What tests indicate impaired renal function?

From the Guidelines

Impaired renal function can be indicated through several key tests, including the estimated glomerular filtration rate (eGFR), serum creatinine, blood urea nitrogen (BUN), urinalysis for proteinuria or hematuria, the albumin-to-creatinine ratio, cystatin C blood tests, and imaging studies like ultrasound, CT scans, or MRIs. The most recent and highest quality study 1 emphasizes the importance of using the updated, race-free estimated glomerular filtration rate (eGFR) CKD-EPI equations for evaluating kidney function, highlighting the role of cystatin C and the urinary albumin-creatinine ratio (UACR) in CKD screening, diagnosis, and management. Some key points to consider when evaluating kidney function include:

• The eGFR provides the best overall measure of kidney function, with values below 60 mL/min/1.73m² suggesting kidney damage, as noted in 1.
• Urinalysis can detect signs of kidney problems such as proteinuria or hematuria.
• The albumin-to-creatinine ratio in urine specifically measures albumin leakage, with values above 30 mg/g indicating kidney damage, as mentioned in 1 and 1.
• Cystatin C blood tests offer an alternative measurement of filtration rate, particularly useful when creatinine might be misleading, as discussed in 1.
• Imaging studies and kidney biopsies can provide further information on structural abnormalities and tissue examination in complex cases. Given the emphasis on accurate and comprehensive assessment of kidney function, the use of a combination of these tests, guided by the most recent clinical guidelines and practice points, is crucial for the effective diagnosis and management of impaired renal function.

From the Research

Tests for Kidney Function

The following tests are used to indicate impaired renal function:

• Serum creatinine level: This is a widely used test to evaluate renal function, with a glomerular filtration rate (GFR) less than 60 ml/min/1.73 m2 being a significant risk factor for cardiovascular diseases 2.
• Estimated glomerular filtration rate (eGFR): This test is used to assess renal function, and its results are often used in combination with serum creatinine level to evaluate kidney health 2, 3.
• Urine albumin-creatinine ratio (ACR): This test is used to detect albuminuria, a marker of kidney damage, and is considered a more sensitive and quantitative test than the urine dipstick test 4.
• Urine protein-creatinine ratio (PCR): This test is used to assess kidney damage and is similar to ACR in its associations with common complications of chronic kidney disease (CKD) 5.
• Urine dipstick test: This test is a widely used screening tool for albuminuria, but it has poor sensitivity and high false-discovery rates compared to ACR 4.

Additional Tests

Other tests that may be used to indicate impaired renal function include:

• Serum urea level: This test can be used to evaluate renal function, although it is not as commonly used as serum creatinine level 2.
• Microalbuminuria test: This test is used to detect small amounts of albumin in the urine, which can be a marker of kidney damage 2.
• Blood pressure and body mass index (BMI) measurements: These tests can be used to evaluate risk factors for CKD, such as diabetes and hypertension 6.