Understanding Cystatin CCystatin C (Cys-C) is a cysteine protease inhibitor with a molecular weight of 13 kDa, composed of 120 amino acid residues. It is a secretory protein whose excretion is solely influenced by glomerular filtration rate, unaffected by other factors such as gender, age, diet, inflammation, infection, blood lipids, or liver disease. In recent years, the measurement of cystatin C in plasma or serum has gradually been used as a parameter for assessing glomerular filtration rate, thereby determining kidney function. The reference range is 0.51 to 1.09 mg/L.How does cystatin C compare to other indicators, and what are the differences?
Cystatin C testing is similar to creatinine testing, both reflecting kidney function, but the clinical significance of the two differs. Cystatin C is a product of cysteine metabolism in nucleated cells and is a classification of cystatin, originating from the metabolism of cysteine in the body. Creatinine is a metabolic product of the body, primarily produced from muscle tissue metabolism, and is mainly excreted by the kidneys, with 99% of creatinine being eliminated through the kidneys. Therefore, elevated creatinine levels are primarily related to renal insufficiency. The difference is that cystatin C is more sensitive in the early stages than creatinine, rising before creatinine levels increase.What causes elevated cystatin C levels? The detection of cystatin C is becoming increasingly mature, with national and provincial organizations beginning to conduct inter-laboratory quality assessments, leading to more standardized results. Elevated levels can be categorized into physiological and pathological elevations, with specific situations including:1. Physiological elevation:1.1 Drug factors: Toxic drugs that cause kidney damage, such as hormones, can lead to elevated test results.1.2 Lifestyle factors: Alcohol and tobacco can increase the metabolic burden on the kidneys, slowing metabolism and resulting in elevated test results.1.3 Trauma factors: When a patient suffers an injury, damage to the renal area can lead to decreased function, resulting in elevated test results. 2. Pathological factors causing elevation:Diseases such as glomerular disease, diabetic nephropathy, and renal tuberculosis are associated with decreased or lost glomerular filtration rate, leading to the accumulation of toxins and hormones in the body, which in turn increases the concentration of cystatin C.
What further tests should be conducted if cystatin C is elevated? Elevated cystatin C levels may indicate glomerular disease, chronic diabetic nephropathy, renal cancer, etc., necessitating further relevant tests to rule out these diseases, specifically:
1. Glomerular disease: Elevated cystatin C levels, combined with ultrasound: If ultrasound shows reduced kidney size and urinalysis indicates proteinuria or hematuria, glomerular disease may be suggested.
2. Diabetic nephropathy: Elevated cystatin C levels, combined with blood glucose monitoring, diabetes history, and immunofluorescence testing. If blood glucose tests indicate high levels, and the patient has a history of hyperglycemia, with immunofluorescence showing IgG deposition in the renal area, diabetic nephropathy may be indicated.
3. Renal cancer: Elevated cystatin C levels require renal biopsy; if the biopsy reveals cancer cells, renal cancer may be indicated.
What should be noted after discovering elevated cystatin C levels?
1. Follow-up: Regular follow-up at the hospital is necessary, strictly adhering to medical advice regarding medication. Monitor for symptoms such as oliguria, anuria, edema, and adverse reactions to medications like angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists; seek medical attention promptly if discomfort occurs.
2. Lifestyle: Generally, patients are advised to follow a low-salt, low-fat, high-quality protein diet, avoiding spicy and irritating foods. Increase water intake to accelerate kidney metabolism.
3. Psychological support: Patients with glomerular disease, diabetic nephropathy, or renal cancer may face dual psychological and physical challenges; family members and doctors should provide adequate psychological comfort and support for patients to adhere to treatment.
Contributed by: Laboratory Department Guo Yonggang Initial Review: Wang Huafeng
Editor: Xu Haiqing Proofreader: Zhang Bo
Reviewer: Guo Hongwei
