GRP and non-small cell lung carcinoma: Conversely, another report showed that plasma ProGRP levels effectively distinguished pulmonary carcinoids from non-small-cell lung cancer or benign disease, with a sensitivity of 60.9% and a specificity of 89.3% [6]. Furthermore, because the plasma ProGRP level correlates with the Ki-67 index and the number of dividing cells in pulmonary carcinoids [7], higher levels may indicate more advanced cases.