PICC has emerged as the primary vascular access for children with hematological malignancies to receive chemotherapy, long-term intravenous fluids, and nutritional support due to its simple operation, good safety, high success rate, long retention time, and low discomfort(21, 22). However, what cannot be ignored is that PICC-related thrombosis has been one of the most common and serious complications. Our results showed that the total incidence of PICC-related thrombosis in children with hematological malignancies was 18.9%, consistent with previous studies(14–16). Early identification of individuals at risk and timely intervention are pivotal in avoiding thrombosis. Currently, however, there is a lack of proprietary assessment tools for children with hematological malignancies. Hence, this study pioneered the development of a nomogram model for predicting PICC-related thrombosis in children with hematological malignancies. The model, which consists of six highly correlated risk factors, showed better predictive performance in both the training and validation sets, with good discrimination, calibration degree, and clinical applicability.
In our study, leukemia was one of the strongest risk factors predicting PICC-related thrombosis in children with hematological malignancies. Leukemia stands as the most prevalent malignancy in children and has a higher incidence of venous thromboembolism (VTE) compared to solid tumors(23, 24). Activation of the coagulation system may be the most important pathogenic factor in leukemia-associated VTE. In the acute leukemic state, abnormally proliferating leukemic cells not only affect the normal hematopoietic function and disturb the internal environment of the child but also contain procoagulants released into the bloodstream(25). In addition, asparaginase, which is the backbone of the chemotherapy regimen for children with leukemia, leads to a decrease in naturally occurring anticoagulants (e.g., protein C, protein S, and antithrombin), and consequently to an increase in thrombin production(26, 27). When child with leukemia has an indwelling PICC, it is more likely to contribute to the further development of a hypercoagulable state of the blood and trigger a thromboembolic mechanism.
PICC catheters are usually made of silicone or special polyurethane that has good tissue compatibility(28). After entering the blood vessels, the temperature of the human body makes it softer and thus less irritating to the vessel. However, this synthetic material is also thought to have the potential to activate the coagulation process due to its lack of an endothelial layer that inhibits platelet coagulation and adhesion(29). The greater the number of catheters, the higher the risk of thrombosis. In addition, multiple catheterizations directly increase the opportunity for vascular intima injury, which also raises the incidence of thrombosis(30). Furthermore, children with multiple catheters were usually more critically ill and needed bed rest for longer periods, which inevitably leads to restricted limb movement, reduced skeletal muscle contraction, muscle relaxation, and weakened vascular support, which leads to slower blood flow and contributes to the formation of PICC-related thrombosis(19, 31).
We observed that the history of catheterization can increase the risk of PICC-related thrombosis in children with hematological malignancies, consistent with the results of Badheka et al.(32) and Shin et al(16). This may be related to venous stenosis caused by catheters through various pathways, including mechanical injury, infection, foreign object stimulation, and abnormal vascular wall damage repair process(33, 34). These factors usually interact with each other and contribute to the development and formation of stenosis. Consequently, when a PICC is placed again in the same limb, it may exacerbate the slow blood flow caused by the venous stenosis and increase the likelihood of blood flow turbulence. This altered hemodynamics can make it easier for blood to form a relatively static area at the stenosis, thus promoting PICC-related thrombosis(35). In addition, stenosis increases the catheter-to-vein ratio, and makes contact and friction between the PICC and the vessel wall more frequent, which may cause damage and further activate the process of clot formation(14).
TPN refers to the provision of all daily nutrient requirements by intravenous infusion. Previous studies have shown a significantly higher incidence of thrombosis in children with intestinal disorders who were placed on central venous catheters for long-term TPN(36). In our study, most of the children requiring TPN did not have concomitant intestinal disease and needed only short- to medium-term TPN. Nevertheless, the results of this study suggest that TPN remains a significant risk factor for PICC-related thrombosis. Firstly, TPN mixtures generally contain high concentrations of glucose, amino acids, and fat emulsion, which may alter plasma osmolality and increase blood viscosity, thereby increasing resistance to blood flow. Additionally, components such as glucose in TPN mixtures may favor the procoagulant state of monocytes(37). Moreover, calcium, one of the major ions in the TPN mixture, is an essential activator of the coagulation cascade, and its supplementation promotes activation of the coagulation cascade and increases the risk of thrombosis(38).
FIB is a protein with coagulant function involved in the body’s coagulation and hemostatic processes. As the most abundant coagulation factor in plasma, the normal levels range from 1.5 to 3.5 g/L(39). D-dimer is a soluble fibrin degradation product derived from plasmin-mediated degradation of cross-linked fibrin. Its elevated concentration represents activation of the coagulation system and secondary hyperfibrinolysis in the body(40). Both of these indicators can reflect the hypercoagulable state of blood. The results of this study showed that FIB concentration and D-dimer concentration after catheterization were the two most critical risk factors for PICC-related thrombosis in children with hematological malignancies, and children with high concentrations were more likely to develop thrombosis. Therefore, after PICC placement, healthcare professionals should routinely screen children for FIB and D-dimer concentrations. Children with high or persistently elevated levels of both indicators should be alerted to the development of PICC-related thrombosis and given appropriate prophylactic anticoagulant therapy. It is worth noting that even though FIB and D-dimer have certain applications in the diagnosis of thrombosis(41–43), they cannot be the only indicators to confirm the diagnosis of thrombosis. The risk of thrombosis should be assessed in conjunction with other key risk factors.
In this study, we constructed the first PICC-related thrombosis prediction model for children with hematological malignancies and visualized the risk prediction results of the model using a nomogram, which has good discrimination, calibration degree, and clinical applicability. The model can be used as an effective assessment tool for PICC-related thrombosis in children with hematological malignancies, providing useful predictive information for clinical staff and parents of children. Through focused monitoring and active intervention in high-risk children, the occurrence of PICC-related thrombosis can be effectively reduced, and unnecessary complications and treatment delays can be avoided. This will simultaneously help improve the efficiency of healthcare resource utilization and reduce the burden on patients and the healthcare system.
Nevertheless, this study also has some limitations. (1) The construction of the model was based on retrospective data, which may have selection bias, missing data, and incompleteness. (2) The sample size was relatively limited and all were from the same medical center, which may affect the stability of the model and require caution in interpreting the findings. (3) When establishing the model, multiple continuous variables were converted to categorical variables for clinical convenience, which to some extent resulted in a loss of information and may affect the accuracy of the model. (4) Lack of external validation makes it impossible to understand the generalization performance of the model on new datasets. (5) The number of factors included in our study was limited, and the relationship between other relevant factors and the risk of PICC-related thrombosis is still unclear. Therefore, future studies with larger sample sizes of children with hematological malignancies are needed to determine whether factors other than those already in the model are independently associated with PICC-related thrombosis to further optimize and update our model.