Heparin Anti-Xa Assay

Vol. 19 • Issue 3 • Page 62
Case Study

eorgetown Hospital System (GHS) is a two-hospital system in Georgetown County between Myrtle Beach and Charleston, SC. The organization, founded in 1950, includes approximately 300 inpatient beds, including the area’s only acute rehab unit. Numerous outpatient rehabilitation clinics, two pain management centers, a wound healing center and a cancer treatment center in locations throughout the GHS service area are also part of the organization.

GHS has joined an increasing number of large and small hospitals across the country that have implemented new protocols using the Heparin Anti-Xa Assay for monitoring patients on unfractionated heparin therapy. For GHS, the use of Heparin Anti-Xa assay constituted a dramatic change in the way heparin therapy is monitored.

A Change

When the heparin assay technology became more widely available and began to be marketed to facilities similar to GHS, the organization’s laboratory administration approached pharmacy officials to investigate the feasibility of using Anti-Xa as a monitoring option rather than activated partial thromboplastin time (aPTT) for patients on unfractionated heparin. Despite the fact that at the time some hospitals in surrounding states had just made the conversion, GHS opted to delay implementation due to the relative infancy of this new technology.

In 2008, the Joint Commission standards mandated that all hospitals develop and/or revise anticoagulation protocols to comply with the NPSG 3E. These standards focused on reducing the likelihood of patient harm that is associated with use of anticoagulation therapy. During the revision process, a GHS pharmacist, who was residency trained at a North Carolina hospital that had already made the transition, suggested that GHS follow suit and implement use of Heparin Anti-Xa levels to monitor heparin therapy. This recommendation embodied the basic tenets of GHS’ overall mission and vision, which is focused on providing quality healthcare services to the community using the best practices available.

In late 2008, GHS conducted a feasibility investigation on use of Anti-Xa as a monitoring option rather than aPTT for patients on unfractionated heparin. Based on results of the study, heparin assay monitoring was determined to be a more reliable test that improves outcomes, lowers morbidity and shortens lengths of stay. Armed with this knowledge, pharmacy and laboratory administrators prepared a proposal for change to heparin anti-Xa assay monitoring, and presented the plan to the Pharmacy and Therapeutics (P&T) committee. The P&T committee acknowledged that the heparin assay monitoring was more costly; however, the benefit of safer and more accurate monitoring outweighed this isolated cost.

In fall 2009, GHS’ laboratories began planning to upgrade existing equipment with Diagnostica Stago‘s STA Compact® to perform heparin Anti-Xa assays in-house. Not only would this allow the organization to use the test as a day-to-day method to monitor heparin patients, but it would also provide a new service of real-time monitoring in underweight, overweight and pregnant patient populations.


In-service training sessions were conducted with laboratory, nursing and pharmacy personnel on the planned change. The week prior to implementation, handouts describing the advantages and disadvantages of aPTT and Heparin Anti-Xa assays were distributed to nurses and physicians.

Pharmacy and the lab met on several occasions to decide how the new test would be reported from lab. The Clinical IS department was crucial in building and mapping the new lab test in the hospital’s electronic medical record. Educating the staff and physicians on the benefits of this new technology proved instrumental in a smooth transition. After much collaboration by an interdisciplinary team consisting of pharmacy, lab, nursing, information systems (IS), hospital administrators and physicians, conversion to Heparin Anti-Xa assays was completed in December 2009.

In the first month, anecdotal evidence suggests that GHS patients on heparin infusion have had fewer rate changes, and fewer heparin assays were above the therapeutic range than with aPTT monitoring. Lab has also noted that nursing is not discontinuing the heparin assay when the heparin drip is discontinued. They were able to make this observation because the heparin assay result value was <0.1. It is believed that this was happening with aPTTs as well, but because the aPTTs were normal range, it was not recognized as an indicative result.

Soon, GHS plans to conduct a drug utilization evaluation for heparin to validate the hypothesis that using Heparin assays in place of aPTT levels results in quicker time to goal anticoagulation, fewer testing/lab draws and fewer dosage changes. The ultimate goal is to provide patients the best medical care by lowering risk for bleeding and thrombus recurrence and decreasing length of stay, thus improving patient outcome.

Dr. Willm is assistant director of Pharmacy, Waccamaw Community Hospital, Murrells Inlet, SC, part of the Georgetown (SC) Hospital System.

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