Cystatin C - a helpful tool for accurate drug dosing

Cystatin C based eGFR when prescribing drugs 

A lot of drugs, especially antibiotics and cytotoxic drugs such as vancomycin, carboplatin, digoxin, are metabolised and excreted through the kidneys. When prescribing pharmaceuticals that have a narrow therapeutic window, it becomes exceedingly important to have an accurate understanding of the patients' Glomerular Filtration Rate (GFR), which measures the rate water and dissolved substances are filtered out of the blood per unit time.

Why is accurate dosing so important?

• Prescribing too low a dose is associated with lack of efficacy and sub-optimal treatment
• Too high a dose can put the patient at risk for severe side effects
• Nephrotoxicity impacts on length of stay

Vancomycin: importance of correct dosing

The antibiotic drug, vancomycin is an example of a drug that has a narrow therapeutic window, and therefore thorough level monitoring is recommended [1-2]. Too low trough concentrations are associated with both clinical failure and significantly increased risk of resistance. In the other direction, too high concentrations will predict both nephrotoxicity and ototoxicity [3-5]. Cystatin C correlates closely with the mGFR, and cystatin C testing can therefore improve patient treatment. Correct  dosing will also create cost savings, due to more effective treatment and shorter recovery time.

Cystatin C, drug dosing and effective patient treatment

Monitoring patient's cystatin C levels can improve patient treatment and shorten the recovery time. Correct dosing can therefore create cost savings, due to more effective treatment.

Want to learn how a hospital network in the US managed to save cost on and shorten length of stay by introducing cystatin C testing as part of vancomycin dosing and treatment. Contact our Product Manager for Cystatin C today:

Gentian Cystatin C Immunoassay advantages

• The Gentian Cystatin C Immunoassay (ERM-DA471/IFCC standardised) is an in vitro diagnostic test for quantitative determination of cystatin C in human serum and plasma

• FDA510 (k) cleared and CE-marked

• Particle-Enhanced Turbidimetric Immunoassay (PETIA)

• Available for a wide range of clinical chemistry analysers with documented high inter-instrument accuracy [6]

• Avian antibodies - Avoids interference with rheumatoid factor [7]

References:

1. Liu C et al. Clinical practice guidelines by the infectious diseases society of America for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children: executive summary. Clin Infect Dis 2011, 52:285–292.
2. Rybak M et al. Therapeutic monitoring of vancomycin in adult patients: a consensus review of the American Society of Health-System Pharmacists, the Infectious Disease Society of America, and the Society of Infectious Diseases Pharmacists. Am J Health Syst Pharm 2009, 66:82–98.
3. Kullar R et al. Effects of targeting higher vancomycin trough levels on clinical outcomes and costs in a matched patient cohort. Pharmacotherapy. 2012;32:195-201.
4. Charles PGP et al. Clinical features associated with bacteremia due to heterogeneous vancomycin-intermediate Staphylococcus aureus. Clin Infect Dis. 2004;38:448-451.
5. Forouzesh A et al. Vancomycin ototoxicity: a reevaluation in an era of increasing doses. Antimicrob Agents Chemother. 2009;53:483-486.
6. Eckfeldt JH et al. Arch Pathol Lab Med 2015;139:888-93.
7. Larsson A et al. J Immunol Methods. 1988 Apr 6;108(1-2):205-8.