What are the laboratory findings that suggest someone may have Chronic Kidney Disease (CKD)?

From the Guidelines

Laboratory findings suggestive of chronic kidney disease (CKD) primarily include a reduced estimated glomerular filtration rate (eGFR) below 60 mL/min/1.73m² and albuminuria or proteinuria, measured as albumin-to-creatinine ratio (ACR) ≥30 mg/g in spot urine samples, as indicated by the most recent guideline 1. These findings are crucial for the detection and diagnosis of CKD. The eGFR is a key indicator of kidney function, and its reduction is a definitive diagnostic criterion for CKD. Albuminuria or proteinuria is another important marker of kidney damage. Some key laboratory findings that may suggest CKD include:

• Elevated serum creatinine and blood urea nitrogen (BUN) levels, which indicate decreased kidney filtration capacity
• Electrolyte imbalances such as hyperkalemia, hyperphosphatemia, hypocalcemia, and metabolic acidosis (decreased bicarbonate levels)
• Normocytic anemia due to decreased erythropoietin production, as revealed by complete blood count
• Hematuria, pyuria, casts, or abnormal sediment in urinalysis
• Structural abnormalities identified by imaging studies and kidney ultrasound The KDIGO 2024 clinical practice guideline for the evaluation and management of CKD recommends testing people at risk for and with CKD using both urine albumin measurement and assessment of GFR, and repeating tests to confirm the presence of CKD after incidental detection of elevated urinary albumin-to-creatinine ratio (ACR), hematuria, or low estimated GFR (eGFR) 1. It is essential to note that the diagnosis of CKD should be based on the presence of kidney damage or decreased kidney function for 3 or more months, as defined by the national kidney foundation practice guidelines for chronic kidney disease 1. In clinical practice, the detection and diagnosis of CKD should be guided by the most recent and highest-quality evidence, such as the KDIGO 2024 clinical practice guideline 1, to ensure optimal patient outcomes in terms of morbidity, mortality, and quality of life.

From the Research

Lab Findings for CKD

The following lab findings suggest someone may have Chronic Kidney Disease (CKD):

• Estimated glomerular filtration rate (eGFR) of less than 60 mL/min per 1·73 m2 2
• Presence of albuminuria (or proteinuria) 3, 4, 2
• Elevated serum creatinine levels 3, 4, 5
• Abnormal urine albumin-to-creatinine ratio (uACR) or urine protein-to-creatinine ratio 3, 4, 6
• Low eGFR and high uACR are associated with increased risk of progression of CKD and death 2, 5

Key Laboratory Tests

The key laboratory tests used to diagnose and stage CKD are:

• Serum creatinine assay, which should be traceable to isotope dilution mass spectrometry (IDMS) method and have minimal bias and acceptable imprecision 3
• eGFR, which should be estimated using the 2009 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation 3, 4
• Urine albumin-to-creatinine ratio (uACR) or urine protein-to-creatinine ratio 3, 4, 6
• Cystatin C measurement, which can be used to confirm GFR if necessary 4

Limitations and Variations

It is essential to note that:

• Creatinine measurement has limitations, and laboratories should provide adequate information on these limitations 3
• Different equations and methods can be used to estimate GFR, and the choice of equation may affect the results 4, 5
• Biomarker measurements can be diverse, and harmonization of these measurements is needed to better establish their clinical significance 5