Author: Guo Suli
Unit: The Sixth Medical Center of the Plaster General Hospital
Blood routine is an indispensable test link in our routine work, I believe that everyone is no stranger. There are many factors that affect blood counts, in addition to common reasons such as platelet aggregation caused by unsmooth blood draw before the test, specimen hemolysis, and the effect of lipid blood on red blood cells and hemoglobin, red blood cell condensation, EDTA antagonism, and the influence of drugs on the test results are also common in daily testing work.
Therefore, how to ensure the quality of the test results and provide accurate and reliable test results for the clinic requires our test people to have a pair of eyes.
Case after
Patient, male, 63 years old. On November 6, 2021, due to lung infection, thrombocytopenia was transferred from the outer hospital to our hospital for treatment.
The test items carried out on the same day were: four urgent blood coagulation items, emergency investigation of infection combinations, and urgent blood routine.
Laboratory tests showed that the four coagulation items were within the normal range, the CRP was 6.7 mg/L, mildly elevated, IL-6 and PCT were normal, the respiratory pathogen spectrum was normal, and the blood routine results were abnormal.
After communicating with the clinician, it was found that the patient's blood routine results on October 28 were normal, and the results on November 6 had shown abnormalities (condensation). During this period, due to the diagnosis of lung infection, cephalosporin antibiotics were taken for treatment. Due to the diagnosis of thrombocytopenia in the outer hospital on November 6, he was immediately transferred to our hospital for treatment. The patient was otherwise well, communicated with the hematology department, and also excluded ITP.
Case studies
Figure 1
Then the question comes, what do you think when you see this report sheet? Can reports be sent directly? What is the reason why I can't send it? And what to do? Well, with these questions, let's analyze and analyze it with Xiaobian.
First of all, the red direct measurement parameters (RBC, HGB, HCT) are reduced, the calculation parameters (MHC, MCHC) are increased, and the platelet count is reduced, and this report must not be sent at the first time. There are several knowledge points involved here:
1. In the results, RBC, HGB, HCT do not meet the "3 rules", that is, 3 * RBC = HGB, 3 * HGB = HCT, the clinical allowable error is ±3%, where the RBC falseness is reduced, the calculated value MHC, MCHC pseudo-increase, then the specimen condensation is highly suspected;
2. According to Article 13 of the re-examination rules recommended by ICSH, when the MCHC exceeds the normal upper limit of 20g/L, it requires re-examination. The specimen is examined for lipid blood, hemolysis, agglutination, and spherical erythrocytes. According to this rule, specimen condensation phenomena or other abnormal specimens can be found.
3. For the first patient, PLT reduction requires push-lens microscopy, excluding the slight agglutination caused by naked eye or blood draw failure, and to be highly vigilant against the false reduction of PLT caused by EDTA antagonism to prevent misdiagnosis.
After reading the above problem solving ideas, I believe that everyone has their own treatment plan at this time. Yes, first observe the status of the specimen, there is no clot on the appearance, and there are no wall-hanging particles on the tube. Incubation is carried out after excluding the cause of blood draw, and microscopy is pushed at the same time, see Figure 2.
Figure 2
Microscopic results: it shows that platelets are massively aggregated, and red blood cells are not agglomerated.
At this time, everyone is not very sure that in addition to condensation, the specimen may also be accompanied by EDTA antagonism. However, by looking up the literature, there are not many cases of PLT reduction caused by EDTA antagonism, and the real reasons need to be read down.
Next, we found the coagulation vessels sent by the patient with the blood routine, mixed them well and then put on the machine, the results are as follows, see Figure 3.
Figure 3
Based on the above results, we can see that the PLT is not corrected, but is lower. Thus, it is essentially possible to exclude a reduction in PLT caused by EDTA antagonism.
In fact, we also re-sampled heparin tubes to support this, which is in line with the speculation. Secondly, the erythroid results detected by the sodium citrate tube were lower, and the RBC, HGB, and HCT did not meet the "3 rules" more prominently, because the time difference between the two detection time was about 1 hour, and the phenomenon of cold agglutination of red blood cells was more obvious at this time.
Next, looking at our incubation results, we put the blood sample in the incubator and tested it every half an hour, and found that the condensation results were not well corrected, and the value of platelets could not be accurately measured. Immediately after, we begin to perform plasma exchange on the specimen, wash off the cold agglutinin, and retest, as shown in Figure 4.
Figure 4
At this point, the condensation phenomenon is basically corrected, and the platelets are critical! Carefully analyze the reasons, consider that most of them are due to the operator's irregular operation, and multiple plasma exchanges suck away the white membrane layer (including platelets) between the plasma and the red blood cell layer, resulting in a false reduction of platelets.
Until now, plasma exchange has corrected the condensation, but the problem of thrombocytopenia has not been corrected. So we proceeded with the 1:7 dilution of peripheral blood (without anticoagulants) tested in dilution mode, and the results are shown in Figure 5.
Figure 5
Seeing this now, I think everyone has a clear understanding of what results should be sent in the end. Yes, the final 1:7 dilution of the peripheral blood after 10min of incubation is the final result.
But do you still have a question, why do platelets decrease? Does the patient really have thrombocytopenia? The answer is undoubtedly no.
This can initially be roughly judged by microscopic platelets, because of the reduction in falsehood caused by aggregation, and then you only need to correct the platelet count.
In fact, we finally learned that the patient had taken cefazoxime combined with moxifloxacin anti-infective therapy during the period, and the blood routine was retested for a period of time after the drug was discontinued, and the results of the intravenous blood test without special treatment returned to normal.
After searching for relevant literature, it was found that there had been condensation and platelet aggregation caused by taking ceftriaxone sodium, so the existence of cold agglutination caused by cephalosporin antibiotics was not excluded, nor was it excluded that the phenomenon of condensation caused by other infectious factors was not excluded.
Case summary
Condensation is mainly caused by cold agglutinin antibodies, which are essentially IgM antibodies against erythrocyte antigens. There are low-potency cold agglutinins in the normal human body, and agglutination can generally occur below 16 °C, and no agglutination occurs above 30 °C.
If the bacterial infection, especially mycoplasma infection or some autoimmune hemolytic diseases, it can produce high-efficiency valence cold agglutinin, so that the blood after leaving the body is prone to condensation, especially at 4 °C, the performance is the strongest, so that the test results are distorted.
As an examiner, you must have the ability to identify at a glance whether the specimen has condensation. Secondly, for patients with thrombocytopenia, especially those who come to the hospital for the first time, in addition to paying attention to the patient's clinical diagnosis and asking about the medical history, it is necessary to push the lens for microscopy, because microscopy is the "gold standard" of the test results. Instead of simply reviewing it again, the remarks on the "result review consistent" sent, this is an extremely irresponsible performance, easy to make the doctor misjudge, serious will endanger the patient's life, should be paid attention to!
【Reference】
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Source: Voice of Inspection
Edited by: Yeah Reviewer: Xiao Ran