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.