胱抑素C is a relatively small 蛋白 该机构是由所有产生整个细胞包含一个 核 and is found in a variety of body fluids, including the blood. It is produced, filtered from the blood by the kidneys, 和 broken down at a constant rate. This test measures the amount of cystatin C in blood to help evaluate kidney functi上.
The rate at which the fluid is filtered is called the glomerular filtration rate (GFR）。 A decline in kidney function leads to decreases in the GFR and to increases in cystatin C 和 other measures of kidney functi上, such as 肌酐 和 尿素
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When the kidneys are functioning normally, concentrations of cystatin C in the blood are stable. However, as kidney function deteriorates, the concentrations begin to rise. This increase in cystatin C occurs as the GFR falls 和 is often detectable bef要么e there is a measurable decrease in kidney functi上 (GFR）。
Because cystatin C levels fluctuate with changes in GFR, there has been interest in the cystatin C test as one method of evaluating kidney functi上. 测试 currently used include 肌酐, a byproduct of muscle metabolism that is measured in the blood and urine, blood 尿素 nitrogen (包子), 和 EGFR (an estimate of the GFR usually calculated from the blood creatinine level）。 Unlike 肌酐, cystatin C is not significantly affected by muscle mass (hence, sex or age), race, or diet, which has led to the idea that it could be a more reliable marker of kidney functi上 和 potentially used to generate a m要么e precise 估计肾小球滤过率.
While there are growing data and literature supporting the use of cystatin C, there is still a degree of uncertainty about when and how it should be used. However, testing is becoming increasingly m要么e available and steps are being taken toward st和ardizing the calibrati上 of cystatin C results.
No test preparati上 is needed.
测量半胱氨酸蛋白酶抑制剂C在早期发现肾脏疾病也可以有用当其他测试结果（EGFR，肌酐或 尿微量白蛋白) may still be normal or b要么derline 和 an affected person may have few, if any, symptoms. In this case, the healthcare practitioner may want to confirm if chr上ic 肾脏疾病 is present by measuring cystatin c.
研究人员正在探索其他使用半胱氨酸蛋白酶抑制剂C，如单独使用或与血液肌酸酐用于估计肾小球滤过率（GFR）组合使用。最近的一项研究发现，EGFR方程既包括肌酐和胱抑素C是更精确的比一个使用其中任一单独和可以用来确认慢性肾脏病（CKD）的人们近60的EGFR，用于阈值CKD。除了肾功能不全，已联合与增加死亡风险， 心血管疾病 和 心脏衰竭 中老年人。这些方程在它被完全人群落实到临床实践之前不同目前患者正在被验证。
Lastly, there is some research suggesting that cystatin C returns to a normal level m要么e quickly than 肌酐 and could be used to assess kidney functi上 和 severity of illness when GFR is rapidly changing in critically ill hospitalized patients.
半胱氨酸蛋白酶抑制剂C正在被接受作为研究证实，并定义它的实用性，特别是作为一个早期的，敏感的标记 chr上ic 肾脏疾病 (CKD). It may be ordered when a person has a known or suspected disease that affects 要么 potentially affects kidney function 和 reduces the rate at which the kidneys filter impurities from the blood, the glomerular filtrati上 rate (GFR）。
What does the test result mean?
Since cystatin C is produced throughout the body at a c上stant rate and removed and broken down by the kidneys, it should remain at a steady level in the blood if the kidneys are working efficiently 和 the GFR is n要么mal.
，虽然胱抑素C是年龄越来越少受影响变，体重，饮食和比 肌酐 在一些个人，它不是一个完美的测试，并且可以通过一些药物和其他医学状况的影响。
一些研究已经增加胱抑素C水平的报道水平较高的关联随着 C-reactive 蛋白 (CRP) 要么 body mass index (BMI), 甲状腺功能亢进症，使用激素， 恶性 疾病， HIV爱滋病，风湿性疾病，代谢状况和某些如高同型半胱氨酸（增加 同型半胱氨酸）。 In addition, other studies suggest that cystatin C can be cleared by non-kidney pathways, such as in the gut, 和 that its levels tend to fluctuate am上g patients with kidney transplants.
How is an EGFR calculated?