Xiong W, Zhao Y, Xiong Y, et al. - Whether coagulation factor IV, also recognized as serum ionized calcium (SIC), can serve as an indicator of symptomatic pulmonary embolism (PE) due to primary lung cancer(LC), was determined in this study including 388 patients who had CTPA and /or radionuclide ventilation perfusion scanning because of PE-suspected symptoms. Researchers stratified these patients into LCPE (lung cancer and PE) group (n = 95), PE group (n = 99), LC group (n = 98) and control group (n = 96). They found that LCPE group had the highest SIC among four groups at admission. Among four groups, the LCPE group had the highest level change of SIC from admission to discharge. For a diagnosis of PE among LC patients, a sensitivity of 71.9% and a specificity of 86.0% were yielded by SIC in a ROC curve analysis. The AUC was 0.781. Findings revealed the likely value of SIC as an indicator of PE in patients with primary LC.