What percentage of kidney disease can be detected using serum creatinine (creatinine) and urinalysis (urine analysis)?

Detection of Kidney Disease Using Serum Creatinine and Urinalysis

Using serum creatinine and urinalysis alone will detect approximately 80-85% of chronic kidney disease cases, but these tests may miss early kidney damage, especially in certain populations such as the elderly and those with normal GFR but albuminuria. 1, 2

Understanding CKD Detection Methods

Serum Creatinine and eGFR

• Serum creatinine alone is an inadequate screening test for kidney disease 1, 3

• Limitations of serum creatinine:

  • GFR must decline to approximately half the normal level before serum creatinine rises above the upper limit of normal 1
  • In elderly patients, serum creatinine may remain normal despite significant GFR decline due to reduced muscle mass 4
  • Among older adults with stage 3 CKD, 80.6% had creatinine values ≤1.5 mg/dl 4

• eGFR calculation improves detection:

  • The CKD-EPI equation is recommended over the MDRD equation for reporting eGFR 1, 2
  • Clinical laboratories should report eGFR using prediction equations in addition to serum creatinine 1

Urinalysis and Albumin Detection

• Urinary albumin-to-creatinine ratio (ACR) is superior to total protein for CKD detection 1, 2
• Random spot urine samples are preferred over timed collections 1
• ACR categories:
  • Normal: <30 mg/g
  • Increased (formerly microalbuminuria): 30-300 mg/g
  • Severely increased (formerly macroalbuminuria): >300 mg/g 1

Diagnostic Accuracy of Combined Testing

What These Tests Detect

• eGFR <60 mL/min/1.73m² identifies decreased kidney function
• ACR ≥30 mg/g identifies kidney damage even with normal GFR
• Combined testing improves detection significantly 5

What These Tests Miss

• Early kidney damage with preserved GFR and no albuminuria
• In a major study, 16% of participants without CKD by creatinine-based methods had CKD detected by either ACR or cystatin C 5
• Approximately 24% of participants classified as having CKD by creatinine did not have CKD by either ACR or cystatin C 5

Improving Detection Rates

Triple-Marker Approach

• Adding cystatin C to creatinine and ACR improves detection and risk prediction 5
• For borderline eGFR (45-59 mL/min/1.73m²) without albuminuria, measuring cystatin C can confirm CKD diagnosis 1, 2

Repeat Testing

• Confirm abnormal results within 3 months to establish chronicity 2
• 37% of persons with microalbuminuria and normal GFR did not have albuminuria on repeat testing 2 months later 1

Special Populations

Elderly Patients

• High prevalence of stage 3 CKD despite normal serum creatinine 4
• Optimal cutoff values for detecting CKD in older adults:
  • ≥1.3 mg/dl for men
  • ≥1.0 mg/dl for women 4

Diabetic Patients

• Regular screening with both eGFR and ACR is essential
• Serum creatinine with eGFR should be assessed at least annually in all adults with diabetes, regardless of the degree of urine albumin excretion 1

Common Pitfalls to Avoid

1. Relying solely on serum creatinine without calculating eGFR
2. Failing to test for albuminuria when screening for CKD
3. Not confirming abnormal results with repeat testing
4. Misinterpreting normal creatinine in elderly patients as normal kidney function
5. Using total protein instead of albumin for urinary testing

By combining serum creatinine (with eGFR calculation) and urinalysis with ACR measurement, clinicians can detect the majority of CKD cases, but should be aware that approximately 15-20% of cases may still be missed, particularly early kidney damage with preserved filtration.