Clinical Significance Of Chronic Kidney Disease In The Elderly

Abstract

Background: Chronic kidney disease (CKD) is a common chronic disease which can be very costly to treat if it progresses to end stage renal disease. Screening for chronic renal insufficiency is widely available, yet little is known about which screening estimation formula is most appropriate in the elderly patient. Review: The two most common formulas for estimation of glomerular filtration rate (GFR) are the Cockcroft/Gault, developed in 1976 and the MDRD, developed in 1999. Both are based on demographic variables such as age, gender, and race as well as the laboratory variable of creatinine. The Cockcroft/Gault formula also includes patient weight. Both formulas were developed in middle aged (not elderly) cohorts who were primarily men and Caucasian. Methods & design: This is a secondary data analysis of an existing database collected from retrospective chart review of a convenience sample. eGFR was calculated by both MDRD and Cockcroft/Gault. Characteristics of patients with and without CRI were compared. Characteristics of patients who experienced a rapid decline in GFR over the 2 year study period by the two formulas were also described. Results: 311 patients were included in the analysis. Patients identified with renal insufficiency were 22% of the total sample regardless of the formulas used for estimation. The sample consisted of 75% women who were 65% African American with a mean age of 72 (SD 7). At least 63% of the sample was overweight or obese. The Cockcroft/Gault formula tended to identify patients with less comorbidity than the MDRD where the patients seemed to be more advanced in the course of their disability. Both formulas were related to congestive heart failure, beta blocker use, avoidance of metformin and ARB use, as well as higher creatinine, and BUN levels and lower hemoglobin levels. Latino ethnic identity had a protective effect. When the Cockcroft/Gault formula was calculated with ideal body weight, the resulting eGFR correlated best with MDRD. Summary: Older patients should be screened for renal insufficiency. The Cockcroft/Gault formula using ideal body weight may provide the most conservative and useful estimation of GFR in elderly patients.