Infection Control & Hospital Epidemiology (2019), 40, 375–379 doi:10.1017/ice.2018.364
Concise Communication
Methods of estimating vancomycin use in an inpatient setting: days of therapy versus therapeutic drug monitoring–based exposure days Shutaro Murakami BSP1,2
, Junko Hiroi BSP1, Yasuharu Tokuda MD, MPH3, Ed Casabar PharmD4 and
Hitoshi Honda MD, PhD2 1Department of Pharmacy, Tokyo Metropolitan Tama Medical Center, Tokyo, Japan, 2Department of Infection Control, Tokyo Metropolitan Tama Medical Center, Tokyo, Japan, 3Muribushi Project for Teaching Hospitals, Okinawa, Japan and 4Department of Pharmacy, Barnes-Jewish Hospital, Washington University Medical Center St Louis, Missouri
Abstract
Underestimating antimicrobial use based on days of therapy (DOT) is recognized for certain antimicrobial agents.Weinvestigated the differ- ence betweenDOTand therapeutic drug monitoring (TDM)–based exposure days in estimating vancomycin use and demonstrated thatDOT may underestimate vancomycin exposure by ∼10%.
(Received 26 September 2018; accepted 21 December 2018)
Tracking antimicrobial consumption is vital for effective antimicro- bial stewardship. Days of therapy (DOT) is a measure commonly used in the United States to assess intravenous antimicrobial con- sumption in inpatient settings based on better applicability to the pediatric population and independence from antimicrobial dosage.1–3 However,DOT may be unsuitable for certain antimicro- bials because this method may underestimate their use, especially when intermittent doses are administered to elderly patients or those with impaired renal function. DOT measures antimicrobial administration but not antimicrobial exposure. Recently, the National Healthcare Safety Network (NHSN) antimicrobial use (AU) module began tracking antimicrobial use with a different denominator (ie, per 1,000 days present),2 but the optimal method has not been determined. Length of therapy (LOT) may be more effective for measuring
vancomycin use, especially in inpatients with impaired renal func- tion, because it reflects the actual days of exposure rather than the days of antimicrobial administration. LOT for intermittent antimi- crobial dosing is conventionally calculated as the number of days from the start to the end of antimicrobial administration compris- ing a single continuous treatment course.4 However, calculating the days of antimicrobial exposure with
intermittent dosing may be challenging. The study institution has been performing therapeutic drug monitoring (TDM) of vancomy- cin twice weekly since 2014 because once-weeklyTDMmay be inad- equate to detect a quick rise in trough concentrations exceeding the therapeutic range among hospitalized patients. Combining frequent TDM and measurements of vancomycin trough concen- trationsmay enable us to estimate vancomycin exposuremore accu- rately. The purpose of this study was to calculate TDM-based
Author for correspondence: Shutaro Murakami, Email:
shuutarou_murakami@tmhp.jp Cite this article: Murakami S, et al. (2019). Methods of estimating vancomycin use in an
inpatient setting: days of therapy versus therapeutic drug monitoring–based exposure days. Infection Control & Hospital Epidemiology, 40: 375–379,
https://doi.org/10.1017/ ice.2018.364
© 2019 by The Society for Healthcare Epidemiology of America. All rights reserved.
exposure days and tocompare the results withDOTfor vancomycin in a tertiary-care center.
Methods
This retrospective observational study used data collected from April 2012 to March 2018 at Tokyo Metropolitan Tama Medical Center, a tertiary-care center in Japan. During the study period, data on the monthly patient days, monthly intravenous vancomy- cin use, and frequency of TDM were collected. The DOT measurements were based on facility-wide, monthly
medication data. We counted only the day on which vancomycin was administered intravenously as a DOT, in accordance with the NHSNAU module definition.2 The TDM-based exposure days for facility-wide vancomycin use was measured as described below, based on TDM by a clinical pharmacist at the study institution. We determined the exposure days as the number of days from the start of vancomycin administration to the last day of vancomy- cin exposure as confirmed by twice weekly TDM. For TDM-based exposure days, the last exposure day was defined as either the last actual day of vancomycin administration or the last vancomycin trough concentration obtained on the planned final date of vanco- mycin therapy for an established infection requiring long-term antimicrobial therapy (eg, bloodstream infection). For patients without vancomycin TDM due to the short duration of their therapy (eg, as part of empiric therapy in the first 72 hours followed by prompt discontinuation or streamlining), the exposure days were counted as the days of exposure consisting of the number of days of actual vancomycin administration as with the measure- ment of DOT. At the study institution, clinical pharmacists per- form TDM for all patients on vancomycin to assist primary care providers in accordance with the vancomycin TDM guidelines.5 Moreover, the DOT data and the TDM-based exposure days were compared based on patients’ renal function. We stratified the monthly DOT and TDM-based exposure days into 4 groups
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132
