CST3 and obesity due to melanocortin 4 receptor deficiency: Similarly, CKD-EPI (creatinine-cystatin C) uses serum creatinine, cystatin C, sex, and age of the patient.33 Nonetheless, in our study, CKD-EPI (creatinine-cystatin C) provided an underestimation of carboplatin exposure dependent on BMI, ranging from +0.4% for patients with a normal weight to −7.0% for those who were overweight and −17.8% for those who had obesity.