Kidney Biomarkers
1. Serum Creatinine
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Most widely used marker of kidney function.
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Simple, inexpensive, rapid.
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Used to calculate eGFR.
Limitations: Depends on muscle mass, hydration, diet.
2. Blood Urea Nitrogen (BUN / Urea)
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Easy, cheap test to assess renal function.
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High levels suggest reduced GFR or dehydration.
Limitations: Affected by diet, GI bleeding, steroids.
3. Estimated GFR (eGFR)
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Not a lab test itself; automatically calculated from creatinine ± cystatin C.
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Standard indicator of CKD staging.
4. Urine Albumin (Spot Urine ACR)
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Most important early marker of kidney damage (especially in diabetes).
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Simple spot urine test → Albumin/Creatinine Ratio (ACR).
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Detects microalbuminuria early.
5. Urinalysis (Routine Urine Examination)
Includes:
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Protein (dipstick)
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Blood
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Glucose
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Specific gravity
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pH
Clinical significance:
Good for screening kidney disease, infections, and glomerular/tubular abnormalities.
6. Urine Protein-to-Creatinine Ratio (PCR)
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Simple spot urine test.
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Used to quantify proteinuria without 24-hour urine.
7. Electrolytes (Na⁺, K⁺, Cl⁻, HCO₃⁻)
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Basic metabolic panel.
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Helpful in evaluating renal tubular disorders, acid–base status, AKI/CKD.
8. Serum Cystatin C (Increasingly available)
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Many labs can now perform it easily.
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More reliable GFR indicator when creatinine is inaccurate.
(Although more “advanced” than creatinine, it is now commercially available and easy to order.)
9. Urine Microscopy
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Simple in most hospitals.
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Can identify:
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RBC casts → Glomerulonephritis
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WBC casts → Pyelonephritis / interstitial nephritis
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Granular casts → ATN
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Crystals → Stones or drugs
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10. 24-Hour Urine Tests
Easy but require patient cooperation:
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Total protein
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Creatinine clearance
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Electrolyte excretion
Not routine, but available everywhere.