ORLANDO – Thromboprophylaxis for 3 weeks after discharge following abdominal surgery is more cost effective than is inpatient thromboprophylaxis alone, given certain base case assumptions, according to a decision tree analysis.
The findings, which incorporate both cost- and patient-related factors, provide clarity for clinicians about when extended duration thromboprophylaxis is appropriate, Dr. James C. Iannuzzi said at the annual Digestive Disease Week.
The analysis indicates that extended-duration thromboprophylaxis with low-molecular-weight heparin for 3 weeks after discharge is preferable to 7 days of inpatient-only thromboprophylaxis in cases where venous thromboembolism (VTE) risk is estimated at 0.88% to 2.39%; patient preferences regarding costs and medication administration, including the need for self-administered injection of low-molecular-weight heparin (LMWH), should be considered in these cases, said Dr. Iannuzzi of surgical health outcomes and research enterprise at the University of Rochester (N.Y.) Medical Center.
Extended-duration thromboprophylaxis dominates in cases in which the estimated VTE risk exceeds 2.39%, he said.
"Current guidelines are inconsistent about what metrics should be used, which makes it difficult for providers to decide whether extended-duration thromboprophylaxis would be beneficial. This likely plays a significant role in the current lack of adherence to guidelines," he said in an interview, adding. "This study was really aimed at providing clinicians a better cut-off for when it should be used, incorporating both the cost and patient perspective."
To assess cost effectiveness of thromboprophylaxis, Dr. Iannuzzi and his colleagues compared extended-duration treatment for 21 days after discharge (following 7 days of inpatient prophylaxis) with inpatient prophylaxis alone in a hypothetical case involving abdominal oncologic resection without complications in an otherwise healthy 45-year-old male patient.
Willingness to pay was set at $50,000 per quality-adjusted life-year (QALY), and the probabilities of various factors and scenarios were determined based on the available literature – much of it coming from the orthopedic literature. Costs were in U.S. 2013 dollars adjusted using the consumer price index; effectiveness was based on QALY (utility considered over 1 year), and cost effectiveness was evaluated using an incremental cost-effectiveness ratio, Dr. Iannuzzi explained.
Sensitivity analyses were performed to assess uncertainty within the model, with particular interest in the threshold for cost effectiveness based on VTE incidence, he said.
The endpoints were pulmonary embolism or deep vein thrombosis with attendant costs and assigned effectiveness evaluated by QALY, he said.
Based on the predetermined probabilities, and assuming an annualized cost of $23,248 for pulmonary embolism, $21,540 for deep vein thrombosis, $14,363 for post-thrombotic syndrome, $706 for generic LMWH, and $872 for brand-name LMWH, the threshold for the relative cost effectiveness of extended-duration thromboprophylaxis was VTE probability of 1.65% for brand-name LMWH, and 0.88% for generic LMWH.
"The 0.88% threshold is near the range of most major abdominal surgeries, which highlights the importance of using extended-duration thromboprophylaxis. However, the model was sensitive to changes in medication costs and patient values until postdischarge VTE risk exceeded 2.4%," Dr. Iannuzzi explained, adding that the model sensitivity in the 0.88% to 2.39% range is the reason why it is important to consider the patient perspective and the availability of generic LWMH in such cases.
He and his colleagues recently developed a risk score to help with postdischarge VTE prediction and to guide decision-making. The risk score, published online in May in the Journal of Vascular Surgery (J. Vasc. Surg. 2013 [doi:10.106/j.jvs.2012.12.073]), considers patient, operative, and early outcome factors to identify patients at increased risk.
The current findings, which pave the way for patient-centered decision making, use cost effectiveness of extended-duration thromboprophylaxis as a measure for risk, and should inform future guidelines’ definition of high risk. They also suggest that while a blanket approach to prophylaxis is not warranted, payers should cover the cost of extended-duration treatment.
"When cost was analyzed alone – without taking patient discomfort and the burden of self-injections into account, the threshold for cost effectiveness was much lower, suggesting that from the payer perspective, significant cost savings would be derived by increasing extended-duration thromboprophylaxis use," he explained.
Dr. Iannuzzi reported having no disclosures.