Are prediction equations for glomerular filtration rate useful for the long-term monitoring of type 2 diabetic patients?

Nephrol Dial Transplant. 2006 Aug;21(8):2152-8. doi: 10.1093/ndt/gfl221. Epub 2006 May 15.

Abstract

Background: The aim of this study was to compare the accuracy of prediction equations [modification of diet in renal disease (MDRD), simplified MDRD, Cockcroft-Gault (CG), reciprocal of creatinine and creatinine clearance] in a cohort of patients with type 2 diabetes.

Methods: A total of 525 glomerular filtration rates (GFRs) using (125)I-iothalamate were carried out over 10 years in 87 type 2 diabetic patients. Accuracy was evaluated at three levels of renal function according to the baseline values obtained with the isotopic method: hyperfiltration (GFR: >140 ml/min/1.73 m(2); 140 isotopic determinations in 27 patients), normal renal function (GFR: 140-90 ml/min/1.73 m(2); 294 isotopic determinations in 47 patients) and chronic kidney disease (CKD) stages 2-3 (GFR: 30-89 ml/min/1.73 m(2); 87 isotopic determinations in 13 patients). The annual slope for GFR (change in GFR expressed as ml/min/year) was considered to ascertain the variability in the equations compared with the isotopic method during follow-up. Student's t-test was used to determine the existence of significant differences between prediction equations and the isotopic method (P < 0.05 with Bonferroni adjusted for five contrast tests).

Results: In the subgroup of patients with hyperfiltration, a GFR slope calculated with (125)I-iothalamate -4.8 +/- 4.7 ml/min/year was obtained. GFR slope in patients with normal renal function was -3.0 +/- 2.3 ml/min/year. In both situations, all equations presented a significant underestimation compared with the isotopic GFR (P < 0.01; P < 0.05). In the subgroup of CKD stages 2-3, the slope for GFR with (125)I-iothalamate was -1.4 +/- 1.8 ml/min/year. The best prediction equation compared with the isotopic method proved to be MDRD with a slope for GFR of -1.4 +/- 1.3 ml/min/year (P: NS) compared with the CG formula -1.0 +/- 0.9 ml/min/year (P: NS). Creatinine clearance presented the greatest variability in estimation (P < 0.001).

Conclusions: In the normal renal function and hyperfiltration groups, none of the prediction equations demonstrated acceptable accuracy owing to excessive underestimation of renal function. In CKD stages 2-3, with mean serum creatinine > or =133 micromol/l (1.5 mg/dl), the MDRD equation can be used to estimate GFR during the monitoring and follow-up of patients with type 2 diabetes receiving insulin, anti-diabetic drugs or both.

Publication types

  • Evaluation Study

MeSH terms

  • Adult
  • Aged
  • Ambulatory Care
  • Chronic Disease
  • Cohort Studies
  • Creatinine / blood
  • Diabetes Mellitus, Type 2 / drug therapy
  • Diabetes Mellitus, Type 2 / metabolism*
  • Diabetic Nephropathies / diagnosis
  • Diabetic Nephropathies / metabolism
  • False Positive Reactions
  • Female
  • Follow-Up Studies
  • Glomerular Filtration Rate*
  • Humans
  • Hypoglycemic Agents / therapeutic use
  • Insulin / therapeutic use
  • Iodine Radioisotopes / pharmacokinetics
  • Iothalamic Acid / pharmacokinetics
  • Kidney Diseases / complications
  • Kidney Diseases / metabolism
  • Male
  • Mathematics
  • Middle Aged
  • Predictive Value of Tests
  • Reproducibility of Results
  • Severity of Illness Index

Substances

  • Hypoglycemic Agents
  • Insulin
  • Iodine Radioisotopes
  • Iothalamic Acid
  • Creatinine