|89th Annual Meeting Abstracts
Flap Complications and Thrombophilia: A Model Using Incremental Cost Effective Analysis for Preoperative Screening
Kendra G. Bowman, MD, PhD, Matthew Carty, MD.
Brigham and Women's Hospital, Boston, MA, USA.
Purpose: Free flap complications are expensive, morbid and psychologically stressful for the patient. Thrombosis represents the greatest risk for flap complications and leads to reoperation, anticoagulation, and in some cases, flap necrosis and loss. Flap thrombosis is usually attributed to mechanical factors rather than an inherited or acquired predisposition to clot formation. However, approximately 10% of the population has one or more of the known thrombophilias, and the role of these in spontaneous thromboembolic events such as venous thromboembolism (VTE) and arterial thromboses are well established. In addition, patients undergoing free tissue transfer often have comorbidities associated with acquired hypercoagulability, such as malignancy or trauma. We posit that thrombogenic conditions in the setting of surgery, coupled with acquired hypercoagulability, underlie a greater proportion of flap failures than is currently recognized. Preoperative screening and intervention for thrombophilias may be cost effective and warrant a cost analysis.
Methods: We developed a cost effective analysis using an incremental cost effective ratio (ICER) model. This analysis is based upon the reported prevalence of eight common thrombophilias, our own rate of flap thrombosis across 265 cases, and the corresponding cost of these complications. As a proxy for the relative risk of thrombosis for patients with thrombophilia, we used the reported relative risks for spontaneous venous thromboembolism and arterial thrombosis in the general and thrombophiliac populations. We calculated the cost of a thrombophilia screen at our institution and reviewed medical records to ascertain the incremental cost of flap complications. Using these data, we developed a dynamic analysis ICER model to evaluate several scenarios based upon the cost of screening, our flap complication rate and complication cost.
Results: We reviewed 265 free flaps at our institution performed over a five year period. Thrombosis related complications occurred in 13 (4.9%) of flaps, leading to five flap failures (1.9%). The incremental cost of flap failure over an uncomplicated flap was an average of $30,000 per flap (range $10,000 to $80,000). We found that the expense of a complete preoperative thrombophilia screen is cost effective when a flap complication exceeds an incremental cost increase of approximately $57,000. Using a limited preoperative thrombophilia screen that captures 90% of the anticipated thrombotic complications, our model estimates that screening is cost effective when a related flap complication exceeds an incremental cost increase of $42,500.
Conclusions: Flap complications cost an average of $30,000 with a range of $10,000 to $80,000. An evidence-based analysis using an ICER model demonstrates that thrombophilia screening is a cost-effective measure when the anticipated incremental cost of a thrombotic free flap complication is greater than approximately $42,000 to $57,000. Preoperative thrombophilia screening is a defensible strategy for the prevention of complications, and this model provides a rational guide for cost effectiveness analysis. Clinical studies on the contribution of specific thrombophilias to free flap thrombosis are warranted.