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Open Access Research article

The glomerular filtration rate estimated by new and old equations as a predictor of important outcomes in elderly patients

Gijs Van Pottelbergh12*, Bert Vaes12, Wim Adriaensen12, Cathy Matheï12, Delphine Legrand2, Pierre Wallemacq3 and Jean Marie Degryse12

Author Affiliations

1 Department of Public Health and Primary Care, Katholieke Universiteit Leuven, Kapucijnenvoer 33, blok J, PB 7001 3000, Leuven, Belgium

2 Institute of Health and Society, Université Catholique de Louvain, Brussels, Belgium

3 Laboratory of Analytical Biochemistry, Cliniques Universitaires St Luc, Université Catholique de Louvain, Brussels, Belgium

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BMC Medicine 2014, 12:27  doi:10.1186/1741-7015-12-27

Published: 12 February 2014

Abstract

Background

The prevalence of chronic kidney disease (CKD) increases with age, and new glomerular filtration rate-estimating equations have recently been validated. The epidemiology of CKD in older individuals and the relationship between a low estimated glomerular filtration rate as calculated by these equations and adverse outcomes remains unknown.

Methods

Data from the BELFRAIL study, a prospective, population-based cohort study of 539 individuals aged 80 years and older, were used. For every participant, five equations were used to calculate estimated glomerular filtration rate based on serum creatinine and/or cystatin C values: MDRD, CKD-EPIcreat, CKD-EPIcyst, CKD-EPIcreatcyst, and BIS equations. The outcomes analyzed included mortality combined with the necessity of new renal replacement therapy, severe cardiovascular events, and hospitalization.

Results

During the follow-up period, which was an average of 2.9 years, 124 participants died, 7 required renal replacement therapy, 271 were hospitalized, and 73 had a severe cardiovascular event. The prevalence of estimated glomerular filtration rate values <60 mL/min/1.73 m2 differed depending on the equation used as follows: 44% (MDRD), 45% (CKD-EPIcreat), 75% (CKD-EPIcyst), 65% (CKD-EPIcreatcyst), and 80% (BIS). All of the glomerular filtration rate-estimating equations revealed that higher cardiovascular mortality was associated with lower estimated glomerular filtration rates and that higher probabilities of hospitalization were associated with estimated glomerular filtration rates <30 mL/min/1.73 m2. A lower estimated glomerular filtration rate did not predict a higher probability of severe cardiovascular events, except when using the CKD-EPIcyst equation. By calculating the net reclassification improvement, CKD-EPIcyst and CKD-EPIcreatcyst were shown to predict mortality (+25% and +18%) and severe cardiovascular events (+7% and +9%) with the highest accuracy. The BIS equation was less accurate in predicting mortality (-12%).

Conclusion

Higher prevalence of CKD were found using the CKD-EPIcyst, CKD-EPIcreatcyst, and BIS equations compared with the MDRD and CKD-EPIcreat equations. The new CKD-EPIcreatcyst and CKD-EPIcyst equations appear to be better predictors of mortality and severe cardiovascular events.

Keywords:
Cardiovascular events; eGFR; Hospitalizations; Mortality; Renal function