Pre-chronic kidney disease: Serial creatinine tracks glomerular filtration rate decline above 60 mL/min

OBJECTIVES To allow primary clinicians to detect early decline in glomerular filtration rate, above 60 milliliters per minute, before stage-three chronic kidney disease. RESULTS Four patient cases show how serum creatinine referenced to an individual’s historical maximum can suggest increased risk, triggering investigation to separate benign processes that alter serum creatinine from true decline in glomerular filtration rate of prechronic kidney disease. DISCUSSION/CONCLUSIONS At glomerular filtration rates above 60 milliliters per minute, serial creatinine is more reliable than estimating equations and appears practical for clinical monitoring and early intervention. METHODS We re-examined a standard reference that found low tubular secretion of creatinine at glomerular filtration rates above 80 milliliters per minute and suggested “observation of subtle changes in serum creatinine levels”. We used statistics to explain why that method extends to the 80 to 60 milliliters per minute range: We expanded the y-axis (to reflect accuracy of modern creatinine assays), fitted a hyperbolic curve, and showed reasonable continuity down to 60 milliliters per minute. We summarized why equations estimating glomerular filtration rate are unsuitable above 60 milliliters per minute.