FAQ: Why is the cystatin C test perceived to be costly?

In this segment we are answering questions our Product Manager for cystatin C and our Product Specialist in the US receive about cystatin C and our cystatin C immunoassay at exhibitions, conferences, and client meetings. Today’s question is “Why is the cystatin C test perceived to be costly?”

Cystatin C as an adjunct to creatinine

The cost of cystatin C is often compared to the commonly used biomarker creatinine. Theodore Roosevelt famously said that “comparison is the thief of joy.” And while it is very unlikely that he meant for his words to be used in discussion of renal biomarker pricing, they may help explain the sentiment that cystatin C testing is costly, which is one of the reasons for the hesitation within health systems to order cystatin C, and therefore also one of the biggest barriers to making the test readily available to clinicians and patients.

Some major health systems in the US currently conduct between 400,000 and 500,000 creatinine tests annually at a cost between USD 0.20 and 0.50 per test. By contrast, the same health systems typically conduct less than a 1200 cystatin C tests per year. The underlying issue here is not that cystatin C testing is expensive, but that creatinine is so cheap that it could make even a reasonably priced test seem costly.

Comparing the price of cystatin C to a marker that has been discussed in medical literature for the better part of 135 years accomplishes little and may stand in the way of our ability to ensure equitable health outcomes.

Instead, cystatin C should be run together with creatinine as a confirmatory assessment of GFR or kidney function, as The NKF-ASN Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease recommends. The need to increase the use of cystatin C in combination with creatinine is documented in two recent studies published in the New England Journal of Medicine^1,2.

Costs go down as test volumes increase

Following publication of the NKF-ASN Taskforce recommendation to increase use of cystatin C as a confirmatory assessment of GFR, the Twitterverse erupted with comments on how increased use of the test would decrease its cost³. However, the notion that an increase in demand could decrease the price of test reagents seemed counterintuitive to most observers

Running 1 cystatin C sample per day will cost USD 75-100 in reagents, were as running an amount of for example 3000 test/month will bring the reagent price per test down to USD 5-10 based on the increased volume in the example above.

An inverse relationship exists between test volumes and reagent costs

The answer to why an inverse relationship exists between test volumes and reagent costs lies in how assays are performed on automated clinical chemistry analysers. The standard assay is composed of three components:

test reagents
quality control reagents
calibration reagents

Test reagents are used to measure the concentration of the analyte of interest in patient samples. Quality control materials are used at specific intervals to ensure that the analyser continues to generate consistent results throughout the day⁴. Calibration reagents are typically used once a month to fix the instrument’s readings to known values and to correct for subtle changes resulting from differences in ambient conditions and reagent lots⁴.

What should be noted here is that only the test reagent volume changes depending on the number of patient samples being tested. Running more samples allows the cost of the control and calibration reagents to be spread across a larger number of tests, bringing down the overall cost of the test. This illustrates why a health system performing a thousand cystatin C tests per year can expect to spend around USD15-25 per test on reagents whereas a hospital conducting 10,000 cystatin C tests per year would spend around USD 5-10 per test.

Cystatin C as a “send-out”

Of course, increasing the clinical utilisation of cystatin C comes with its own challenges. The low number of requests for cystatin C tests at most hospitals disincentives labs from dedicating the resources needed to incorporate it into their test catalogues. As a result, most health systems conduct the test as a “send-out.” Perhaps what is most concerning about outsourcing the test, however, is that limited competition among commercial labs has pushed the price range for a single cystatin C test to between USD 30 and as much as USD 200+ as seen on some hospital chargemasters.

In a recent webinar hosted by the American Kidney Fund*, Dr. Amy Karger revealed that only 7% of labs currently offer cystatin C testing in-house⁵. Being often a “send-out”, it is no surprise that another major grievance shared by clinicians who are eager to use cystatin C is that getting the results for a send out test takes too long.

Contact us for more information and ordering

Gentian’s turbidimetric cystatin C immunoassay has been validated on a wide range of clinical chemistry analysers.

FDA510(k) cleared and CE-marked
IVDR registration in progress
Developed and manufactured by Gentian
Manufactured according to ISO 13485:2016

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