CD is characterized by blood coagulation dysfunction induced by abnormal fibrinogen molecular structure. Fibrinogen plays an important role in the coagulation process; first, thrombin recognizes and cleaves to the peptide bond of fibrinogen AαArg16-Gly17 and BβArg14-Gly15, and releases fibrin peptides A and B from the Aα and Bβ chains, respectively to form fibrin monomers. Second, fibrin monomers aggregate to form a soluble fibrin gel. Finally, with the help of coagulation factor ⅩⅢ and calcium, it is further cross-linked to form a stable fibrin clot. The physical properties of the blood clot (rate, hardness, and stability) will determine whether the patient has normal coagulation function or whether there will be bleeding or thrombosis [11,12]. TEG is an indicator that reflects the dynamic changes in blood coagulation, including the formation speed of fibrin, the dissolution state, the firmness and elasticity of coagulation. Therefore, it is widely used in the screening of various coagulation abnormalities pre- and post-operatively, to guide blood transfusion and medication [13]. It has also been widely used for the screening in CD diseases. It is of great value in the diagnosis, differential diagnosis, and evaluation of the coagulation status of CD patients, and provides more accurate information for the therapy of CD patients [14,15]. TEG can also be used to assess the risk of obstetric complications in women with dysfibrinogenemia (or hypodysfibrinogenemia) in the non-pregnant state [8]. Therefore, choosing a suitable vacutainer tube for TEG measurement and obtaining accurate and reliable experimental results are necessary for assessing the risk of bleeding or thrombosis in CD patients.

In this study, we used both Ruiqi and BD sodium citrate anticoagulation tubes to collect venous whole blood from CD patients and healthy controls for TEG measurement. The main monitoring indicators included R, K, angle, minimum amplitude (MA), LY30, and CI. When the Ruiqi vacutainer tube was used, significant differences were found in R, LY30, and CI between CD patients and healthy controls. When the BD vacutainer tube was used, differences occurred in R and CI between CD patients and healthy controls. The results showed that when the same sodium citrate vacuum blood collection tube was used, the R, measured by TEG in CD patients was shorter than that of healthy controls, whereas their CI was higher than that of healthy controls. R value refers to the time from the beginning of the detection to the amplitude of up to 20mm. This mainly reflects the comprehensive effect of all coagulation factors participating in the coagulation process, and can be used to reflect the activity of the coagulation factors. CI is the coagulation comprehensive index, which is used to describe the overall coagulation status of the patient. CI≤3 is considered as a hypocoagulable state, and CI≥3 is considered as the hypercoagulable state. CI is calculated based on R, K, angle, and MA. When the R time is shortened, CI is increased, indicating that the coagulation factor activity is strong and that the body is in a hypercoagulable state.

In CD patients, significant differences occurred in R, angle, and CI between Ruiqi and BD vacutainer tubes. In healthy controls, the differences in R, K, angle, LY30, and CI were statistically significant between Ruiqi and BD vacutainer tubes (P<0.05). This study showed that these two brands of blood collection tubes have a certain impact on TEG measurements in both CD patients and healthy controls; this is consistent with the results reported by Chinese scholars [16]. The sodium citrate vacuum blood collection tube produced by China Ruiqi Company, and used in this study, is made of single-layer glass, with a sodium citrate concentration of 0.109 M (3.2%) and a blood collection volume of 1.8 mL. When the blood specimen was collected, there was a 3 mL “dead space”. BD vacutainer tube is a small volume thick-walled double siliconized inner wall vacuum blood collection tube with a sodium citrate concentration of 0.109 M (3.2%), the blood volume of 2.7 mL, and almost no "dead space" after blood sampling. Studies have shown that the "dead space" of the sodium citrate vacuum blood collection tube can lead to partially activated and aggregated platelets, reduced coagulation factor Ⅹa activity, shortened activated partial thromboplastin time, and ultimately, reduced R value [17]. Studies have also shown that the high concentration of magnesium ions in the rubber stopper of the vacuum blood collection tube can activate certain coagulation factors, resulting in shortened prothrombin time and international normalized ratio measurements [18,19]. Since the quality of the blood collection tubes varies from manufacturer to manufacturer, this can lead to different magnesium ion concentrations in the rubber stoppers, and to inaccurate TEG results. Some scholars suggested that the magnesium ion concentration in the vacutainer tube should be less than 1 mmol/L [20]. In addition to the magnesium contamination, changes in the sodium citrate concentrations are other sources of pre-analysis errors. The anticoagulant concentration recommended by the National Committee for Clinical Laboratory Standardization (NCCLS) is 3.2% or 3.8% (equivalent to 0.109 mol/L or 0.129 mol/L), and the ratio of the anticoagulant to blood is 1:9. The sodium citrate vacuum blood collection tube maintains a stable vacuum to ensure that the ratio of blood to anticoagulant in the tube cannot be affected. The sodium citrate in the anticoagulant acts mainly as an anticoagulant by chelating with calcium ions in the blood sample. When the ratio of the anticoagulant is too low, it will increase the absolute concentration of calcium ions and shorten the clotting time. The K value reflects the coefficient of fibrin and platelets at the beginning of the clot formation, that is, it reflects the rate of clot formation. The K value is mainly affected by the level of fibrinogen, accounting for about 80%, and it is also affected by the function of the platelets, accounting for about 20%. The angle value is the result of the coefficient of fibrin and platelets at the beginning of the clot formation. It is closely related to the K value and reflects the rate of blood coagulation. In this study, the angle value measured by the Ruiqi vacutainer tube was larger than that of the BD vacutainer tube in both CD patients and healthy controls. The "dead space" of the vacutainer tube can cause the platelet to be partially activated and aggregate, which leads to an increase in the angle.

In this article, Ruiqi and BD sodium citrate vacuum blood collection tubes were used to measure TEG in CD patients and healthy controls, and then their parameters were compared. It was found that the R value of Ruiqi vacuum vascular collection was lower, the angle was larger, and its CI was lower than that of BD vacuum blood collection tubes in both CD patients and healthy controls. The plug of the BD vacuum blood collection tube was treated with low magnesium to prevent the activation of coagulation factors, and the double-layer tube wall helped to maintain its vacuum, and to effectively maintain the ratio of the anticoagulant to the blood. The clinical manifestations of CD patients are diverse, the TEG measurement helps to assess the blood coagulation level accurately, to assess the risk of bleeding or thrombosis, and provide guidance for the patient's replacement therapy. Therefore, it is necessary to choose a suitable vacutainer tube for TEG measurement and establish the TEG reference range for the laboratory, so as to provide accurate experimental data for the clinic.

Acknowledgments:

We would like to thank the Department of Hematology and Clinical Laboratory of the First Affiliated Hospital of Guangxi Medical University, China. We are grateful to all participants in this study.

Research funding:

This research was funded by the National Natural Science Foundation of China (grant number:81800130)

Author contributions:

Xiang Liqun analyzed the study data and wrote the initial draft of the paper; Luo Meiling designed the study; Wu Yangyang statistical experiment data; Yan Jie and Lin Faquan revised the article. All authors have accepted responsibility for the entire content of this manuscript and approved its submission.

Competing interests: The authors have no conflicts of interest to disclose.

Informed consent: Informed consent was obtained from all individuals included in this study.

Ethical approval:

This study was approved by the Medical Ethics Committee of No.6, Shuangyoyng Road, Qingxiu District, Nanning City, Guangxi, China.