Introduction of cystatin C

In 1983 Anastasi, etc. for the first time in the egg white separation and purification of high-purity cysteine proteinase inhibitor (cysteine proteinase inhibitor, CPI) was named cystatin C is a cysteine protease inhibitor, also Known as γ-trace protein and γ-globulin, widely found in various tissues of nucleated cells and body fluids, is a low molecular weight, basic non-glycosylated protein, molecular weight of 13.3KD, by the 122 amino acid residues Based composition, can be produced by all the nucleated cells of the body, a constant rate. Cystatin C in the circulation is removed only by glomerular filtration, an endogenous marker that reflects changes in glomerular filtration rate and reabsorbed in the proximal tubule but is completely reabsorbed Metabolic decomposition, does not return to the blood, therefore, its blood concentration determined by glomerular filtration, without relying on any external factors, such as gender, age, diet, is a reflection of glomerular filtration rate changes in the ideal Homologous markers.

The history of cystatin C

Due to the lack of appropriate detection technology has not been widely used until 1994, Kyhse Andersen J and other reports of particle-enhanced transmission turbidimetric immunoassay method (particle enhanced turbidmetric immunoassay) and Finney H and other reports in 1997 particle-enhanced immunoturbidimetric turbidimetric method Particle enhanced nephelometic immunoassay, both of which are capable of measuring Cystatin C on an automated biochemical analyzer and are fast and stable. So that cystatin C can be more convenient for clinical applications.

The traditional habit of urea nitrogen, creatinine as a routine test of renal function, but the kidneys have a strong reserve capacity and compensatory ability in glomerular damage early or mild damage, blood urea nitrogen, creatinine Can be maintained at normal levels, only in severe glomerular damage, the general glomerular filtration rate decreased by 50% or less, blood urea nitrogen, creatinine concentration was significantly increased

The incidence of hypertension is increased year by year. Renal damage is one of the common complications. Early intervention is of great significance to improve the prognosis of patients with hypertension. Hypertension causes chronic renal damage of hypertension caused by benign small arterial nephrosclerosis. Small arterial nephrosclerosis before clinical symptoms, routine blood and urine tests are normal circumstances, through the application of more sensitive means of inspection can still find some abnormalities, which can be regarded as early renal damage in hypertension.

Diabetic renal damage is a serious chronic diabetic microvascular complications, diabetes is one of the major causes of death, more than 30% of patients with renal failure and the need for renal dialysis, experts believe that, compared with other indicators, CysC detection Diabetic nephropathy with a sensitivity of 40% and a specificity of 100% makes it necessary to periodically measure changes in CysC concentrations in diabetic patients without evidence of nephropathy to observe their association with diabetic microangiopathy.

The adverse effects of acute or chronic rejection or immunosuppressive therapy are the greatest harm after renal transplantation. The early detection of renal injury is beneficial to timely intervention measures. When acute renal rejection occurs in transplanted kidney, serum CysC is increased Which was much earlier than serum Cr.

Research data have shown that, CysC than serum BUN, Cr have higher sensitivity and specificity, for the evaluation of glomerular filtration rate has a very important value, more used particle enhanced immune turbidimetry, technology has become In the mature, simple, less interference factors, the diagnosis of various diseases and disease observation has important clinical significance.

Biological characteristics of cystatin

Cystatin C, also known as γ2 traces the basic protein or post-γ-globulin, cysteine protease inhibitor is a protein in a. The gene encoding Cys C is a housekeeping gene that can be consistently transcribed and expressed at constant rates in all nucleated cells, with no tissue specificity, so Cys C can be produced in vivo at constant velocities and is present in various body fluids, (Cys C in the blood from the age of 1 to 60 years before the constant concentration in the blood), the highest in the cerebrospinal fluid and seminal plasma, the lowest in the urine, not the age, sex, weight, inflammation and other factors. Its molecular weight is small (13KD), physiological conditions with a positive charge, can be free from the glomerular filtration, complete reabsorption of renal tubular epithelial cells and degradation in the cell, not to return to the blood; the same time, renal tubular epithelial cells Does not secrete Cys C to the lumen. Therefore, its serum concentration is mainly determined by the GFR (Cys C naturally become an important indicator of glomerular filtration).

The superiority of cystatin

Cys C is an endogenous substance which has so far substantially met the requirements of ideal endogenous GFR markers. Is a recently developed assessment of renal function, a high sensitivity and specificity of the indicators.

Can replace:

1: ex whole blood test;

2: hour urine collection;

3: y surface area and creatinine clearance rate calculation;

4:tients with irradiation of radioactive substances.

Clinical significance of cystatin

Under normal circumstances, Cys C in serum and plasma concentrations of 0.51-1.09mg / L (reference range). When the renal function is impaired, the concentration of Cys C in the blood changes with the glomerular filtration rate.When renal failure, glomerular filtration rate decreased, Cys C concentration in the blood can increase by 10 times; Glomerular filtration rate is normal, and tubular dysfunction, will prevent the Cys C in the renal tubular absorption and rapid decomposition, so that the concentration of urine increased 100 times.