Cystatin –C:
Why Cystatin-C Test?
CLINICAL INFORMATION
Cystatin – C is also called cystatin 3 (formerly known as gamma trace, post-gammaglobulin, neuro-endocrine basic polypeptide). Cystatin – C is a low molecular weight protein synthesized by all nucleated cells and is found in many body fluids such as blood, spinal fluid and breast milk etc. In normal healthy individuals generally Cystatin – C is filtered out from the blood and is excreted in the urine (usually Cystatin C is not found at detectable levels in the urine). The physiological function of Cystatin – C is to inhibit the breakdown of other proteins i.e cysteine protease (lysosomal proteinase). Cystatin – C is used as a marker tool in the diagnostics for assessment of kidney function and also in cardiovascular diseases (deteriorating myocardial function). Cystatin – C is effectively filtered by the glomerulus and fully broken down by the renal tubules for recycling. Hence increased level of serum or plasma Cystatin – C correlates closely with the glomerular filtration rate - GFR, hence is used to calculate GFR (concentration of serum Cystatin – C levels progressively increased as GFR is reduced eg. Kidney dysfunction etc). Even though Cystatin – C is considered as an emerging tool (gaining acceptance for its usefulness) for diagnosis, still some schools of thought suggest that there is still a degree of uncertainty about when and how it should be used. Thus Cystatin – C (i.e high levels of Cystatin – C reflects the severity of chronic kidney disease) acts as an excellent indicator of kidney function and is used to monitor the progression of kidney diseases. Higher levels of Cystatin – C is also be caused by certain pathologies such as diabetes, cancer, HIV, rheumatic diseases, hypothyroidism and/or hyperthyroidism, use of steroids etc. While low levels of Cystatin – C are found in certain pathologies such as atherosclerosis, aneurysms, cognitive dysfunction and Alzheimer’s disease (since Cystatin – C involves in brain disorders involving amyloid protein deposition and also Cystatin 3 binds with beta-amyloid hence reduces its aggregation and deposition) etc. Factors that affect Cystatin – C levels are age (older patients), gender (male), weight (obesity), height (Taller patients), cigarette smoking, higher levels of C-Reactive Protein levels etc. Additional tests include estimation of creatinine levels (Cystatin – C is a more sensitive marker than creatinine since Cystatin – C is more significantly increased than serum creatinine levels and therefore gives a stronger signal in comparison in the measurement of GFR), albuminuria, BUN etc in sample specimens. Other tests include inulin test for GFR, radio-isotopic studies such as51 chromium-EDTA, 125 I-iothalamate, 99mTc-DTPA or radio-contrast agents such as iohexol (these tests are now outdated and moreover due to its potential health hazards).
General Instructions:
Sample Requirement: Specimen –As guided by the physician -preferably Urine specimen (But also in a blood sample collected from the vein if suggested by the pathologist). Test Preparation: None.
NOTE - Sample for specimen collections may vary based on the patient’s condition/cases according to patient’s presenting complaints/signs or symptoms:
SPECIMEN REQUIREMENT (Special or Rare Cases) - As instructed and guided by Physician / Clinician / Pathologist / as per Laboratory’s requirements, according to procedures and protocols.
This Multi-Specialty Clinical Referral Laboratory RTDIAGNOSTICS provides precise and accurate tests with an extensive range of testing services to the medical centres to help in the diagnosis and identification of pathology in the test specimens for infectious diseases and also to evaluate the function of organ systems of the patient. It prevents further complications and helps to stabilize and restore health to near normalcy at the earliest without delay.
