Does smoking status affect the association between baseline white blood cell count and in-hospital mortality of patients presented with Acute Coronary Syndrome? The Greek study of Acute Coronary Syndromes (GREECS)

Objectives In this work, we sought to investigate whether smoking status modifies the effect of white blood cell count (WBC) on in-hospital mortality of patients presented with acute coronary syndrome (ACS). Methods A sample of 6 hospitals located in Greek urban and rural regions was selected. We recorded almost all consecutive patients due to ACS, from October 2003 to September 2004 (2172 patients). Results The mean (standard deviation) WBC count was 9.14 (3.16) cells/dL. The in-hospital mortality rate was higher in patients of upper tertile compared to those of lower tertile of WBC (p < 0.05). The interaction between smoking status and WBC count revealed that smoking status modifies the effect of WBC count on mortality (p for interaction = 0.004). Thus, stratified analysis showed that the WBC count is an independent predictor of in-hospital mortality only among former and current smokers. Conclusions We demonstrated that the association between WBC count and mortality modified by smoking status and that WBC count is a predictor of mortality only among former and current smokers.