In addition to urinary ACR, glomerular filtration rate (GFR) is a useful marker of kidney function. The ISPAD and ADA guidelines also recommend including estimated GFR (eGFR) in DKD screening for children and young people with diabetes, although with the limitation of a lack of validated formula to calculate this in youth with T1D. A simplified version of the Chronic Kidney Disease in Children (CKiD) equation, also known as the updated Schwartz formula,11 is commonly used for eGFR calculation in children (Box 2). A recent study comparing methods to estimate GFR in young people with T1D suggested that a sex-adjusted version of the CKiD equation, CKiD1 (Box 2), was more accurate, although this study included no young people aged <17 years and very few with eGFR <90 mL/min/1.73 m2.11 Another study focusing on children with T2D developed and validated the iCARE equation (Box 2) to estimate GFR, although again the prevalence of eGFR <90 mL/min/1.73 m2 in the study was very low, and the equation has not yet been validated in young people with T1D.12

Recommended target4: eGFR >90 mL/min/1.73 m2

CKiD equation11: eGFR=36.5×height/sCr

Sex-dependent CKiD1 equation11: eGFR=k×height/sCr, where k=37.0 for males and 33.2 for females

iCARE equation12: eGFR=50.7 BSA0.816×(height/sCr)0.405×q, where q=1 for males and 0.8994 for females

BSA, body surface area in m2 calculated using the Haycock formula (BSA=weight0.5378×height0.3964×0.024265); CKiD, Chronic Kidney Disease in Children; CKiD1, sex-adjusted version of CKiD; eGFR, estimated glomerular filtration rate in mL/min/1.73 m2, height in cm; sCr, serum creatinine in μmol/L, weight in kg.

For our young person, eGFR using the CKiD1 equation, based on his age, sex, height and serum creatinine level, was 127 mL/min/1.73 m2 (normal).