Differences in the glomerular filtration rate calculated by two creatinine-based and three cystatin-C-based formulae...

Reduced renal function is a health problem in elderly patients. Different creatinine- and cystatin-C-based formulae have been used to estimate glomerular filtration rate (GFR).

To investigate individual and group differences of GFR estimates derived from five different formulae.

60 patients were randomly assigned to participate in this cross-sectional study. Nutrition status was assessed, blood samples were drawn and GFR was calculated using two creatinine- and three cystatin-C-based formulae.

Four of five formulae indicate reduced GFR in >70% of the participants, GFR was significantly less in malnourished patients according to one creatinine formula. Estimates from the formulae were highly correlated (r = 0.607-0.863, p < 0.001), but individual differences were between -36.1 and 79.9 ml/min/1.73 m(2). The formulae grouped 38.3-60.0% of the subjects differently into the five stages of chronic kidney disease. BMI, total cholesterol, age and gender were significant predictors for the calculated GFR differences between the formulae.

The prevalence of reduced renal function is high in elderly hospitalized patients. BMI, age and/or gender can affect GFR estimates depending on the formula used, and there is an association between total cholesterol and calculated GFR differences between formulae. Different formulae can result in a different grouping of patients into the five stages of chronic renal disease.