In malnourished adolescent with anorexia nervosa, Cockroft-Gault formula is the most relevant formula to estimate renal function

Summary Aim Serum creatinine level is the most used test to evaluate renal function in patients with anorexia nervosa (AN). We investigated which formula of glomerular filtration rate (GFR) based on simple blood sample had the best correlation with the gold standard in malnourished adolescent patients with AN. Methods A prospective study was conducted on 34 adolescents hospitalized for the restrictive type of AN between 2014 and 2017. The GFR was measured by isotopic technique and calculated using the Cockroft–Gault, Schwartz equations and 3 other formula. Results For the 34 AN patients, mean BMI -2.7 zscore, the mean measured GFR was 107 +/- 26 mL/min/1.73 m2. Among them, 35% (12/34) had a GFR under 90 mL/min/1.73m2. The calculated GFR with Cockroft–Gault formula had the best correlation with the measured GFR (R2=0.852), whatever the creatinine level. No correlation was found between creatinine level and measured GFR. Conclusion Kidney dysfunction is common in malnourished AN adolescents, so clinicians should always evaluate AN patients for renal impairments. Creatinine level is a poor indicator of renal function in this population. The most accurate formula to test GFR with a simple blood test is the Cockroft-Gault formula.