No statistically significant association between log-transformed fibrosis-4 index and major adverse cardiovascular events in patients with acute coronary syndrome undergoing percutaneous coronary intervention

The Fibrosis-4 index is a routinely obtainable composite marker derived from age, aspartate aminotransferase, alanine aminotransferase, and platelet count. Although higher FIB-4 levels have been associated with adverse cardiovascular outcomes, the association between log-transformed FIB-4 and major adverse cardiovascular events in patients with acute coronary syndrome undergoing percutaneous coronary intervention remains incompletely characterized. This single-center retrospective cohort study included 368 patients with acute coronary syndrome who underwent percutaneous coronary intervention. The primary exposure was natural log-transformed FIB-4, referred to as lnFIB-4. The primary outcome was major adverse cardiovascular events, defined as a composite of cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, unplanned repeat revascularization, and hospitalization for heart failure. Cox proportional hazards models were used to evaluate the association between lnFIB-4 and MACE. The primary multivariable model adjusted for age, sex, GRACE score, left ventricular ejection fraction, and body mass index and was conducted using complete-case data from 350 patients. Restricted cubic spline and exploratory two-piecewise Cox analyses were performed to characterize the exposure-response pattern. Among 368 patients, 131 experienced MACE during follow-up. The prespecified primary multivariable analysis included 350 patients with complete data for all model covariates. lnFIB-4 was not statistically significantly associated with MACE in the primary model (HR per 1-unit increase, 1.300; 95% CI, 0.992–1.704; P = 0.057). The association also remained non-significant in the expanded multivariable model (HR, 1.24; 95% CI, 0.96–1.60; P = 0.096). Restricted cubic spline analysis showed no statistical evidence of nonlinearity (P for nonlinearity = 0.856). In an exploratory data-driven two-piecewise analysis, a possible inflection point was identified at lnFIB-4 = 0.60; above this value, the estimated HR was 1.47 (95% CI, 1.10–1.96; P = 0.009). This threshold finding was exploratory and should not be interpreted as a validated clinical cut-off. In patients with ACS undergoing PCI, lnFIB-4 was not statistically significantly associated with MACE in the prespecified primary multivariable analysis. Restricted cubic spline analysis did not provide evidence of nonlinearity. Exploratory two-piecewise analysis identified a possible data-driven change-point, but this finding should be considered hypothesis-generating rather than confirmatory. Larger multicenter prospective studies are needed to determine whether lnFIB-4 has independent or incremental prognostic value in this population.