Author: Zhang Qingxu Xiao Bo
Unit: Department of Clinical Laboratory, Second People's Hospital of Changzhi City
In recent years, malignant tumors seriously threaten people's health, and timely detection, early diagnosis and treatment in the early stage of disease development can effectively reduce mortality.
Tumor markers (tumor makers, TMs) are present in malignant tumor cells, or in the process of disease occurrence and development, due to abnormal proliferation of malignant tumor cells, produced by certain abnormal substances. It has certain value for the occurrence and development of cancer, as well as the prognosis of treatment, and the monitoring and evaluation of efficacy [1].
In addition to some specific indicators, other individual items of detection will be limited in the diagnosis and identification of malignant tumors, so in order to be able to quickly and accurately diagnose cancer, it is recommended that multiple tumor marker indicators be tested jointly and dynamically monitored [2].
At present, the C-12 detection system instruments used in our hospital include SLP-OO1B automatic biochip reader, biochip image analysis system software and C-12 kit. The existing detection chips have male core and female core, of which the male core detection items include PGI, PGII, CA199, AFP, PSA, F-PSA, NSE, Cyfra21-1, CA125, CEA, CA724 and Pro-GRP, female core detection items include PGI, PGII, CA199, AFP, NSE, β-HCG, Cyfra21-1, CEA, CA724, CA125, Pro-GRP and CA153.
These projects basically cover the main indicators needed in the current clinic and provide a favorable guarantee for clinical diagnosis. Therefore, tumor markers have gradually become a "sharp weapon" for tumor-related disease screening and postoperative treatment effect monitoring. However, in the clinical test work, this "sharp weapon" should also be used cautiously, after all, it also has blunt times, as the "master" of the "sharp weapon", if the tester does not find it in time, the test result may make the clinician scratch his ears and scratch his cheeks, so that the patient will increase his troubles.
1
Case sharing
The patient, female, 70 years old, came to our rheumatology department on February 10, 2021 for rheumatoid arthritis.
The examination items on the day were blood routine, coagulation series, biochemical routine items, ANA spectrum, ANA and AKA, CCP, RF, C-12, etc., of which antinuclear antibody cytoplasmic fibrosis, antinuclear antibody titer 1:320, AKA negative, CCP161.8U/mL, anti-nuclear antibody spectrum positive anti-Ro-52 antibody, other items negative, RF382IU/mL, C-12 results appeared positive. Communicate with the clinician that the patient has no history of cancer, has mass lesions in the lungs, is normal for whole-body CT, and has normal results for pathological tissue slices.
By communicating with the superior inspector, looking at the original results and data, the negative array was found to be reactive:
Initial examination results
We tested the dilution of serum 4 times and 8 times with normal saline, respectively, and found that some of the results were not linear. After discussion with the engineer, the serum was diluted 3 times with the matching reinforced dilution IV number, and the treated serum was tested again, and the results were compared as follows.
Top: Enhanced dilution 3 times; Medium: normal saline dilution 4 times; Bottom: normal saline dilution 8 times
After a series of treatments, the correct results were finally obtained, and considering the limitations of the patient's rheumatoid arthritis and microarray chemiluminescence methodology, it was suspected that there was a cross-reaction caused by RF, etc.
So why do false positive results occur? How does Enhanced Diluent IV remove interference? This has to start with tumor protein chip technology...
2
Tumor protein chip technology
The rapid development of protein chip technology provides an ideal tool for the joint detection of multiple TM indicators. In clinical research, this technology provides a favorable basis for the early diagnosis of cancer.
Tumor protein chip is a tumor screening laboratory technology established on the basic research idea of joint detection of multiple indicators, giving full play to the advantages of protein chip high throughput, high sensitivity, speed and trace amount. A comprehensive analysis of common tumors was performed by measuring trace amounts of serum and quantitatively detecting the content of 12 tumor markers in the detected serum [3].
C-12 detection system is based on the integration of immunology and biological signals, using the characteristics of specific binding of antigens and antibodies, coated on the solid-phase matrix with monoclonal antibodies bound to a variety of tumor markers, to capture potential corresponding antigens in serum samples Through its high-sensitivity tracing technology, the biological signals generated are converted into optical and electrical signals, so as to achieve the purpose of quantitative detection [4], the reaction schematic diagram is shown in Figure 3.
The C-12 detection system is based on the integration of immunology and biological signaling, using the characteristics of specific binding of antigens and antibodies, and coating the solid-phase matrix with monoclonal antibodies binding multiple tumor markers to capture potential corresponding antigens in serum samples. Through its high-sensitivity tracing technology, the resulting biological signal is converted into optical and electrical signals, so as to achieve the purpose of quantitative detection [4], and the reaction diagram is as follows.
Schematic diagram of double antibody sandwich method
3
How do blockers work?
The main component of the reinforced dilution IV is MAK-33-IgG-poly, in order to eliminate the excess binding between the solid phase and the detected component, a blocker is added, a competitive binding interfering substance is added, thereby blocking the production of unintended binding, the reaction diagram is as follows.
Schematic diagram of interference exclusion processing
【Reference】
Jiang Yanmei, et al., Significance of protein chip multi-tumor marker detection in tumor screening in healthy physical examination population. Chinese Journal of Immunology, 2020. 36(12): p. 1499-1504.
[2] Eggeling, F.V., et al., Tissue-specific microdissection coupled with ProteinChip array technologies: applications in cancer research. Biotechniques, 2000. 29(5): p. 1066-1070.
Qi Jun, Protein chip technology and its application in tumor laboratory diagnosis. Chinese Journal of Laboratory Medicine, 2003. 26(10): p. 2.
[4] Weinberger, S.R., E.A. Dalmasso, and E.T. Fung, Current achievements using ProteinChip Array technology. Current Opinion in Chemical Biology, 2002.
Edited by: Yeah Reviewer: Xiao Ran