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Renal
Creatinine
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Serum creatinine, derived from muscle creatine, is freely filtered and is the standard marker used to estimate glomerular filtration rate (eGFR). Values depend on muscle mass.
Reference interval
| Conventional (mg/dL) | SI (µmol/L) | |
|---|---|---|
| Men | 0.7–1.3 mg/dL | 62–115 µmol/L |
| Women | 0.6–1.1 mg/dL | 53–97 µmol/L |
Specimen: Serum or plasma · Conventional × 88.4 = SI
Causes of high values
Acute kidney injury and chronic kidney disease, pre-renal states, urinary obstruction, high muscle mass, rhabdomyolysis, high meat intake, and drugs that block tubular secretion (trimethoprim, cimetidine).
Causes of low values
Low muscle mass (elderly, malnutrition, amputation, muscle wasting), pregnancy, and overhydration.
Pre-analytical and method notes
Creatinine rises only after a substantial fall in GFR and lags behind acute change, so a normal value does not exclude reduced function. Enzymatic and Jaffe methods differ (Jaffe is affected by glucose, ketones and some drugs); interpret with eGFR equations as recommended by KDIGO. Reference intervals vary by laboratory, age, sex and ethnicity of the calibration population. 1 mg/dL equals 88.4 µmol/L.
References
- Rifai N, Horvath AR, Wittwer CT. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Elsevier, 6th edition (2018) — Tier 3 (textbook)
- KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Disease: Improving Global Outcomes (2013) — Tier 2 (guidelines / primary literature)
- KDIGO Clinical Practice Guideline for Acute Kidney Injury. Kidney Disease: Improving Global Outcomes (2012) — Tier 2 (guidelines / primary literature)
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