Cystatin C measurement leads to lower metformin dosage in elderly type 2 diabetic patients

Abstract

The aim of this study was to provide evidence for the hypothesis that estimated glomerular filtration rate from serum Cystatin C (eGFRcys) is better to be determined for all elderly type 2 diabetes mellitus (T2DM) patients based on eGFRcys upward and downward reclassification rate for hypothetical metformin dose reduction by eGFRcys at the GFR decision point of 45 mL/min/1.73 m . A total of 265 consecutive T2DM elderly patients (age range 65-91 years) from outpatient diabetic clinic were included in the study. The Kidney Disease Improving Global Outcomes (KDIGO) guidelines for metformin dosing were strictly followed. Estimated glomerular filtration rate from serum creatinine (eGFRcrea) led to results of metformin eligibility. Each of the results of eGFRcrea-based eligibility was further compared to eGFRcys-based eligibility. Creatinine was measured by enzymatic method standardized against international reference material SRM 967. Cystatin C was determined by method traceable to DA ERM 471 international standard. eGFRcrea and eGFRcys were calculated according to Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations. A downward reclassification rate was higher than upward reclassification rate (31 vs 3, respectively; P < 0.0001). The median (IQR) eGFRcrea was higher than eGFRcys (73 (58-85) vs 63 (50-75) mL/min/1.73 m , respectively; P < 0.0001). eGFRcys reclassified significant proportion of patients with T2DM from metformin eligible CKD stages to less or non-eligible stages. The downward reclassification was more frequent in patients older than 80 years (P < 0.01). Cystatin C-based eGFR selects more complicated patients, where lower doses of metformin are possibly advisable. We recommend calculating both eGFRcrea and eGFRcys for metformin dosing in elderly patients with T2DM.

Estimated GFR With Cystatin C and Creatinine in Clinical Practice: A Retrospective Cohort Study

“…Our study highlights that the use of cystatin C eGFR across settings will result in differences in CKD staging compared with creatinine eGFR measurements, which may meaningfully affect clinical decision making. For example, of the 564 patients diagnosed with stage 3 CKD using creatinine, 34% were changed to a later stage CKD (stage 4 or 5) using cystatin C, which could result in nephrology referral (recommended for an eGFR < 30 mL/min/1.73 m 2 ), 21 medication adjustments, 22 earlier discussion regarding kidney replacement modalities, and kidney transplant evaluation referral. 23 CKD stage changes are more likely among patients who are older and have a greater comorbidity burden, representing a group of patients who are at a higher risk for adverse outcomes, whereas the severity of their kidney disease may be underappreciated.…”

Effects of different doses of metformin on bone mineral density and bone metabolism in elderly male patients with type 2 diabetes mellitus

“…Furthermore, a large amount of calcium and phosphate ions in serum is excreted out of the body by osmotic diuretics. In that, the decreased blood calcium and phosphate concentrations may lead to osteocyte dysfunction[ 9 , 10 ]. Second, the poor blood glucose control may cause accumulation of glycosyl compound that may further promote oxidative stress and then lead to osteopenia and myelosuppression.…”