Prognostic impact of alkaline phosphatase for in-hospital mortality in patients with acute coronary syndrome: a prospective cohort study in China

OBJECTIVES: Alkaline phosphatase (ALP) can promote vascular calcification, but the association between ALP and in-hospital mortality in patients with acute coronary syndrome (ACS) is not well defined. DESIGN: A prospective cohort study. SETTING AND PARTICIPANTS: A total of 6368 patients with ACS undergoing percutaneous coronary intervention (PCI) from 1 January 2010 to 31 December 2017 were analysed. MAIN OUTCOME MEASURES: In-hospital mortality was used in this study. RESULTS: ALP was analysed both as a continuous variable and according to three categories. After multivariable adjustment, in-hospital mortality was significantly higher in Tertile 3 group (ALP＞85 U/L) (OR: 2.399, 95% CI 1.080 to 5.333, p=0.032), compared with other two groups (Tertile 1: ＜66 U/L; Tertile 2: 66–85 U/L). When ALP was evaluated as a continuous variable, after multivariable adjustment, the ALP level was associated with an increased risk of in-hospital mortality (OR: 1.011, 95% CI 1.002 to 1.020, p=0.014). C-statistic of ALP for predicting in-hospital mortality was 0.630 (95% CI 0.618 to 0.642, p=0.001). The cut-off value was 72 U/L with a sensitivity of 0.764 and a specificity of 0.468. However, ALP could not significantly improve the prognostic performance of Global Registry of Acute Coronary Events (GRACE) score (GRACE score+ALP vs GRACE score: C-statistic: z=0.485, p=0.628; integrated discrimination improvement: 0.014, p=0.056; net reclassification improvement: 0.020, p=0.630). CONCLUSIONS: In patients with ACS undergoing PCI, ALP was an independent predictor of in-hospital mortality. But it could not improve the prognostic performance of GRACE score.