Is assessing kidney function with serum creatinine and then electrolytes and Blood Urea Nitrogen (BUN) a good practice in cost-sensitive areas?

Assessing Kidney Function in Cost-Sensitive Areas: A Stepwise Approach

Starting with serum creatinine before proceeding to electrolytes and BUN is an appropriate and cost-effective approach for kidney function assessment in resource-limited settings. 1

Evidence-Based Approach to Kidney Function Assessment

Initial Assessment

• Serum creatinine is the primary test for initial kidney function assessment
  • Provides estimation of glomerular filtration rate (eGFR)
  • Low cost and widely available globally 1
  • Should be used as the first-line test in cost-sensitive areas

Stepwise Testing Algorithm

1. First step: Measure serum creatinine to estimate GFR
2. Second step: Add electrolytes if abnormal creatinine or clinical suspicion warrants
3. Third step: Add BUN if further assessment of kidney function is needed

Cost Considerations in Resource-Limited Settings

The KDIGO Controversies Conference specifically addressed this issue, recognizing that:

• The cost of measuring multiple kidney markers simultaneously may be prohibitive in low and middle-income countries (LMICs) 1
• In resource-limited settings, creatinine testing alone is an acceptable first step 1
• This stepwise approach allows for appropriate resource allocation while still providing essential clinical information

Adapting Testing Based on Resource Availability

For Low-Resource Settings

• Creatinine testing alone as initial screen is appropriate 1
• Dipstick testing for albuminuria can be added as a low-cost complement if proteinuria is suspected 1
• Follow up with electrolytes and BUN only when indicated by abnormal creatinine or clinical presentation

For Higher-Resource Settings

• The "triple marker" panel (creatinine, cystatin C, and urine albumin-to-creatinine ratio) provides more comprehensive assessment 1
• However, this is primarily recommended for high-income settings where cost constraints are less significant 1

Clinical Implications and Considerations

Benefits of the Stepwise Approach

• Reduces unnecessary testing costs
• Focuses resources on patients most likely to benefit from additional testing
• Aligns with global recommendations for cost-effective CKD screening 1, 2

Limitations to Consider

• Serum creatinine alone has limitations in accurately estimating GFR 3
• May miss early kidney disease if not combined with albuminuria testing 4
• In patients with complex conditions (e.g., complex stones, abnormal anatomy), additional testing may be required regardless of cost constraints 1

Implementation Guidance

• Use local laboratory reference ranges for interpretation
• Consider point-of-care creatinine testing in settings where laboratory access is limited 5
• For patients with suspected kidney stones or urological conditions, follow the stepwise approach but have a lower threshold for additional testing 1

This stepwise approach to kidney function assessment balances clinical necessity with resource constraints, making it particularly suitable for cost-sensitive healthcare environments while still providing essential diagnostic information for patient care.