Cystatin C Test: Your Guide to Kidney Health Check

What Is Cystatin C?

Cystatin C is a protein found in all body fluids and produced by cells containing a nucleus. It helps control enzymes by blocking those that break down proteins.

This biomarker is primarily used to assess kidney health, as its levels in the blood reflect the kidneys' ability to filter waste.

Unlike other markers like creatinine, cystatin C levels are less affected by muscle mass. This makes it a more accurate measure for people with different body compositions.

When Is Cystatin C Testing Recommended?

Cystatin C testing is typically prescribed to evaluate kidney function or to detect early signs of kidney disease. It may also provide insights into cardiovascular health.

• Monitor kidney health: In individuals with known kidney issues or at high risk of developing kidney disease.
• Diagnose cardiovascular conditions: Due to its association with vascular health, it may help in assessing atherosclerosis progression, which is the gradual buildup of fatty deposits, cholesterol, and other substances in the walls of arteries.
• Evaluate kidney filtration rates: Particularly in patients for whom creatinine-based measurements are less reliable.
• Screen for at-risk groups: Such as older adults, diabetics, or those with hypertension.

How Is Cystatin C Testing Conducted?

Cystatin C is measured through a simple blood test. This test requires a small sample of blood taken from a vein, which is then analyzed in a lab using special techniques like immunoturbidimetry.

Immunoturbidimetry is a method that measures how much light passes through the sample to determine the level of cystatin C.

The test can be done on its own to specifically check cystatin C levels.

In some cases, it is also included as part of comprehensive panels, such as kidney function panels, to provide a broader analysis of overall kidney health.

Preparations for the Test

• Fasting: Avoid eating for 12 hours before the test to ensure accurate results.
• Physical activity: Refrain from strenuous activity for at least 30 minutes before sample collection.
• Hydration: Stay well-hydrated but avoid excessive fluid intake.

What Are the Normal Cystatin C Levels?

Cystatin C levels can vary based on age. Below are the typical reference ranges:

• Children:
  • Up to 1 year: 0.75–2.85 mg/L
  • 1 to 2 years: 0.77–1.85 mg/L
  • 2 to 19 years: 0.62–1.11 mg/L
• Adults:
  • Up to 49 years: 0.63–1.03 mg/L
  • 50 years and older: 0.67–1.21 mg/L

Note: The units of measurement and the normal ranges can differ depending on the laboratory and the specific methods used

What Do High Levels Mean?

Elevated cystatin C levels suggest reduced kidney function or increased cardiovascular risk. Common causes include:

• Chronic kidney disease: Indicates impaired filtration ability of the kidneys.
• Acute kidney injury: Temporary but severe reduction in kidney function due to illness or injury.
• Cardiovascular conditions: High levels can reflect vascular issues like atherosclerosis.
• Aging: Natural age-related decline in kidney function.

Recommendations

To manage high cystatin C levels:

• Consult a healthcare professional: Get a comprehensive evaluation of kidney and cardiovascular health.
• Adopt a healthy diet: Reduce sodium, saturated fats, and processed foods to support kidney function.
• Stay active: Engage in regular, moderate physical activity to improve overall health.
• Monitor blood pressure and glucose levels: Keep them within recommended ranges.
• Avoid nephrotoxic substances: Reduce or eliminate substances harmful to the kidneys, like excess alcohol or certain over-the-counter drugs.

Which Specialist Should You Consult?

For interpreting cystatin C results or managing related conditions, consult these specialists:

• Nephrologist: Specializes in kidney health and diseases.
• Cardiologist: Evaluates cardiovascular risks associated with abnormal cystatin C levels.
• Urologist: Addresses urinary system concerns that may impact kidney function.
• Internist: Provides a broad approach to systemic health concerns.