What are the diagnostic criteria for Chronic Kidney Disease (CKD)?

From the Guidelines

Chronic Kidney Disease (CKD) is diagnosed through a combination of blood tests, urine tests, and imaging studies, with the primary diagnostic criteria including measuring estimated glomerular filtration rate (eGFR) and assessing for albuminuria or proteinuria in urine samples, as recommended by the most recent guidelines 1. The diagnosis of CKD is based on the presence of persistent kidney damage or decreased kidney function for 3 or more months. Key markers of kidney damage include:

• Albuminuria, defined as an albumin-to-creatinine ratio (ACR) of 30 mg/g or greater
• Hematuria
• Abnormalities in kidney imaging results
• History of kidney transplantation The glomerular filtration rate (GFR) is the best measure of overall kidney function, and a GFR level less than 60 mL/min per 1.73 m² represents loss of half or more of the adult level of normal kidney function. Some of the key points to consider when diagnosing CKD include:
• CKD can be diagnosed without knowledge of its cause
• Kidney damage is usually ascertained by markers rather than by kidney biopsy
• Persistent proteinuria is the principal marker of kidney damage
• An ACR greater than 30 mg/g in untimed (spot) urine samples is usually considered abnormal
• Other markers of damage include abnormalities in urine sediment, abnormalities in blood and urine chemistry measurements, and abnormal findings on imaging studies
• Persons with normal GFR but with markers of kidney damage are at increased risk for adverse outcomes of CKD It is essential to note that the diagnosis of CKD has significant implications for patient care and management, and early diagnosis is crucial to slow disease progression and prevent complications. The most recent guidelines recommend using the 2021 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation to estimate GFR from creatinine, age, and sex, without regard to race 1. In clinical practice, CKD screening should start at diagnosis of type 2 diabetes, and screening is recommended commencing 5 years after diagnosis for type 1 diabetes 1. Overall, the diagnosis of CKD requires a comprehensive approach, including laboratory tests, imaging studies, and clinical evaluation, to identify individuals at risk and provide timely interventions to slow disease progression and improve outcomes.

From the Research

Diagnosis of Chronic Kidney Disease (CKD)

The diagnosis of CKD is based on the estimation of glomerular filtration rate (eGFR) and assessment of albuminuria (or proteinuria) 2. The following are key factors in diagnosing CKD:

• Ensure good communication between laboratory professionals and clinicians, such as nephrologists or specialists in general/family medicine 2
• Ensure all patients are provided with the same availability of laboratory diagnostics 2
• Use creatinine assays that are traceable to isotope dilution mass spectrometry (IDMS) method and have minimal bias and acceptable imprecision 2
• Select the appropriate GFR estimating formula, such as the 2009 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation 2, 3
• Report key laboratory tests, including creatinine, eGFR, urine albumin-to-creatinine ratio, and urine protein-to-creatinine ratio, using appropriate reporting units 2

Laboratory Tests for CKD Diagnosis

The following laboratory tests are used to diagnose CKD:

• Serum creatinine measurement to estimate GFR 2, 3
• Urine albumin-to-creatinine ratio (ACR) to assess albuminuria 2, 3, 4
• Urine protein-to-creatinine ratio to assess proteinuria 2
• Cystatin C measurement to estimate GFR in certain cases, such as when serum creatinine is not accurate 3

Staging of CKD

CKD is staged based on the level of eGFR and albuminuria 5, 3. The stages of CKD are:

• Stage 1: eGFR ≥90 mL/min/1.73 m2 and albuminuria ≥30 mg/g 5
• Stage 2: eGFR 60-89 mL/min/1.73 m2 and albuminuria ≥30 mg/g 5
• Stage 3: eGFR 30-59 mL/min/1.73 m2 and albuminuria ≥30 mg/g 5
• Stage 4: eGFR 15-29 mL/min/1.73 m2 and albuminuria ≥30 mg/g 5
• Stage 5: eGFR <15 mL/min/1.73 m2 or kidney failure 5

Risk Assessment and Management

Patients with CKD should undergo risk assessment and management to prevent progression of the disease and reduce the risk of cardiovascular disease and other complications 5, 6. This includes:

• Cardiovascular risk reduction, such as statins and blood pressure management 5
• Treatment of albuminuria, such as angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers 5
• Avoidance of potential nephrotoxins, such as nonsteroidal anti-inflammatory drugs 5
• Adjustments to drug dosing, such as many antibiotics and oral hypoglycemic agents 5