Comparison of Vancomycin Calculation Programs

Comparison of Vancomycin Calculation Programs (Therapeutic Drug
Monitoring System vs GlobalRph vs Clinical Pharmacology) in Predicting
Vancomycin Trough Levels at West Hills Hospital and Medical Center
Panit Taylor, PharmD,
1,2
BCPS ;
Sergey Sarkisoff,
1
PharmD
1. Western University of Health Sciences, College of Pharmacy , Pomona, CA 2. West Hills Hospital and Medical Center, West Hills, CA
Abstract
Results
Methods
Background: Vancomycin use has increased in the last decade due to emergence of
Methicillin-Resistant Staphylococcus Aureus (MRSA) infections. In clinical practice, it is
important to quickly achieve vancomycin therapeutic levels to inhibit and eradicate bacteria
growth. There are numerous vancomycin calculators for clinicians to use to predict
vancomycin trough; however, they yield different regimens. Among many calculators, West
Hills Hospital and Medical Center (WHHMC) pharmacists frequently use Therapeutic Drug
Monitoring System (TDMS), GlobalRph and Clinical Pharmacology. The objective of this
study is to evaluate and compare above mentioned calculators to actual measured
vancomycin troughs. Patient data are obtained and recorded. Results are compared and
analyzed to determine the most accurate calculator.
105
Patients with “vancomycin per pharmacy” orders
between March 1st 2013- April 1st 2013
Results: From March 1st 2013 to April 1st 2013, 105 patients received vancomycin dosed by
pharmacists, of which, 53 patients met the inclusion criteria. The means (±95% CI) of
measured troughs (13.3±3.67mg/dl) and predicted troughs for TDMS (14.1±3.89 mg/dl),
GlobalRph (18.7±5.16 mg/dl) and Clinical Pharmacology (18.8±5.18 mg/dl) were estimated.
P-values for difference between means of each of the 3 calculators and mean of the
measured trough were estimated (0.33,<0.05,<0.05). The mean percent differences
between predicted and measured troughs (±95% CI) were estimated for TDMS (-18.0
±11.90%), GlobalRph (-57.6±20.59%) and Clinical Pharmacology (-57.1±20.56%).
TDMS
GlobalRph
Clinical Pharmacology
•Inclusion Criteria: Adults (18 years of age and older) with intravenous vancomycin
dosed by pharmacists with creatinine clearance less than or equal to 30 mL/min
(using Cockcroft-Gault formula) and stable renal function (serum creatinine (SCr) dayto-day variations less than 30%)
•Exclusion Criteria:
• Patients with vancomycin dosed by physicians
• All patients under the age of 18 years
• Pregnant patients
• Patients with unstable renal function (SCr day-to-day variations greater than
30%)
• Patients with creatinine clearance below 30 mL/min (using Cockcroft-Gault
formula)
• Patients on dialysis
• Patients in Burn ICU unit
• Patients with initial vancomycin trough level not ordered at proper time
•Time period: 1 month 03/01/13 to 04/01/13
•Data Collection: Patients were identified from “vancomycin per pharmacy” orders
from March 1st of 2013 until April 1st of 2013 at WHHMC. Data was extracted from
the MediTech pharmacy system, PCIS and the patients’ charts. Variables for
collection included general demographic data (sex, height, and weight), patient
location, date of admission, indication for vancomycin therapy, dose, route,
frequency, serum creatinine, date, time and appropriateness of vancomycin trough
collection. Patients’ demographic information was then entered into TDMS, Clinical
Pharmacology and GlobalRph calculators and predicted trough levels were recorded
and compared to the actual measured levels. The mean % difference was estimated
with standard deviation utilizing Microsoft Excel software and analyzed for major
differences. For each calculator the means of predicted troughs were compared to
the mean of actual measured trough and analyzed for statistical difference using 2tailed TTEST.
-18.0%
-57.6%
-57.1%
Discussion/Conclusion
33
Patients meeting exclusion criteria
at time of order
• 8 on Hemodialysis
• 25 with CrCl < 30 mL/min
72
Patients meeting inclusion criteria
at time of order
Methods: This is an observational prospective study that derives reported vancomycin
trough levels from MediTech pharmacy system, PCIS and the patients’ charts. Extracted
levels are compared to levels predicted by the 3 calculators and analyzed for Mean percent
differences and Standard Deviation.
19
Patients excluded during time of
order
• 2 trough drawn at wrong time
• 17 discontinued before trough
levels drawn
53
Patients included in data analysis
Conclusion: The analyzed data indicates that TDMS is the most accurate vancomycin trough
calculator used at WHHMC. GlobalRph and Clinical Pharmacology calculators provided
almost identical results, but their estimates were not as accurate compared to TDMS. The
large confidence intervals indicate that further studies need to be performed with
significantly higher number of subjects needed for more accurate estimations.
52
Patients excluded from data analysis
Percent difference between measured and predicted trough
Mean
IRB approved for data collection and analysis on February 20th, 2013
Introduction
For many years since its initial use, vancomycin has traditionally been reserved as a drug of
"last resort", used only after treatment with other antibiotics had failed.1 One of the main
factors for such use of it was its complicated pharmacokinetic dosing. Compared to other
antibiotics, vancomycin has a narrow therapeutic range (10-20 mg/dL) while there is a
rather high risk of nephrotoxicity (usually with trough levels greater than 20 mg/dL). While
there are various formulas universally available for vancomycin dosing, the increased use of
it created an immediate need for faster, more accurate and less error-prone dosing. Thus,
various calculation software and programs were created for quicker and more accurate
dosing.2,3,4 Among these, the most frequently vancomycin calculation programs used by
WHHMC clinical pharmacists are TDMS Version 12.04.26 (created in 1986 by Healthware
Inc.), GlobalRph (launched in 1999 by David McAuley, PharmD with the vision of producing
practical and user-friendly software and tools for the busy clinicians) and Clinical
Pharmacology (used by more than 1,500 hospitals and over 35,000 retail pharmacies in the
United States, as well as government and managed care agencies, pharmaceutical
manufacturers and academic institutions).
Despite the fact that there are multiple vancomycin trough calculators available,
vancomycin dosing is still a challenge which contributes to emergence of vancomycinresistant organisms and vancomycin being increasingly displaced by newer antibiotics with
activity against MRSA (linezolid (Zyvox®), daptomycin (Cubicin®), quinupristin/dalfopristin
(Synercid®), ceftaroline (Teflaro®), and tigecycline(Tygacil®)).5
Objective
To estimate the mean difference in predicted vs. measured vancomycin trough using TDMS,
GlobalRph and Clinical Pharmacology vancomycin calculation programs and evaluate which
program provides more accurate estimates of vancomycin trough levels for the population
studied.
Standard
Deviation
43.17%
74.71%
74.58%
95% CI
±11.90%
±20.59%
±20.56%
Predicted Trough (mg/dL)
Actual Measured
Trough (mg/dL)
TDMS
GlobalRph
Clinical Pharmacology
Mean
13.3
14.1
18.7
18.8
Standard
Deviation
5.24
3.22
7.10
7.73
P-value compared to Actual
Measured Trough
0.33
<0.05
<0.05
±3.89
±5.16
±5.18
95% CI
±3.67
7300 Medical Center Drive, West Hills, CA 91307
panit.pollavith@hcahealthcare.com
phone (818) 676-4455; fax (818) 676-4242
References
1. Vandecasteele SJ, et al. The pharmacokinetics and pharmacodynamics of vancomycin in clinical
practice: evidence and uncertainties. J Antimicrob Chemother. 2012 Dec 18
2. GlobalRph Vancomycin/Aminoglycosides dosing calculator
http://globalrph.com/aminoglycosides.html
3. Therapeutic Drug Monitoring System (TMDS) 2000User Manual
http://www.tdms2000.com/site/p-downloads/TDMS%20Instructions.pdf
4. http://www.clinicalpharmacologyip.com/Forms/Resources/calculators.aspx?fl=fl2&cpnum=0&c=484
5. "Recommendations for Preventing the Spread of Vancomycin Resistance Recommendations of
the Hospital Infection Control Practices Advisory Committee (HICPAC)". MMWR Recomm Rep
44 (RR-12): 1–13. September 1995. PMID 7565541.
•Out of 105 patients started on “vancomycin per pharmacy” at WHHMC, 53 patients
were included in the results.
•The means (±95% CI) of measured troughs (13.3±3.67mg/dl) and TDMS(14.1±3.89),
GlobalRph(18.7±5.16) and Clinical Pharmacology (18.8±5.18) predicted troughs were
estimated. P-values for difference between means of each of the 3 calculators and
mean of the measured trough were estimated (0.33,<0.05,<0.05).
•The mean percent differences between predicted and measured troughs (±95% CI)
were estimated for TDMS (-18.0 ±11.90%), GlobalRph (-57.6±20.59%) and Clinical
Pharmacology (-57.1±20.56%)
Limitations:
•Since this is not a randomized controlled trial, it is difficult to evaluate clinical
outcomes
•Timing of levels drawn: timing of the actual blood draws for the levels depends on
laboratory and nursing staff
•Discontinuation of vancomycin orders by physicians: at least 17 more patients could
have qualified for the final data analysis
Conclusion:
The analyzed data indicates that TDMS is the most accurate vancomycin trough
calculator used at WHHMC. The TTEST revealed that there was no statistically
significant difference between the means for TDMS and actual measured troughs.
Even though GlobalRph and Clinical pharmacology calculated almost identical to each
other predicted troughs, their means were statistically different from the mean of
actual predicted troughs.
Acknowledgements
We would like to thank the pharmacy staff at WHHMC and Western University faculty
members for their help and support with this project.