CST3 and chronic kidney disease: In G1 and 2, no significant correlations were obtained with respect to 99mTc-DTPA, but the same pattern of high significance was observed among the different equations, being creatinine CKD EPI-combined CKD EPI the highest correlation obtained in stage 1 (ρ = 0.8522, P < 0.0001) and Hoek-cystatin C CKD EPI in stage 2 (ρ = 0.9496, P < 0.0001) (Tables 6 and 7).