Glomerular filtration rate estimated by cystatin C among different clinical presentations

Abstract

Glomerular filtration rate (GFR) estimates from serum creatinine has not been generalizable across all populations. Cystatin C has been proposed as an alternative marker for estimating GFR. The objective of this study was to compare cystatin C with serum creatinine for estimating GFR among different clinical presentations. Cystatin C and serum creatinine levels were obtained from adult patients (n=460) during an evaluation that included a GFR measurement by iothalamate clearance. Medical records were abstracted for clinical presentation (healthy, native chronic kidney disease or transplant recipient) at the time of GFR measurement. GFR was modeled using the following variables: cystatin C (or serum creatinine), age, gender and clinical presentation. The relationship between cystatin C and GFR differed across clinical presentations. At the same cystatin C level, GFR was 19% higher in transplant recipients than in patients with native kidney disease (P<0.001). The association between cystatin C and GFR was stronger among native kidney disease patients than in healthy persons (P<0.001 for statistical interaction). Thus, a cystatin C equation was derived using only patients with native kidney disease (n=204). The correlation with GFR (r(2)=0.853) was slightly higher than a serum creatinine equation using the same sample (r(2)=0.827), the Modification of Diet in Renal Disease equation (r(2)=0.825) or the Cockcroft-Gault equation (r(2)=0.796). Averaged estimates between cystatin C and serum creatinine equations further improved correlation (r(2)=0.891). Cystatin C should not be interpreted as purely a marker of GFR. Other factors, possibly inflammation or immunosuppression therapy, affect cystatin C levels. While recognizing this limitation, cystatin C may improve GFR estimates in chronic kidney disease patients.

Monitoring renal function: measured and estimated glomerular filtration rates - a review

“…Both MDRD and C-G equations have been reported to be less accurate in populations without chronic kidney disease, such as young patients with type 1 diabetes without microalbuminuria and potential kidney donors (27,28). Some studies report the higher accuracy of the MDRD equation (26) while others report similar performance of MDRD and C-G equations (29).…”

“…The vast majority, when comparing bias, precision, accuracy, and correlation, found CysC-based equations to be superior to creatinine-based equations as estimates of GFR (45,52,53), while some reported no difference in the performance of CysC-and creatinine-based equations (29,54). Recently, in order to improve the estimated kidney function, estimated GFR equations were developed, which incorporate both SCr and CysC.…”

“…In contrast to the MDRD equation, which was calculated from a large population in a multicenter study, CysC-based equations were created and validated in smaller samples using different gold standard measurements for GFR. Table 3 highlights some CysCbased equations for adults (29,45,(51)(52)(53)(54)(55)(56).…”

Controle da hiperfosfatemia na DRC

“…Against the expectation of being a proper marker, in this group, formulas based on cystatin C overestimate GFR in individuals with higher body mass index (BMI). 46 It is important to emphasize that some formulas have been developed in the past few years with the objective to better evaluate renal function with cystatin C, just as with serum creatinine, to estimate GFR, 20,22,27,[47][48][49][50][51] as demonstrated in Table 2.…”

“…7,15,22,24,25 Such aspects have introduced the idea that serum cystatin C levels are better GFR markers than creatinine, fact that has been confirmed by different studies. 3,5,[8][9][10]15,18,[26][27][28][29] On the other hand, some of them do not show a significant difference between blood determination of cystatin C and creatinine for such purpose. 5,30,31 In the pediatric population, cystatin C has an advantage over serum creatinine, mainly to detect small and early changes in GFR, once this population has reduced muscle mass, especially children under the age of 4 years, that have particularly low serum creatinine values.…”