CR1 and nonpapillary renal cell carcinoma: Further, The CR-1 serum levels were determined, and CR-1 concentrations were notably higher in ccRCC patients (n = 38) than in healthy controls (n = 35) (3.34 ± 2.08 ng/mL vs 1.04 ± 0.33 ng/ml, P <  0.001; Fig. 3a).