The C hronic K idney D isease E pidemiology C ollaboration cystatin C ( CKD ‐ EPI ‐ C ys C ) equation has an independent prognostic value for overall survival in newly diagnosed patients with symptomatic multiple myeloma; is it time to change from MDRD to CKD ‐ EPI ‐ C ys C equations?

Objectives The estimation of glomerular filtration rate (e GFR ) in multiple myeloma ( MM ) is based on equations that use serum creatinine (s C r), such as the M odification of D iet in R enal D isease ( MDRD ) equation. However, the C hronic K idney D isease E pidemiology C ollaboration ( CKD ‐ EPI ) group has suggested that e GFR based on both s C r and cystatin C ( CKD ‐ EPI ‐s C r‐ C ys C ) is more accurate than other formulae for the estimation of kidney dysfunction. The aim of this study was to prospectively evaluate, for the first time in the literature, the CKD ‐ EPI ‐s CR ‐ C ys C formula in newly diagnosed patients with symptomatic MM . Methods We studied 220 newly diagnosed, previously untreated, patients with symptomatic myeloma and calculated e GFR using the MDRD , the CKD ‐ EPI ‐s CR , the CKD ‐ EPI ‐ C ys C , and the CKD ‐ EPI ‐s C r‐ C ys C equations. Results CKD ‐ EPI ‐s C r‐ C ys C equation detected more myeloma patients with stage 3–5 renal impairment than the MDRD , CKD ‐ EPI , or CKD ‐ EPI ‐ C ys C equations: 45% vs. 39.5%, 42.2%, and 43.1%, respectively ( P  < 0.01). This was also observed in the elderly patients (>70 yrs), while in patients ≤70 yrs, the CKD ‐ EPI ‐ C ys C equation managed to identify higher number of patients with stage 3–5 renal impairment ( RI ) than the other equations. Furthermore, 63 (28.6%) patients with e GFR values by the MDRD formula were reclassified to higher CKD stages according to CKD ‐ EPI ‐ C ys C equation. The median overall survival for all patients was 52 months. In the multivariate analysis, that included International Staging System stage, lactate dehydrogenase ( LDH ) ≥300 U/L and e GFR for each different equation (as a continuous variable), only e GFR that included C ys C , but not s C r had independent prognostic value ( P  = 0.013) along with high LDH ( P  = 0.029). Conclusions Our results suggest that equations based on C ys C reveal higher number of MM patients with RI compared with equations based only in s C r. Furthermore, the CKD ‐ EPI ‐ C ys C formula independently predicted for survival. Based on these data, we suggest that CKD ‐ EPI equations based on C ys C should substitute MDRD , as it has been suggested for patients with several other renal disorders.