Estimation of Glomerular Filtration Rate Based on the Modification of Diet in Renal Disease Equation in Patients with Chronic Renal Failure

Abstract

The list of indications for initiating regular dialysis treatment includes residual glomerular filtration rate (GFR). Under the current European Best Practice Guidelines for Hemodialysis, residual GFR (and the presence of one or more symptoms of uremia) should not decrease below 15 ml/min. The present article seeks to determine to what extent the modification of diet in renal disease (MDRD) equation enables the detection of this decrease in GFR. We tried to answer this question using a more detailed analysis of the relationship between MDRD and renal inulin clearance (C_in). Residual GFR based on C_in (under conditions of stable plasma levels and water loading) and GFR calculated using the MDRD equation was measured in 79 individuals with chronic renal failure (with mean C_in = 19.1 ± 10.1 ml/min/1.73 m²). Statistical evaluation was performed using regression analysis, the interchangeability of both methods (Bland-Altman) and receiver-operating characteristic (ROC) curve analysis. Regression analysis demonstrated a significant correlation between MDRD and C_in (r = 0.892; p < 0.001). However, the regression equation line for the correlation differs significantly from the identity line (p < 0.001). The value of the regression coefficient (0.722) is significantly lower than 1.0 (CI₅₀ 0.63; 0.81). The mean MDRD – C_in difference was 3.26 ± 4.46 ml/min/1.73 m² and the value was significantly different from zero (p < 0.001). The mean difference +2 SD was 12.2 ml/min/1.73 m², and the mean – 2 SD was –5.7 ml/min/1.73 m². ROC curve analysis (for a cutoff C_in = 15 ml/min/1.73 m²) indicates an area under the curve (AUC) of 0.954 ± 0.023. The best combination of sensitivity and specificity was obtained for a MDRD of 19.7 ml/min/1.73 m², with a sensitivity of 90.5% and specificity of 87.5%. For cutoff value of C_in = 10 ml/min/1.73 m², the AUC was 0.939 ± 0.026 (CI₉₅ 0.863–0.890). A combination of maximum sensitivity and specificity was obtained with an MDRD of 16.5 ml/min/1.73 m². With this value, MDRD sensitivity was 100% and specificity 81.5%. A significant correlation between the MDRD equation and the measured creatinine clearance (C_cr) was found (r = 0.883, p < 0.001). The mean difference of MDRD – C_cr was –7.2 ± 6.5 ml/min/1.73 m². This is significantly different from that of MDRD – C_in (p < 0.001). Our results suggest that MDRD and C_in in individuals with chronic renal failure are not interchangeable methods for a GFR <15 ml/min/1.73 m² determination. However, MDRD may furnish valuable information in terms of detecting a critical decrease in GFR; but, the MDRD equation for this decrease in GFR (15 ml/min/1.73 m²) will provide a somewhat higher value (19.7 ml/min/1.73 m²).

Renal function assessment in patients with systemic lupus erythematosus

“…Among the diVerent studies, the MDRD study equation had less bias, better precision, and accuracy in GFR estimates than CG equation, mainly in patients with low GFR [21][22][23]. The MDRD equation produced reliable information when compared with inulin clearance in patients with chronic renal failure [24], but with this equation, GFR estimates are less precise at higher GFR as our study (Fig. 2) and others described [4,6].…”

Individualizing Pharmacotherapy in Patients with Renal Impairment: The Validity of the Modification of Diet in Renal Disease Formula in Specific Patient Populations with a Glomerular Filtration Rate below 60 Ml/Min. A Systematic Review

“…In Table 2 three studies are presented, which fulfilled our inclusion criteria. All three studies reported an overestimation of the true GFR, ranging from a mean bias of 3.26 ml/min/1.73m 2 in the study of Schuck et al to a median relative bias of 53% in the study of Poggio et al[ 85 , 86 ] In the study of Poggio et al the MDRD-6 formula seemed to perform slightly better than the MDRD-4 formula with a median bias of 46%. [ 85 ] Although the bias in the study of Schuck et al seems low, the precision exceeded our criteria of 30%.…”

“…[ 85 ] Although the bias in the study of Schuck et al seems low, the precision exceeded our criteria of 30%. [ 86 ] Only the study of Poggio et al reported accuracy, which appeared to be inadequate. P 30 was 36% for the MDRD-6 formula and 31% for the MDRD-4 formula.…”

“…[ 85 ] The measurement of the GFR with a gold standard was performed reasonably, although the spontaneous urination instead of catheterization in the study of Schuck et al is questionable. [ 86 ] The number of patients only exceeded 100 in the study of Poggio et al[ 85 ]…”

How do laboratory specialists advise clinicians concerning the use and interpretation of renal tests?

“…They are easy to obtain and more accurate than some of the more cumbersome methods (e.g. creatinine clearance)(84)(85)(86). This makes the screening of large populations possible, and it has been shown that reporting eGFR values facilitates the early diagnosis of renal disease(87)(88)(89) and can be used for drug dosing(90).…”