalone counting plate wet box for 30 min, high magnification mirror counting around the central square around 4 squares and 1 central square; when platelets are particularly small, count the central square 1 large grid.
——The role of blood smear platelet counting on blood analyzer[J]. Journal of Clinical Laboratory Research,2004,2(6):442,462.
（4）HGB
Because its detection principle is colorimetry, through the change of absorbance, therefore, jaundice, lipid blood, hyperglobulin, high white blood cells, high platelets may affect the HGB results, but whether there are statistical differences in their effects is unknown. In the case of jaundice or lipid blood, it can be measured by centrifugation to replace plasma (normal saline or dilution).
(5) WBC classification
Trichotomy. This question is often asked when I was a student, about the leukocyte classification histogram, from left to right, small cell population (mainly lymph), middle cell population (mainly mononuclear), large cell population (mainly neutral), people who have seen blood chips know that the volume of mononuclear is actually larger than neutral, why is the large cell population of the histogram neutral instead of mononuclear? Because when counting WBC, a hemolytic agent is added to lysate red blood cells, which can make the leukocyte plasma exude through the cell membrane, which is tightly wrapped around the nucleus or the presence of particulate matter, so that because the particles are supported, the neutrality containing particles is larger than the volume of mononuclear or lymph without particles, but the actual volume is not so. The leukocyte histogram does not represent its natural condition, but can be used to determine the distribution of the leukocyte mass population. Speaking of this, it can be found that LH750 has a particularly high classification of single cores, and microscopic examination finds that the actual single core is not high and neutral; sometimes re-examination, the classification can be normal. How can this be explained? It may be that some neutrals contain few particles and are dissolved without particle support, which is mistaken for a single nucleus. Personal opinions, do not be gullible.
Five classifications, known only as VCS counts, V is low-frequency waves, analyzing cell volume; C is high-frequency waves, analyzing cell karyotype; S laser, analyzing the particle characteristics of cells. Regarding histograms and scatter charts, I have a superficial understanding and need to continue to learn in my future work.
（6）HCT、MCV、MCH、MCHC
These indicators should be put together, because they are closely related to each other and can be linked together by formulas, so although they seem complex, there is actually a way to follow. By definition, HCT is the proportion of the volume of erythrocyte sedimentation to all blood volumes; MCV is the volume of each red blood cell; MCH is the amount of hemoglobin contained in each red blood cell; and MCHC is the concentration of hemoglobin contained in each red blood cell.
Therefore, MCV= HCT/RBC, MCH=HGB/RBC (remember that this formula can refer to the unit of MCH is pg, the unit of HGB and the unit of RBC, which is the molecule and which is the denominator should not be difficult to understand); MCHC = HGB/HCT (the unit is g/L is actually the concentration, so the denominator must have a volume, in fact, HCT is the specific product without units, the meaning can be). It should be noted that in the instrument, HCT is not measured, but through HCT = MCV × RBC, and MCV is measured, Kurt principle; MCH, MCHC are conversion indicators, not actual measurement, but it has an important prompt for judgment error. Understanding the origin of these indicators is very important for judging whether the results of RBC, HGB, and HCT are accurate. Illustration 4 needs to be explained by combining these indicators with the influencing factors mentioned earlier.
（7）RDW
RDW is interesting to combine RBC, HGB and MCV. We've all heard that, with the exception of iron deficiency, low MCV can suggest poor gene carriers. To identify poor and poor gene carriers, some people believe that RBC is normal, HGB is reduced, MCV is reduced, RDW is increased, iron deficiency poverty is considered; RBC is normal, HGB is reduced or normal, MCV is reduced, RDW is not increased, and poor gene carriers are considered. Some people also believe that joining the RDW to judge together may miss a large number of quiescent, light poor carriers, so it is advocated that the typical poor carrier blood routine is small red blood cells, red blood cell plethora, not anemia, there are the following rules: female RBC > 5.0, MCV5.5, MCV has not read the relevant literature, such as interest, recommended to read Zhang Junwu, Long Guifang "Hemoglobin and Hemoglobin Disease", Zeng Yitao "Human Hemoglobin", Southern Medical University Xu Xiangmin Thalassemia series papers, Guangzhou Maternal and Child Health Hospital Li Dongzhi, Liao Can thalassemia series papers. The final diagnosis of poverty depends on hemoglobin electrophoresis and genetic analysis.
(8) Platelet-related parameters
MPV, PCT, PDW, this series is somewhat similar to red blood cells, and its significance is not discussed much. The volume of each platelet in MPV is often used to identify the cause of PLT reduction: normal MPV is seen in the reduction of good bone marrow proliferation function; MPV reduction is seen in the reduction of abnormal bone marrow hematopoietic function. It is also used to evaluate the recovery of bone marrow hematopoietic function, and the general situation is that the MPV is low and the MPV is high.
Speaking of which, the indicators of the blood routine are basically finished. The following is a synthesis to analyze the several cases mentioned earlier.
1
EDTA-dependent platelet aggregation (points to watch the film), be sure to pay attention to the end of the film. That's all there is to it, the previous picture.
EDTA-dependent platelet aggregation
2
Analysis of the blood routine characteristics of condensation, how to find condensation? Severe condensation, when slowly tilting the test tube, can find that the red blood cells are fine sand particles, and even more frightening, there are even completely condensed into a huge blood clot, which needs to be shaken repeatedly to disperse. At the same time, there are also some condensations that are difficult to detect in appearance, which are mainly found in the characteristics of the blood routine. First of all, the principle of cold agglutination occurs, which refers to the presence of cold antibodies in the blood, after the blood is ex vivo, when the temperature drops, the cold antibody can bind to the erythrocyte surface antigen, so an antibody may bind to several red blood cells to form agglutination. May be seen in leukemia, lymphoma, mycoplasma pneumoniae infection, etc. Patients with this symptom should pay attention to keeping warm to prevent blood from accumulating and causing blood circulation disorders.
So what are the characteristics of condensation? According to the above principle, its distinctive feature is that RBC is reduced, accompanied by HGB is not low, the two are extremely inconsistent, MCV increases (the red blood cell mass formed by the cold antibody combined with red blood cells as mentioned earlier leads to a higher pulse), MCH, MCHC also increases, HCT is a conversion index, depending on RBC and MCV, generally often decreased. General water bath after the computer results can be normal (in line with clinical), should pay attention to take out the water bath box immediately on the machine, a moment can not be delayed. Extremely serious, you can consider centrifugation two or three times with normal saline or dilution of the same amount of plasma, and then water bath and then on the machine, generally can be alleviated, should pay attention to the error caused by the operation, suction and addition of the amount of unequal can cause changes in the concentration of relevant indicators, centrifugation is not in place can cause platelet reduction. Whether it is alleviated, mainly depends on the MCV, MCH, MCHC three no longer increase, that is, for the relief.
3
After the specimen is centrifuged, it can be seen that there is a flocculent white cloudy precipitate in the lower layer of the plasma, suspected to be fibrin (actually cold fibrinogen), and the biochemical tube can also be seen that there is a white cloudy precipitate in the serum, which should be cryoglobulin. Both are clarified after a water bath. Therefore, WBC, PLT pseudo-increase, is caused by the interference of cold fibrinogen (cryoglobulin), why these two are elevated at the same time, as mentioned earlier, the aggregation of platelets mainly affectSWBC, it can be imagined that this cold protein does not belong to WBC, nor does it belong to PLT, of course, it will affect both. Does it have an impact on RBC? Of course, there are, just the amount of this cold protein, which is mainly affected by the 109-level WBC and PLT, not the 1012-level RBC.
It should be pointed out that do not confuse condensation with cryoglobulinemia, cold fibrinogenemia, and condensation generally refers only to the agglutination of red blood cells, and these three belong to cold disease. Cold disease is a symptom secondary to the primary disease, not a diagnostic disease.
4
The answer to the inconsistency between HCT and HGB can also be obtained in the above-mentioned WBC, RBC influencing factors, HCT, MCV detection principles to get the answer. Because the patient WBC reached more than 400,000, 423.5 × 109/ L, a large number of neutrophils can be seen under the microscope, at this time the interference of WBC on RBC is relatively large, directly reflected in the MCV, a large number of WBC led to the increase of MCV, at this time MCV is not completely RBC's MCV, but affected by WBC, we know that WBC is larger than RBC, so MCV increases. And because WBC is extremely high, when detecting RBC, the order of magnitude of WBC is not as much as 750 times, so RBC is actually large, therefore, HCT = MCV × RBC, the latter two increase, HCT naturally increases. Therefore, the results of HCT are inaccurate, and HGB is relatively accurate, of course, at this time, HGB is affected by the high concentration of WBC interference, colorimetric optical path, so HGB is also increased, but the impact should not be particularly large, at this time the degree of anemia should also be HGB-based. At this point, you can safely answer the doubts raised by the clinic.
In summary, the above example talks about the error analysis of blood routine detection, in fact, these errors are not common in work from time to time, but through error analysis, you can more deeply understand each link and principle of the blood routine testing process, which is also quite beneficial for the analysis of abnormal blood routines. In practical work, we should also integrate theory with practice, pay special attention to the clinical situation of patients, and be able to combine with clinical practice at all times in order to issue high-quality blood routine reports.
Source: Coagulation factor 6
Edited by: Ran Reviewer: Rose
