Laboratory Monitoring in Chronic Kidney Disease
All patients with CKD require at least annual monitoring of both eGFR and albuminuria (urine albumin-to-creatinine ratio), with more frequent testing based on CKD stage and risk of progression. 1
Core Laboratory Tests
Essential Monitoring Parameters
Kidney Function Assessment:
- eGFR (estimated glomerular filtration rate) should be calculated using creatinine-based equations (preferably CKD-EPI) rather than serum creatinine alone 1, 2
- Urine albumin-to-creatinine ratio (ACR) is the preferred test for proteinuria assessment, measured on a spot urine sample (early morning preferred) 1
- Cystatin C measurement is suggested for adults with eGFR 45-59 mL/min/1.73 m² who lack other markers of kidney damage, to confirm CKD diagnosis 1
Monitoring Frequency by CKD Stage
The frequency of eGFR and ACR monitoring should be risk-stratified 1, 2:
- CKD Stage 3a (eGFR 45-59): Every 6-12 months 2
- CKD Stage 3b (eGFR 30-44): Every 6-12 months 2
- CKD Stage 4 (eGFR 15-29): Every 3-5 months 2
- CKD Stage 5 (eGFR <15): Every 1-3 months 2
Higher albuminuria categories (A2: 30-300 mg/g; A3: >300 mg/g) warrant more frequent monitoring regardless of eGFR 1
Additional Laboratory Parameters
Electrolytes and Acid-Base Status
- Serum potassium must be monitored in all patients on ACE inhibitors, ARBs, or diuretics due to hyperkalemia risk 2
- Serum bicarbonate to assess for metabolic acidosis 2, 3
- Serum sodium as part of comprehensive electrolyte monitoring 2
Mineral and Bone Metabolism
When eGFR falls below 60 mL/min/1.73 m² 2:
- Serum calcium and phosphate for metabolic bone disease screening 2
- Parathyroid hormone (PTH) 2
- 25-hydroxyvitamin D 2
Other Parameters
- Serum albumin for nutritional assessment and as a prognostic marker 3
- Hemoglobin to screen for anemia of CKD 4
Clinically Significant Changes Requiring Evaluation
Be alert to these thresholds that exceed normal variability 1, 2:
- eGFR decline >20% on subsequent testing warrants investigation 1, 2
- eGFR decline >30% after initiating hemodynamically active therapies (ACE inhibitors, ARBs, SGLT2 inhibitors) requires evaluation 1, 2
- Doubling of ACR on subsequent testing exceeds laboratory variability and warrants evaluation 1, 2
High-Risk Populations Requiring Intensified Monitoring
Increase monitoring frequency beyond standard schedules for 2:
- Recent initiation or dose adjustment of hemodynamically active medications
- Rapid eGFR decline (>5 mL/min/1.73 m²/year)
- Diabetes with ACR ≥300 mg/g
- Acute kidney injury episodes
Laboratory Reporting Standards
Clinical laboratories should 1:
- Report eGFR automatically when creatinine is measured 1
- Report ACR (not just albumin concentration alone) 1
- Use enzymatic assays for creatinine (not Jaffe method) to avoid drug interference 1
- Participate in external quality assessment programs 1
- Avoid using the term "microalbuminuria" 1
Common Pitfalls to Avoid
Never rely on serum creatinine alone without calculating eGFR, as this leads to significant errors in assessing kidney function, particularly in elderly patients or those with altered muscle mass 5, 6
Confirm abnormal results before diagnosing CKD: A single elevated ACR ≥30 mg/g should be confirmed with a subsequent early morning urine sample 1
Consider non-GFR determinants of creatinine including muscle mass, diet (high meat intake), and medications that can affect creatinine levels independent of kidney function 5
Do not discontinue SGLT2 inhibitors for initial eGFR declines ≤30%, as this is an expected hemodynamic effect 2