Evaluation of the prognosis of patients with CHF is critical to allow clinicians to select appropriate treatment strategies accurately. In this study, the PRO-driven models that we developed and validated showed good performance for event prediction in patients with CHF. Importantly, these models only require variables can be implemented after discharge. Moreover, we introduced SHAP approach and established a self-made web-based risk calculator, which could predict the prognosis of each individual, to explain the black box of ML models. To our knowledge, this is one of only a few studies that focus on prognosis models in CHF mainly using information gathered through PROs.
This study demonstrated that CHF-PRO had high predictive value for mortality and HF readmission in patients with CHF. Previous studies have also confirmed that PRO is an essential prognosis indicator for HF even adjusting for traditional variables [6, 8]. Moreover, PRO has also been applied as one of the predictor variables to establish the prognosis model of CHF. Different from the previous studies, we constructed prognosis models primarily based on the information of CHF-PRO and obtained a good predictive effect in this study. This is consistent with our previous study concerning a readmission model through logistic regression [24]. The data on all the indicators applied in this study could be obtained through telephone or self-test, which is expected to provide a feasible prediction and guidance tool for the out-of-hospital management of patients with CHF. Among the four domains of CHF-PRO, physical status was the strongest predictor in this study. In addition, the remaining subscales of CHF-PRO also proved to be important for accurate prediction. This supports the findings of previous studies [25]. Providing relief for the physical symptoms is one of the most important goals of CHF treatment, but the psychological status and social factors of patients with CHF should also be considered during the clinical application.
We found that ML methods failed to improve the discrimination ability of logistic regression. A meta-analysis that used AUC to measure the performance of models from 71 studies confirmed that there was no evidence of superior performance of ML over logistic regression [26]. However, in this study we found that the parameter adjustment significantly improved the accuracy of probability and discrimination of ML, except that in logistic regression. This observation may be attributed to the logistic regression being specialized in linear data processing, and the possible adjustments to parameters are limited. The result reminds that when applying the ML methods to the complex data, we could improve the model performance through parameter adjustment. Among all the ML, the XGBoost algorithm had the highest predictive performance in our study. XGBoost is a decision-tree-based algorithm and composed of a series of base classifiers such as decision tree, k-nearest neighbor, support vector machines, and logistic regression. The base classifiers are linearly superimposed to optimize the algorithm after they are determined [17]. Studies showed the XGBoost model offers strong generalization ability, high scalability, and fast computing speed in model building [27]. XGBoost typically shows outstanding performance when dealing with complex problems. It is suitable for almost all types of complex classification problems [24–26] and showed good predictive value in many studies on prognosis models [27, 31].
Additionally, the black box of ML was opened by interpretability techniques in this study. Through SHAP algorithm, we can understand the relationship between predictors and outcomes in the XGBoost models. The contributions of the variables for each individual could be obtained from the result of SHAP, which helps better understand the decision-making process of the model and facilitate its use in clinical setting [32]. Meanwhile, a self-made web-based risk calculator was established in this study. Through the calculator, we could easily get the incidence rates of outcomes and identify patients with the high risk. From these two interpretable algorithms, we can identify both high-risk factors and high-risk individuals, which provided unique tools to better guide clinical decision making.
Despite many advantages of the models, some limitations remain. First, the MACEs in our study only included all causes of death and HF readmission that were clear during our follow-up process. This led to incomplete analysis results. Second, the data of our study were mainly from the Shanxi Province of China, which limits generalizability and requires further validation in other populations. Finally, the clinical data was not included in the models of this study. In the following studies, we will establish a prognosis model using the data of clinical indicators and CHF-PRO in our further studies.