The online version of this article (https://doi.org/10.1186/s12882-018-0813-9) contains supplementary material, which is available to authorized users.
Accurate estimation of glomerular filtration rate (GFR) is important for diagnosis and risk stratification in chronic kidney disease and for selection of living donors. Ethnic differences have required correction factors in the originally developed creatinine-based GFR estimation equations for populations around the world. Existing equations have not been validated in the vegetarian Indian population. We examined the performance of creatinine and cystatin-based GFR estimating equations in Indians.
GFR was measured by urinary clearance of inulin. Serum creatinine was measured using IDMS-traceable Jaffe’s and enzymatic assays, and cystatin C by colloidal gold immunoassay. Dietary protein intake was calculated by measuring urinary nitrogen appearance. Bias, precision and accuracy were calculated for the eGFR equations.
A total of 130 participants (63 healthy kidney donors and 67 with CKD) were studied. About 50% were vegetarians, and the remainder ate meat 3.8 times every month. The average creatinine excretion were 14.7 mg/kg/day (95% CI: 13.5 to 15.9 mg/kg/day) and 12.4 mg/kg/day (95% CI: 11.2 to 13.6 mg/kg/day) in males and females, respectively. The average daily protein intake was 46.1 g/day (95% CI: 43.2 to 48.8 g/day). The mean mGFR in the study population was 51.66 ± 31.68 ml/min/1.73m2. All creatinine-based eGFR equations overestimated GFR (p < 0.01 for each creatinine based eGFR equation). However, eGFR by CKD-EPICys was not significantly different from mGFR (p = 0.38). The CKD-EPICys exhibited lowest bias [mean bias: −3.53 ± 14.70 ml/min/1.73m2 (95% CI: -0.608 to −0.98)] and highest accuracy (P30: 74.6%). The GFR in the healthy population was 79.44 ± 20.19 (range: 41.90–134.50) ml/min/1.73m2.
Existing creatinine-based GFR estimating equations overestimate GFR in Indians. An appropriately powered study is needed to develop either a correction factor or a new equation for accurate assessment of kidney function in the Indian population.
Additional file 1: Table S1. Estimating GFR equations. Table S2. Characteristics and measurements in study population (stratified by mGFR groups). Table S3. Performance of GFR estimating equations as compared to measured GFR by urinary inulin clearance (stratified by mGFR groups). Table S4. GFR measurements in study population (stratified by age). Table S5. Performance of GFR estimating equations as compared to measured GFR by urinary inulin clearance (stratified by age). Table S6. Performance of GFR estimating equations (eGFR calculated using serum creatinine values by modified Jaffe method) as compared to measured GFR by urinary inulin clearance. (DOCX 76 kb)12882_2018_813_MOESM1_ESM.docx
Additional file 2: Figure S1. A. Correlation between serum creatinine (mg/dL) measured by modified Jaffe’s method and enzymatic method (Pearson correlation coefficient, r = 0.965, p < 0.0001); B. Bland Altman analysis of difference between serum creatinine values (in mg/dL) measured by enzymatic and modified Jaffe’s methods (X-axis represents difference between two values and Y-axis represents mean of two values, red line represents mean difference and green line represents 95% limits of agreement. (DOCX 1387 kb)12882_2018_813_MOESM2_ESM.docx
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- Existing creatinine-based equations overestimate glomerular filtration rate in Indians
Ashok Kumar Yadav
Krishan L. Gupta
Harbir Singh Kohli
- BioMed Central
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