RESULTS: Medians of D-dimer of patients in three subgroups with normal renal function, mild renal impairment and moderate renal impairment were 291.5, 995.5 and 1901.5 μg/L (P<0.001), respectively. The sensitivity of negative D-dimer to rule out PE was considered of 99%—100% in the three subgroups. While, the specificity of that was 70%, 42% and 23%. The number of patients needed to test (NNT) to obtain one negative test of D-dimer in the three subgroups of different renal function was 3.32, 3.58 and 3.95, respectively. The new D-dimer cut-off value was increased to 1.2 and 1.75 times of the old one in patients with mild and moderate renal impairment and the proportion of patients with a negative D-dimer level raises from 48.7% to 53.0% compare with old D-dimer cut-off value. The sensitivity and specificity of negative D-dimer to rule out PE was 98% and 62% with the new cut-off value versus 99% and 57% with the old cut-off value and the NNT of D-dimer to rule out PE reduced from 3.52 to 3.34.