Module 1: Understanding Chronic Kidney Disease (ckd)

Serum creatinine alone is not adequate

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• Serum creatinine levels reflect muscle mass, age, gender, and race.
• A typical “normal” reference range of 0.6–1.2 mg/dL listed on many lab reports does not account for muscle mass, age, gender, and race.
• A 28-year-old African American man with serum creatinine of 1.2 has an eGFR > 60.
• A 78-year-old white woman with serum creatinine of 1.2 has an eGFR of 43.

Creatinine-based estimates of kidney function have limitations

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• Results may be inaccurate with:
• Rapidly changing creatinine levels
• Example: acute kidney injury
• Extremes in muscle mass, body size, or altered diet patterns
• Medications that interfere with the measurement of serum creatinine
• Use of creatine supplements

Decreased kidney function versus kidney disease

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• Estimating equations are less reliable at higher GFR.
• Kidney function declines with age.
• While there is an association between decreased eGFR and morbidity, even in elderly, this association does not mean causality.
• Use diagnostic terms denoting disease with caution, especially in older people without evidence of kidney damage (e.g. elderly with eGFR 55).

Kidney function and eGFR decline with age

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• Reference Table for Population Mean eGFR from NHANES III

Age (years)	Mean eGFR (mL/min/1.73 m2)
20–29	116
30–39	107
40–49	99
50–80	93
60–69	85
70+	75

• In healthy kidney donors the number of glomeruli per kidney decrease 25% by age 60-69 and GFR declines proportionately.

• Reference: Coresh et al. Am J of Kidney Dis. 2003;41(1):1–12.
• Denic et al. J Am Soc Nephrol. 2017;28(1):313–320.