Serum Alkaline Phosphatase, Phosphate, and In-Hospital Mortality in Acute Ischemic Stroke Patients

Background The clinical impacts of serum alkaline phosphatase (ALP) and phosphate on early death are not fully understood in patients with acute ischemic stroke. We examined the associations between serum ALP, phosphate, and in-hospital mortality after ischemic stroke. Methods Serum ALP and phosphate were measured in 2944 ischemic stroke patients from 22 hospitals in Suzhou City from December 2013 to May 2014. Cox proportional hazard models and restricted cubic splines were used to estimate the relationships between serum ALP and phosphate (both as categorical and continuous variables) and risk of in-hospital mortality. Results During hospitalization, 111 patients (3.7%) died from all causes. After multivariable adjustment, the hazard ratio (HR) of the highest quartile compared with the lowest quartile of ALP was 2.19 (95% confidence interval [CI], 1.20-4.00) for early death. Restricted cubic spline analysis indicated a significant linear association between ALP and death ( P -linearity = .017). A U-shaped association of phosphate with in-hospital mortality was observed ( P -nonlinearity = .011). Compared with the third quartile of phosphate (1.08-1.21 mmol/L), HRs of the lowest and highest quartiles for early death were 2.17 (1.15-4.08) and 1.70 (.88-3.30), respectively. Sensitivity analyses further confirmed our findings. Conclusions We observed a graded relationship between serum ALP levels and risk of early death in patients with acute ischemic stroke. There was a U-shaped association between phosphate and all-cause mortality with significantly increased risk among patients with lower phosphate levels.