Laboratory Tests for Renal Insufficiency

Core Laboratory Tests

The American College of Physicians recommends serum creatinine as the primary marker for kidney function assessment, which should be measured using a specific assay with calibration traceable to international standard reference materials 1
The National Kidney Foundation prefers estimated glomerular filtration rate (eGFR) calculated using the 2009 CKD-EPI equation over relying on serum creatinine concentration alone 1
Blood urea nitrogen (BUN) should be measured alongside creatinine, as the BUN-to-creatinine ratio helps differentiate between prerenal, intrinsic renal, and postrenal causes 2
Urinalysis with microscopy to detect proteinuria, hematuria, and cellular casts that may indicate kidney damage is recommended by the Clinical Infectious Diseases society 3, 4
Urine protein quantification using spot urine albumin-to-creatinine ratio (ACR) or protein-to-creatinine ratio (PCR) from a first morning sample is suggested by the Kidney International guidelines 3, 1
Electrolytes including sodium, potassium, chloride, calcium, phosphorus, and bicarbonate to evaluate electrolyte imbalances and acid-base status should be measured, as recommended by the Journal of the National Comprehensive Cancer Network 2, 5

The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines define G1 as ≥90 mL/min/1.73m² (Normal or high GFR) 3, 6
The KDIGO guidelines define G2 as 60-89 mL/min/1.73m² (Mildly decreased GFR) 3, 6
The KDIGO guidelines define G3a as 45-59 mL/min/1.73m² (Mildly to moderately decreased GFR) 3, 6
The KDIGO guidelines define G3b as 30-44 mL/min/1.73m² (Moderately to severely decreased GFR) 3, 6
The KDIGO guidelines define G4 as 15-29 mL/min/1.73m² (Severely decreased GFR) 3, 6
The KDIGO guidelines define G5 as <15 mL/min/1.73m² (Kidney failure) 3, 6

Cystatin C can be used as a confirmatory test when eGFR based on serum creatinine may be less accurate, according to the Praxis Medical Insights guidelines 1
Renal ultrasound to evaluate kidney size and rule out obstruction in patients with evidence of CKD is recommended by the Clinical Infectious Diseases society 3, 7
24-hour urine collection for more precise measurement of protein excretion and creatinine clearance when needed is suggested by the Praxis Medical Insights guidelines 4

Patients with monoclonal gammopathies or multiple myeloma require specialized assessment including serum free light chain measurement, urine protein electrophoresis, and serum protein electrophoresis, as recommended by the Journal of the National Comprehensive Cancer Network 5
HIV-infected patients should be screened with urinalysis for proteinuria and eGFR calculation, with annual follow-up for those at high risk, according to the Clinical Infectious Diseases society 3, 7

A single abnormal test result is insufficient for diagnosis of chronic kidney disease; persistence of abnormalities for >3 months is required, as stated by the Praxis Medical Insights guidelines 1
Certain medications and substances can interfere with creatinine measurements, affecting eGFR accuracy, according to the Praxis Medical Insights guidelines 1

Patients with confirmed CKD should have monitoring frequency guided by GFR category, albuminuria category, and rate of progression, as recommended by the Praxis Medical Insights guidelines 1
More frequent monitoring is warranted for patients with rapidly declining kidney function or those at higher risk for progression, according to the Praxis Medical Insights guidelines 1