Which Calculation Method of Glomerular Filtration Rate is Suitable in Patients With Normal or Mildly Impaired Renal Function?

Abstract

We read the article entitled ''Association of Glomerular Filtration Rate With Slow Coronary Flow in Patients With Normal to Mildly Impaired Renal Function'' by Akin et al 1 with interest. The authors 1 concluded that estimated glomerular filtration rate (eGFR) was significantly correlated with slow coronary flow in patients with normal to mildly impaired kidney function.The Kidney Disease: Improving Global Outcomes organization developed clinical practice guidelines 2 in 2012, recommending that the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is used for reporting eGFR, particularly in patients with a GFR 60 mL/min/1.73 m 2 . Compared with the Modification of Diet in Renal Disease (MDRD) equation, the CKD-EPI equation may be more accurate in patients with measured 3 GFR 60 mL/min/1.73m 2 . Additionally, the CKD-EPI study equation more appropriately categorizes individuals at risk of CKD and cardiovascular disease in a middle-aged population with normal or near-normal kidney function. 4 It has been shown in several communitybased cohorts that people who were reclassified to a higher GFR stage using the CKD-EPI study equation compared with the MDRD study equation had lower risk of adverse events. 5,6 Estimated glomerular filtration rate overestimates measured GFR when serum creatinine is rising and underestimates measured GFR when serum creatinine is falling. 7 Altered muscle mass (eg, reduced by amputation, paraplegia, immobilization, or a neuromuscular disorder and increased by dietary protein intake or creatine dietary supplements), some medications (like aminoglycosides or trimethoprim), and dietary intake (eg, vegetarians) can affect the creatinine levels and eGFR. 7 Akin et al 1 did not mention these factors as exclusion criteria.Finally, the National Kidney Disease Education Program recommends calibrating serum creatinine measurement to isotope dilution mass spectrometry. 8 In the ''Laboratory Measurements'' section of the article, Akin et al 1 mention cholesterol, uric acid, and hemoglobin measurements but the most important parameter of this study, creatinine, was not mentioned.In conclusion, in the light of recently published data, it is probably better to use the CKD-EPI equation to calculate eGFR in patients with near-normal or mildly impaired renal function.

Is there a relationship between slow coronary flow and normal to mildly impaired renal function?

“…In addition, it was determined that this equation overcame the limitation of the MDRD equation (i.e., the underestimation of GFR at given range). [17][18][19][20] Stevens LA et al [20] showed that bias was substantially decreased with the CKD-EPI equation, compared to measured GFR, particularly among people with eGFR greater than 60 ml/min/1.73 m 2 . The study also found that bias was increased using the MDRD equation, when eGFR was greater than 90 ml/min/1.73 m 2 .…”

“…According to the Kidney Disease: Improving Global Outcomes (KDIGO) 2012 guideline, the CKD-EPI equation provides less bias than the MDRD equation, as well as improved risk stratification, [16] and recent studies have confirmed these findings. [17][18][19][20] In the present study, eGFR values in patients with normal coronary flow (NCF) and SCF, who had near-normal or mildly impaired renal function were compared using the CKD-EPI and MDRD equations. The present study was the first to evaluate this relationship with the CKD-EPI equation.…”

Association of Glomerular Filtration Rate With Slow Coronary Flow in Patients With Normal to Mildly Impaired Renal Function

“…We thank Cabuk et al 1 for their comments. 2 They raise concerns about the equation used for reporting estimated glomerular filtration rate (eGFR) in our study and how this could impact on our results.…”

“…Cabuk et al 1 wanted to clarify the possible factors that can influence the creatinine levels and eGFR in our study. Patients with altered muscle mass (eg, reduced by amputation, paraplegia, immobilization, or a neuromuscular disorder and increased by dietary protein intake or creatine dietary supplements) were excluded from our study.…”

“…Cabuk et al 1 also wanted to clarify the measurement of creatinine. Creatinine was measured by a qualified technician using enzymatic assays (Roche Products Ltd, Japan) on a fully automatic biochemical autoanalyzer (COBAS c8000; Roche Products Ltd,) with the Jaffe method.…”