What are the guidelines for diagnosing chronic kidney disease?

Guidelines for Diagnosing Chronic Kidney Disease

Chronic kidney disease is diagnosed when either kidney damage OR a GFR <60 mL/min/1.73 m² persists for 3 months or longer. 1

Core Diagnostic Criteria

CKD requires meeting one or both of the following criteria for ≥3 months: 2, 1, 3

Criterion 1: Evidence of Kidney Damage (at any GFR level)

• Persistent proteinuria is the principal marker - albumin-to-creatinine ratio (ACR) ≥30 mg/g in untimed spot urine samples 2
• Sex-specific cutpoints: >17 mg/g in men and >25 mg/g in women 2, 1
• Other markers include abnormal urine sediment, blood/urine chemistry abnormalities, or abnormal imaging findings 2

Criterion 2: Decreased Kidney Function

• GFR <60 mL/min/1.73 m² alone is sufficient for diagnosis, even without other damage markers 1, 4
• This threshold represents loss of half or more of normal adult kidney function 2
• Normal GFR in young adults is approximately 120-130 mL/min/1.73 m² and declines with age 2

GFR Estimation Methods

Preferred Equation

• Use the CKD-EPI equation for estimating GFR from serum creatinine - it has less bias than the older MDRD equation, especially at GFR ≥60 mL/min/1.73 m² 1, 5
• The CKD-EPI equation adjusts for age, sex, and ethnicity 5

Confirmation Strategy for Borderline Cases

• For patients with eGFR 45-59 mL/min/1.73 m² without albuminuria or other damage markers, measure cystatin C to confirm the diagnosis 1
• This is critical because this group represents 41% of persons in the U.S. estimated to have CKD based on creatinine alone 1
• Cystatin C appears more sensitive than creatinine as a GFR marker 5

Screening Recommendations

Who Should Be Tested

All persons should be assessed during routine health encounters for increased risk based on: 2

• Diabetes mellitus 2
• Hypertension 2
• Age >60 years 2
• Family history of chronic kidney disease 2
• U.S. racial or ethnic minorities 2

Testing Protocol for At-Risk Individuals

• Measure serum creatinine and calculate eGFR 2
• Obtain spot urine for albumin-to-creatinine ratio 2
• Repeat abnormal findings to confirm persistence for ≥3 months before diagnosing CKD 2, 3

CKD Staging System

Once diagnosed, stage CKD by GFR level: 6, 3

• Stage 1: Kidney damage with GFR ≥90 mL/min/1.73 m² 6
• Stage 2: Kidney damage with GFR 60-89 mL/min/1.73 m² 6
• Stage 3: GFR 30-59 mL/min/1.73 m² (subdivided into 3a: 45-59 and 3b: 30-44) 3
• Stage 4: GFR 15-29 mL/min/1.73 m² 6
• Stage 5: GFR <15 mL/min/1.73 m² or dialysis 6

Critical Diagnostic Pitfalls to Avoid

Laboratory Reporting Issues

• Do not use creatinine clearance or estimated creatinine clearance - these overestimate GFR and lead to misclassification 1
• Ensure laboratories report ACR and protein-to-creatinine ratio in untimed urine samples, not just concentrations alone 1
• The term "microalbuminuria" should be discontinued in laboratory reporting 1

Misdiagnosis in Specific Populations

• Do not diagnose CKD in patients with eGFR ≥60 mL/min/1.73 m² unless they have documented markers of kidney damage 1
• In elderly patients, decreased GFR is an independent predictor of adverse outcomes (death, CVD) and requires the same diagnostic criteria regardless of age 2
• Approximately 17% of persons >60 years have eGFR <60 mL/min/1.73 m² 2

Confirmation Requirements

• A single abnormal test is insufficient - abnormalities must persist for ≥3 months to meet diagnostic criteria 2, 1, 3
• Less than 5% of patients with early CKD report awareness of their disease, emphasizing the importance of systematic screening 3

Clinical Awareness Context

• CKD affects 8-16% of the population worldwide and is the 16th leading cause of years of life lost 3
• Cardiovascular disease events are more common than kidney failure in CKD patients, making early detection critical for CVD risk reduction 2
• Patients with CKD should be considered in the highest risk group for subsequent CVD events 2