Basic Laboratory Tests for CKD Follow-Up
For routine CKD follow-up, order serum creatinine with eGFR calculation and urine albumin-to-creatinine ratio (ACR) as your core tests—these two measurements form the foundation of CKD monitoring and risk stratification. 1, 2
Core Laboratory Panel
The KDIGO 2024 guidelines establish a clear framework for CKD monitoring based on two essential measurements:
Primary Tests (Required for All CKD Patients)
- Serum creatinine with calculated eGFR using creatinine-based equation (eGFRcr)
- Urine albumin-to-creatinine ratio (ACR) from a spot urine sample
These two tests allow you to stage CKD using the CGA classification system (Cause, GFR category, Albuminuria category) and track disease progression over time 1, 2.
Enhanced GFR Assessment When Needed
Add cystatin C measurement when eGFR based on creatinine alone may be inaccurate (Grade 1C recommendation). Calculate eGFRcr-cys (combined creatinine and cystatin C equation) in situations where:
- Treatment decisions depend on precise GFR assessment
- Creatinine-based eGFR seems discordant with clinical picture
- Extremes of muscle mass or dietary protein intake exist 2
Establishing Chronicity
Repeat abnormal tests at minimum 3-month intervals to confirm CKD diagnosis. A single abnormal eGFR or ACR could represent acute kidney injury or acute kidney disease rather than chronic disease 1, 2. However, if clinical context strongly suggests CKD (imaging showing small kidneys, known longstanding risk factors), you can initiate CKD-specific treatments without waiting 3 months 1.
Additional Tests for Cause Evaluation
When establishing or reassessing CKD etiology, the guidelines recommend a targeted approach based on clinical context 1:
Chemistry and Electrolyte Panel
- Acid-base status
- Electrolytes (sodium, potassium, bicarbonate, calcium, phosphate)
Urinalysis with Microscopy
- Critical for differential diagnosis—persistent hematuria or specific urine sediment findings guide whether serologic testing or biopsy is needed
- Distinguishes glomerular from tubulointerstitial disease
Serologic Tests (When Glomerular Disease Suspected)
- Anti-PLA2R antibodies
- ANCA panel
- Anti-GBM antibodies
- Serum-free light chains
- Serum and urine protein electrophoresis/immunofixation
The guidelines emphasize that monoclonal gammopathy of renal significance (MGRS) is increasingly recognized even without multiple myeloma, making light chain assessment important in appropriate clinical contexts 1.
Common Pitfalls to Avoid
Do not assume a single elevated creatinine or ACR represents chronic disease—acute processes can mimic CKD. Always confirm with repeat testing unless clinical indicators strongly support chronicity 1, 2.
Do not rely solely on creatinine-based eGFR in patients with extremes of body composition—muscle mass significantly affects creatinine levels. Add cystatin C in these situations for more accurate assessment 2.
Do not order extensive serologic panels reflexively—the presence or absence of hematuria and the pattern of proteinuria should guide which additional tests are truly needed 1.
Frequency of Monitoring
While the guidelines establish what to test, the frequency depends on CKD stage and risk category. Higher KDIGO risk categories (based on combined GFR and albuminuria staging) warrant more frequent monitoring, though recent evidence suggests monthly testing in stable patients may be excessive 3.
The algorithmic approach is straightforward: Start with creatinine/eGFR + ACR → Repeat to confirm chronicity → Add cystatin C if accuracy matters for decisions → Add cause-specific tests only when clinical features suggest specific etiologies.