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Open Access Original investigation

Distribution of cardiovascular disease and retinopathy in patients with type 2 diabetes according to different classification systems for chronic kidney disease: a cross-sectional analysis of the renal insufficiency and cardiovascular events (RIACE) Italian multicenter study

Giuseppe Pugliese1*, Anna Solini2, Enzo Bonora3, Emanuela Orsi4, Gianpaolo Zerbini5, Cecilia Fondelli6, Gabriella Gruden7, Franco Cavalot8, Olga Lamacchia9, Roberto Trevisan10, Monica Vedovato11, Giuseppe Penno2 and for the RIACE Study Group

Author Affiliations

1 Department of Clinical and Molecular Medicine, “La Sapienza” University, Via di Grottarossa, 1035-1039, 00189 Rome, Italy

2 Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy

3 Division of Endocrinology and Metabolic Diseases, University of Verona, Verona, Italy

4 Endocrinology and Diabetes Unit, Department of Medical Sciences, Fondazione IRCCS “Cà Granda – Ospedale Maggiore Policlinico”, Milan, Italy

5 Complications of Diabetes Unit, Division of Metabolic and Cardiovascular Sciences, San Raffaele Scientific Institute, Milan, Italy

6 Diabetes Unit, Department of Internal Medicine, Endocrine and Metabolic Sciences and Biochemistry, University of Siena, Siena, Italy

7 Department of Internal Medicine, University of Turin, Turin, Italy

8 Unit of Internal Medicine, Department of Clinical and Biological Sciences, University of Turin, Turin, Orbassano, Italy

9 Unit of Endocrinology and Metabolic Diseases, Department of Medical Sciences, University of Foggia, Foggia, Italy

10 Diabetes Unit, Hospital of Bergamo, Bergamo, Italy

11 Department of Clinical and Experimental Medicine, University of Padua, Padua, Italy

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Cardiovascular Diabetology 2014, 13:59  doi:10.1186/1475-2840-13-59

Published: 13 March 2014

Abstract

Background

The National Kidney Foundation’s Kidney Disease Outcomes Quality Initiative (NKF’s KDOQI) staging system for chronic kidney disease (CKD) is based primarily on estimated GFR (eGFR). This study aimed at assessing whether reclassification of subjects with type 2 diabetes using two recent classifications based on both eGFR and albuminuria, the Alberta Kidney Disease Network (AKDN) and the Kidney Disease: Improving Global Outcomes (KDIGO), provides a better definition of burden from cardiovascular disease (CVD) and diabetic retinopathy (DR) than the NKF’s KDOQI classification.

Methods

This is a cross-sectional analysis of patients with type 2 diabetes (n = 15,773) from the Renal Insufficiency And Cardiovascular Events Italian Multicenter Study, consecutively visiting 19 Diabetes Clinics throughout Italy in years 2007-2008. Exclusion criteria were dialysis or renal transplantation. CKD was defined based on eGFR, as calculated from serum creatinine by the simplified Modification of Diet in Renal Disease Study equation, and albuminuria, as measured by immunonephelometry or immunoturbidimetry. DR was assessed by dilated fundoscopy. Prevalent CVD, total and by vascular bed, was assessed from medical history by recording previous documented major acute events.

Results

Though prevalence of complications increased with increasing CKD severity with all three classifications, it differed significantly between NKF’s KDOQI stages and AKDN or KDIGO risk categories. The AKDN and KDIGO systems resulted in appropriate reclassification of uncomplicated patients in the lowest risk categories and a more graded independent association with CVD and DR than the NKF’s KDOQI classification. However, CVD, but not DR prevalence was higher in the lowest risk categories of the new classifications than in the lowest stages of the NKF’s KDOQI, due to the inclusion of subjects with reduced eGFR without albuminuria. CVD prevalence differed also among eGFR and albuminuria categories grouped into AKDN and KDIGO risk category 1 and moderate, respectively, and to a lesser extent into higher risk categories.

Conclusions

Though the new systems perform better than the NKF’s KDOQI in grading complications and identifying diabetic subjects without complications, they might underestimate CVD burden in patients assigned to lower risk categories and should be tested in large prospective studies.

Trial registration

ClinicalTrials.gov; NCT00715481

Keywords:
Chronic kidney disease; Classification; eGFR; Albuminuria; Cardiovascular disease; Diabetic retinopathy