Implementation of Electronic Alerts to Improve Clinician Management of Heparin Induced Thrombocytopenia

Introduction: Heparin induced thrombocytopenia (HIT) is often a difficult clinicopathologic diagnosis to make, which can result in poor patient outcomes due to delays in identification and treatment. Platelet factor 4 (PF4) antibody ELISA tests are routinely used to diagnose HIT. PF4 ELISAs have high sensitivity but low specificity; therefore, to guide appropriate ordering of PF4 tests ASH guidelines recommend calculating a 4T score to assess the pre-test probability, but this is not always done. We implemented and studied the impact of three electronic health record (EHR) based strategies to improve diagnosis and treatment of HIT at our institution.

Methods: At Brigham and Women's Hospital, we created 1. an interruptive alert to recommend discontinuation of active heparin products when signing a PF4 order (Figure 1), 2. integrated 4T score calculations with PF4 test ordering, and 3. through randomization, investigation of the efficacy of an interruptive alert advising clinicians not to order the PF4 test if the 4T score was low.

Pre and post implementation groups for each intervention were identified and compared. The heparin discontinuation alert went live on December 20, 2018; the pre-intervention group included patients with PF4 tests in the previous 12 months, and the post-intervention group for 12 months following.

The 4T score elements were integrated into the PF4 ELISA order on August 31, 2020; the pre-intervention group included patients with PF4 tests ordered 9 months prior and the post-intervention for 9 months following. In the pre-intervention group, we performed chart review to assess whether the ordering provider documented a 4T score; if a 4T score was not documented in the EHR, it was calculated retrospectively by the research team. Groups were compared to determine the proportion of appropriate PF4 orders (4T score > 3), and the efficacy of the randomized alert recommending no PF4 ordering if the 4T score was < 4. For both alert-based interventions, Chi-squared analysis was performed to determine statistical significance between defined groups.

Results: 1. Heparin discontinuation: For the heparin discontinuation alert analysis, of 781 orders for PF4 tests in the pre-heparin discontinuation alert group, 293 eligible orders were used, and of 708 orders in the post-alert group, 235 orders were included. Eligible orders were those that had heparin ordered at the time of PF4 testing and those that were not cancelled. Implementation of the heparin discontinuation alert increased heparin discontinuation from 35% to 46 % (p = 0.015) (Figure 2).

2. 4T Score Documentation and Associated PF4 Appropriateness: Of the patient charts reviewed prior to integration of the 4T score elements into the PF4 order, only 31% (85/272) had a 4T score documented in the EHR. Of the 547 patients post-intervention, by design 100% had a documented 4T score. In the pre-intervention group, of those with calculated 4T scores before PF4 test ordering, 69.4% (59/85) were appropriate, while for those without a 4T score calculated just 27.2% (51/187) were appropriate based on retrospective 4T calculation, for a composite 40.4% appropriate pre-intervention PF4 test ordering, as compared to 79.1% (246/311) appropriate PF4 test ordering post-intervention (p <0.00001). Subspecialties with the highest inappropriate ordering of PF4 tests were: Surgical ICU (32.3%), Oncology (25.6%), the Cardiac Critical Care Unit (24.5%), and Adult Medicine (23.8%).

3. Alert to Not Order PF4 With Low 4T Score: Rates of appropriate PF4 ordering were similar between the group randomized to see the interruptive alert advising clinicians not to order the PF4 test if the 4T score <4 (242 appropriate orders/ 298 completed orders, 81%) and the control group that did not see the alert (306 appropriate orders/ 402 completed orders, 76%; p=0.13).

Conclusions: Heparin product continuation can be life-threatening in patients with HIT. Implementation of electronic decision support significantly increased discontinuation of heparin products in patients in whom HIT was suspected. Forced calculation of the 4T score resulted in increased appropriateness of PF4 test orders by 40%. The impact of randomized guidance not to order a PF4 test when the 4T score was low was not as successful. Overall, the EHR interventions resulted in improved patient care for those suspected of having HIT at our institution.

Zon:Amagma Therapeutics: Consultancy, Current equity holder in private company. Rubins:Statera: Consultancy. Grandoni:Pfizer: Membership on an entity's Board of Directors or advisory committees. Connors:CSL Behring: Research Funding; Abbott: Consultancy, Membership on an entity's Board of Directors or advisory committees; Alnylam: Consultancy; Bristol Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Honoraria, Speakers Bureau; Anthos: Membership on an entity's Board of Directors or advisory committees; Werfen: Membership on an entity's Board of Directors or advisory committees.