Lost in calculation: the Clinical SYNTAX score goes logistic

This editorial refers to ‘Combined anatomical and clinical factors for the long-term risk stratification of patients undergoing percutaneous coronary intervention: the Logistic Clinical SYNTAX score’, by V. Farooq et al., doi:10.1093/eurheartj/ehs295 Cardiothoracic surgery pioneered the use of risk models in the reporting of operative results of patients referred to myocardial revascularization. Recently, interventional cardiology has rekindled its interest in constructing specific scores for long-term risk prediction of percutaneous coronary intervention (PCI). One of them, dubbed the SYNTAX score, is a successful model with website dissemination and extensive validation, in which the final score is calculated after coronary angiography by summing the scorings assigned to each individual lesion.1 Inherent limitations of the SYNTAX score, such as the lack of clinical or ischaemia information, have lately prompted its integration into more sophisticated algorithms with increased prognostic accuracy.2There are two ways in which a prognostic model may be useful in clinical decision-making. First, it may be collapsed by tertiles or arbitrary cut-offs to classify patients into risk categories. This knowledge assists in defining the threshold for a procedure and contributes to better resource allocation. Secondly, it can be used to estimate the prognosis of individual patients. These methods may be perceived as two ways to look at the same information, but they differ significantly. For instance, consider a category-based score (i.e. the SYNTAX score) which predicts that 19.2% of patients in the high-risk group will be deceased at 5 years from complex PCI. This model implies that among a large population of patients undergoing complex PCI, ∼19% of those categorized in the high-risk group will be dead after 5 years. Owing to the typical stochastic and time-dependent nature of prognostic models, classification into risk strata is frequently …