Date of Award
Background: The Cockcroft and Gault equation is widely accepted in practice as the most appropriate way to calculate an estimated creatinine clearance. Geriatric patients often present with reduced muscle mass, and therefore lower creatinine production, due to normal changes in body composition associated with aging. Because serum creatinine and creatinine clearance are inversely proportional using the Cockcroft and Gault equation, a lower serum creatinine may falsely overestimate renal function in the elderly population. Rounding to a normal serum creatinine is believed by some practitioners to prevent over estimation of creatinine clearance and renal function.
Objective: The objective of this study is to identify and compare medications that require renal dose adjustment when using the patient's measured serum creatinine, if less than 1 mg/dL, versus a rounded serum creatinine of 1 mg/dL in the Cockcroft and Gault equation.
Methods: Each patient's estimated creatinine clearance was calculated using the patient's measured serum creatinine and a rounded value of 1 mg/dl, in the Cockcroft and Gault equation. Once both creatinine clearances had been calculated, an evaluation was completed to determine how many of the patient's medications required renal dose adjustment based on either the measured or rounded creatinine clearance. The number of dosing discrepancies was then assessed, in addition to creatinine clearance values, to look for trends or patterns regarding the amount of dosing discrepancies and the effects of rounding to a serum creatinine of 1 mg/dL.
Results: A total of 32 patients (6 male, 26 female) were evaluated for renal dose adjustments based on the measured and rounded creatinine clearance. Seven patients were identified as having discrepancies, all of which were female patients. The average difference between the measured and rounded creatinine clearance in female patients was 16 mL/min. A total of 12 discrepancies were found affecting 9 different medications. The average number of discrepancies per patient that presented with a discrepancy was 1.71 discrepancies. Five of the 12 discrepancies affected both the measured creatinine clearance and the rounded creatinine clearance, while 7 of the 12 discrepancies affected only the rounded creatinine clearance.
Conclusion: Results of the study show that patients in CKD Stage 3, or in CKD Stage 2 but within approximately 16 mL/min of CKD Stage 3, are more likely to present with renal dosing discrepancies, and that the discrepancies identified were not localized to particular medications or therapeutic areas.
Roden, Kelly Lynn, "Evaluating the non-evidence based practice of rounding serum creatinine in the
elderly and the impact on medication dosing" (2015). Undergraduate Honors Thesis Collection. 311.