Is a creatinine clearance (CrCl) of 54 mL/min indicative of normal renal function in a 70-year-old female?

From the Guidelines

No, a creatinine clearance (CrCl) of 54 mL/min is not indicative of normal renal function in a 70-year-old female.

Renal Function Decline with Age

• The normal level of GFR varies according to age, sex, and body size, with a decline in GFR of approximately 12-15 mL/min per decade after the age of 40 1.
• A GFR level less than 60 mL/min per 1.73 m2 represents a loss of half or more of the adult level of normal kidney function, and the prevalence of complications of chronic kidney disease increases below this level 1.

Estimating GFR

• The Modification of Diet in Renal Disease (MDRD) study and Cockcroft-Gault equations provide useful estimates of GFR in adults, taking into account serum creatinine concentration, age, sex, race, and body size 1.
• The MDRD study equation is more accurate and precise than the Cockcroft-Gault equation for persons with a GFR less than approximately 90 mL/min per 1.73 m2, but its generalizability is limited in certain populations, including those older than 70 years of age 1.

Clinical Implications

• Decreased GFR in the elderly is an independent predictor of adverse outcomes, such as death and cardiovascular disease, and requires adjustment in drug dosages 1.
• A CrCl of 54 mL/min in a 70-year-old female suggests impaired renal function, which may necessitate careful monitoring and adjustment of medications to prevent adverse outcomes.

From the Research

Renal Function Assessment

• Creatinine clearance (CrCl) is a measure of renal function, with lower values indicating impaired kidney function.
• A CrCl of 54 mL/min in a 70-year-old female may not be considered normal, as studies have shown that renal function declines with age 2.
• The Cockcroft-Gault equation is a commonly used method to estimate CrCl, and it takes into account age, weight, and sex 3, 4, 5.

Age-Related Decline in Renal Function

• Renal function declines with age, and this decline can be underestimated by serum creatinine levels alone 2.
• In older adults, a significant proportion of those with normal serum creatinine levels may have impaired renal function, as measured by CrCl or estimated glomerular filtration rate (eGFR) 2.
• Female sex and older age are associated with a higher risk of misclassification of renal function based on serum creatinine levels alone 2.

Comparison of CrCl Estimation Methods

• The Cockcroft-Gault equation is considered a reliable method for estimating CrCl, especially in older adults 3, 5.
• The Modification of Diet in Renal Disease (MDRD) formula may overestimate CrCl in older adults, leading to misclassification of renal function 3.
• Measured CrCl from 24-hour urine collection is considered the gold standard, but it may not always be practical or accurate 6, 5.

Clinical Implications

• Accurate assessment of renal function is crucial for drug dosing and management of comorbidities in older adults 4, 2.
• Using estimated CrCl, rather than serum creatinine alone, can help identify patients with impaired renal function and guide clinical decision-making 4, 2.