From the Guidelines
Cystatin C levels are elevated in conditions that impair renal function, including chronic kidney disease, acute kidney injury, and other kidney disorders, as well as certain non-renal factors such as thyroid dysfunction and inflammation, as supported by recent studies 1.
Conditions Causing Elevated Cystatin C Levels
The following conditions can lead to elevated cystatin C levels:
- Chronic kidney disease (CKD)
- Acute kidney injury (AKI)
- Diabetic nephropathy
- Hypertensive nephropathy
- Glomerulonephritis
- Thyroid dysfunction (particularly hyperthyroidism)
- Uncontrolled diabetes
- Inflammation
- Certain malignancies
- Glucocorticoid therapy
- Age-related changes, as kidney function naturally declines with aging
- Medications like cyclosporine and tacrolimus, which may increase levels due to their nephrotoxic effects
Importance of Cystatin C in Assessing Kidney Function
Cystatin C is a valuable marker of glomerular filtration rate (GFR) and is less affected by muscle mass compared to creatinine, making it particularly useful for assessing kidney function in:
- Elderly patients
- Children
- Those with muscle wasting As noted in a study published in 2022, equations based on cystatin C alone or in combination with creatinine, such as CKD-EPI Cr-cystatin C, are more accurate than creatinine-based equations in older people 1.
Clinical Utility of Cystatin C
Cystatin C can be used to:
- Confirm the diagnosis of CKD
- Monitor kidney function in patients with CKD or AKI
- Assess the risk of cardiovascular disease and mortality in patients with CKD
- Guide medication dosing and adjust for renal impairment, as recommended by the European Society of Cardiology working group on cardiovascular pharmacotherapy 1.
Recent Guidelines and Recommendations
Recent guidelines and recommendations, such as those from the Kidney Disease Outcomes Quality Initiative (KDOQI) and the European Society of Cardiology, emphasize the importance of using cystatin C in combination with other markers, such as creatinine and urinary albumin-creatinine ratio (UACR), to assess kidney function and guide clinical decision-making 1.
From the Research
Conditions Causing Elevation in Cystatin C Levels
Elevation in cystatin C levels can indicate impaired renal function. The following conditions can cause an increase in cystatin C levels:
- Acute kidney injury (AKI) 2, 3, 4
- Chronic kidney disease (CKD) 2, 5, 6
- Contrast-induced acute kidney injury 2
- Acute tubular necrosis 4
- Malignancy 3, 4
- Diabetes mellitus 4
- Heart failure 4
- Thyroid disorder 4
Factors Affecting Cystatin C Levels
Several factors can affect cystatin C levels, including:
Relationship Between Cystatin C and Renal Function
Cystatin C is a reliable marker for the early diagnosis and prognosis of contrast-induced acute kidney injury 2. It is also an accurate biomarker for the early detection of AKI 3 and can predict renal recovery earlier than creatinine among patients with AKI 4. Additionally, serum cystatin C is an independent biomarker associated with the renal resistive index in patients with CKD 6.