Adiposity is associated with cystatin C. Cystatin C-based glomerular filtration rate (GFR) equations may result in the over-estimation of chronic kidney disease (CKD) prevalence at higher body mass index (BMI) levels.
Setting and Participants
6,709 US adult NHANES III participants.
Body mass index
Absolute percent difference in the prevalence of stage 3 or 4 CKD between creatinine- and cystatin C-based estimating equations by level of BMI.
Normal weight, overweight, and obesity were defined as BMI levels of 18.5 to <25.0, 25 to <30.0, and ≥30 kg/m2, respectively. Stage 3 or 4 CKD (eGFR of 15 to 59 ml/min/1.73m2) was defined using the abbreviated creatinine-based Modification of Diet in Renal Disease equation (eGFRMDRD); a cystatin C, age, sex, and race equation (eGFRCysC,age,sex,race); a cystatin C only equation (eGFRCysC); cystatin C≥1.12 mg/L (elevated cystatin C); and an equation incorporating serum creatinine, cystatin C, age, sex, and race (eGFRCr,CysC,age,sex,race).
The differences in stage 3 or 4 CKD prevalence between eGFRCysC,age,sex,race, eGFRCysC, and elevated cystatin C, separately, and eGFRMDRD were larger at higher BMI levels. Specifically, compared to estimates derived using eGFRMDRD, for normal weight, overweight, and obese participants, the prevalence of stage 3 or 4 CKD was 2.1%, 3.0%, and 6.5% higher, respectively, when estimated by eGFRCysC,age,sex,race (p-trend=0.005); 0.1%, 0.6%, 2.2% higher, respectively, for eGFRCysC (p-trend=0.028); 2.9%, 5.2%, and 9.5% higher, respectively, for elevated cystatin C (p-trend<0.001); and −0.1%, −0.4%, and 0.0% higher, respectively, for eGFRCr,CysC,age,sex,race (p-trend=0.719).
No gold standard measure of GFR was available.
BMI may influence the prevalence of stage 3 or 4 CKD when cystatin C-based equations are used.