FAQ

Click on any of the questions below to see the answers

 

What is Cystatin C?

Cystatin C is a folded protein structure composed of a chain of 120 amino acids. Cystatin C is a potent cysteine proteinase inhibitor produced at a constant rate by all nucleated cells. Cystatin C is filtered effectively by the glomerulus and fully reabsorbed and broken down by the renal tubules for recycling. A raised level of serum cystatin C correlates closely with GFR and is a good indicator of reduced kidney function. Cystatin C is primarily a marker of kidney function and GFR. However, newer research suggests that cystatin C is a useful marker for a number of other conditions, read more about those situations in the cystatin c clinical use section.

 

What is the Precision of the Gentian cystatin C assay?

Precision studies are carried out as part of application validation and is instrument specific. See instrument specific application notes for more information

 

Isn’t the GFR determined by serum creatinine measurement good enough?

 Creatinine values are dependent on variables including age and body mass and you must correct for this in calculating GFR. Cystatin C GFR gives a direct and accurate measurement of GFR independent of age and muscle mass.

 

What is the “creatinine-blind area”? Doesn’t cystatin C GFR also have a blind area? .

Serum creatinine values are not a direct measure of GFR. GFR can be reduced by as much as 50% while the serum creatinine value is still within the normal range – this is the “creatinine-blind area”. Cystatin C value gives an immediate and true measurement of GFR. Cystatin C doesn’t have a blind area so cystatin GFR is more accurate

 

Serum creatinine is the only relevant test for determining GFR our clinical laboratory offers. How can we get access to the Gentian cystatin GFR test?

Please see our ordering page to find a distributor in your areas or alternatively contact sales@gentian.no      

 

Our clinical test laboratory says that cystatin C tests are too expensive – is this true?

 This has been the case with existing tests. Gentian cystatin C test uses new production techniques and patented technology giving higher precision. The Gentian immunoassay is both better and cheaper than existing cystatin C tests.

 

Is the Gentian cystatin C test affordable? It’s still more expensive than the creatinine test – right?

It is a little more expensive than the creatinine test, but much less expensive than the creatinine clearance test which also involves 24 hours urine collection. And the total cost of a test is frequently more than the test alone. For example, the containers and work in a 24-hour urine collection cost far more than the Gentian cystatin C test itself! In addition there is minimal discomfort for the patient. The cystatin GFR does not involve any urine collection.

What do you mean by minimal patient invasion? You still have to take a blood sample – right?

Blood samples are an unavoidable part of patient investigation. The Gentian cystatin C analysis can be carried out on one routine blood sample, which can be done together with other standard tests in clinical analysers. Patients do not have to be invaded specifically for the Gentian cystatin C test; it’s just a tick-off on a standard blood analysis. More importantly, Gentian cystatin C can replace a range of unpleasant tests, including urine collection or radioactive measurements with repeated blood sampling. Especially for paediatricians, cystatin GFR is the preferred test method..

 

How does cystatin GFR compare to gold standards for precise determination of GFR?

Gold standard methods include the use of intravenous injections of radio labelled substances such as Cr-51-EDTA and Tc-99m-DTPA, or iodinated agents such as iohexol. GFR determined as cystatin C GFR shows a direct relationship between the reciprocal of cystatin C concentration in serum/plasma and GFR. Correlation is very good and is not hampered by collection errors or errors introduced by multiple measurements of blood or urine samples..

 

Relevant News

Gentian were inspected by FDA during 17-20th August 2015. The inspection was a success and was completed without any 483’s (non-conformances).

Read more

One of our own R&D scientists recently took part in a collaboration lead by Prof. Anders Grubb (University Hospital, Lund, Sweden) researching a simple, internationally applicable equation for calculating eGFR from any standardised cystatin C results. The paper, titled ‘Study cohort used to produce an international cystatin C-based estimating equation for GFR in adults and children’ is available online now.

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A published review on the incorporation of cystatin C into clinical practice