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Content Update

July 12, 2017

Using Cystatin C to Guide Vancomycin Dosing: Cystatin C is a renal biomarker that has been proposed to be used as an alternative to or in conjunction with creatinine for estimating glomerular filtration rate (GFR). Two recent studies employed a practical approach to development and implementation of a cystatin C-inclusive vancomycin dosing nomogram in clinical practice. The authors developed a dosing nomogram that used CKD-EPIcreatinine-cystatinC based estimated GFR (eGFRcr-cysC) as well as the target vancomycin trough level and patient weight. The authors then conducted a QI project to evaluate the routine use of this nomogram in critically-ill patients. Use of the CKD-EPIcreatinine-cystatinC equation to estimate GFR for vancomycin dosing was shown to be feasible and was associated with a clinically and statistically significant increase in target vancomycin trough achievement. Additional prospective research is warranted.



  • image Understanding the difference between normal host flora and typical pathogens will help to determine whether a patient is truly infected or merely colonized.

  • image Direct examination of tissue and body fluids by Gram stain provides rapid information about the causative pathogen.

  • image Isolation of the offending organism by culture or rapid diagnostic testing assists in the diagnosis of infection and allows for more definitive directed treatment.

  • image Development of molecular testing systems (or rapid diagnostic testing) has improved our ability to diagnose infection and determine the antimicrobial susceptibilities for numerous pathogens, including fastidious or slow growing mycobacteria and viruses.

  • image Although highly standardized, in vitro antimicrobial susceptibility testing has limitations and often cannot truly mimic the conditions found at the site of an infection. This can cause discordance between in vitro susceptibility results and in vivo response to therapy.

  • image Laboratory evaluation of antimicrobial activity is an important component of the pharmacotherapeutic management of infectious diseases.

  • image When used appropriately, rapid automated susceptibility test systems appear to improve therapeutic outcomes of patients with infection, especially when they are linked with other clinical information systems.

  • image Laboratory tests such as the minimum inhibitory and minimum bactericidal concentration tests, time-kill tests, postantibiotic effect tests, and antimicrobial combination testing are important for the clinician to understand because they help to determine antimicrobial pharmacodynamic properties.

  • image Routine monitoring of serum concentrations is currently used for a select few antimicrobials (eg, aminoglycosides and vancomycin) in an attempt to minimize toxicity and maximize efficacy.

  • image Appropriate timing for the collection of serum samples when measuring antimicrobial serum concentrations is crucial to ensure that proper data are generated on the pharmacokinetics of antimicrobials.

  • image Monitoring of aminoglycoside serum concentrations and the use of extended-interval doses can help to maximize the probability of therapeutic success and minimize the probability of aminoglycoside-related toxicity for certain infections.

  • image Vancomycin and aminoglycoside serum concentration monitoring should be routinely done to ensure adequate serum concentrations, minimize toxicity, and avoid the potential for resistance.

  • image Antimicrobial pharmacodynamics have become a crucial consideration for the selection of both empirical and pathogen-directed therapy in the current era of antimicrobial resistance.


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