Estimated glomerular filtration rates cannot replace measured GFR in type 1 diabetes patients with hyperfiltration

Aim This study of children and young adults with type 1 diabetes with normal to high glomerular filtration rates (GFR) compared estimated GFR (eGFR) with measured GFR (mGFR). Methods GFR was measured by inulin clearance, and we carried out simultaneous analyses of standardised creatinine and cystatin C. eGFR was calculated using different formulas. Results We enrolled 106 patients, including 56 males, aged 21.9 (standard deviation 9.2) years with 13.7 (9.1) years' duration of diabetes and a mean haemoglobin A1c (HbA1c) of 7.7% (61 mmol/mol). The median mGFR was 128 (111–143) mL/min/1.73 m2. Most of the eGFR estimations failed to detect a significant proportion of hyperfiltration based on inulin clearance. The best accuracy (P30) between eGFR and mGFR was seen with eGFRCKD-EPI (92%), eGFRcys C Berg (86%), eGFRcys C CAPA (78%) and eGFRcys C Inker (84%) where eGFRCKD-EPI and eGFR cys C Berg showed the lowest bias. Most eGFRcys C measurements showed greater accuracy when combined with eGFRcr (P30 92–94%). Conclusion The best accuracy (P30) and lowest bias were found with eGFRCKD-EPI and eGFR Berg. in this cohort. However, eGFR cannot accurately replace mGFR to detect hyperfiltration and follow GFR over time in young patients with type 1 diabetes.