comparison of vancomycin calculation programs (therapeutic
TRANSCRIPT
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, BCPS1,2; Sergey Sarkisoff, PharmD1 1. Western University of Health Sciences, College of Pharmacy , Pomona, CA 2. West Hills Hospital and Medical Center, West Hills, CA
Abstract
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. 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. 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%). 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. 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 vancomycin-resistant 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
Acknowledgements
We would like to thank the pharmacy staff at WHHMC and Western University faculty members for their help and support with this project.
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.clinicalpharmacology-ip.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.
Methods
Discussion/Conclusion
•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.
•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) day-to-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 2-tailed TTEST.
Results
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.
Objective
105
Patients with “vancomycin per pharmacy” orders
between March 1st 2013- April 1st 2013
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
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
52
Patients excluded from data analysis
TDMS GlobalRph Clinical Pharmacology
Mean 13.3 14.1 18.7 18.8
Standard
Deviation5.24 3.22 7.10 7.73
0.33 <0.05 <0.05
95% CI ±3.67 ±3.89 ±5.16 ±5.18
P-value compared to Actual
Measured Trough
Actual Measured
Trough (mg/dL)
Predicted Trough (mg/dL)
TDMS GlobalRph Clinical Pharmacology
Mean -18.0% -57.6% -57.1%
Standard
Deviation43.17% 74.71% 74.58%
95% CI ±11.90% ±20.59% ±20.56%
Percent difference between measured and predicted trough
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