Category: Professional Posters
Purpose: Heparin induced thrombocytopenia (HIT) is a clinical diagnosis which can be validated by a pre-test probability scoring system like the 4T’s score and laboratory testing. A historical review demonstrated high rates of platelet factor 4 (PF4) testing with limited serotonin release assay (SRA) testing. The study determined that 4T scores of 4 or greater and a new thrombotic event, regardless of 4T score, were independent risk factors for HIT. The purpose of this study is to assess the impact of the development of a diagnostic algorithm for HIT on PF4 testing and subsequent treatment in these patients.
Methods: This was a single-center, IRB-exempt, prospective chart review of hospitalized patients between January 1, 2019 and April 30, 2019 with a positive PF4 enzyme linked immunosorbent assay (ELISA) immunoassay test result. Historical study data from a previous retrospective study reviewing patients with a positive PF4 ELISA immunoassay test and subsequent treatment with argatroban was utilized as a comparator for outcome measures.
Rates of PF4 ELISA immunoassay and SRA functional assay confirmation testing were reviewed and treatment with argatroban in these patients was evaluated. Median optical density value, SRA result, number of days on argatroban therapy and associated adverse drug were also recorded. The data was assessed to determine the impact of a diagnostic algorithm for HIT. Descriptive and comparative statistics were utilized in the data analysis.
Results: Evaluation of historical data from a previous retrospective chart review led to the implementation of a diagnostic algorithm for HIT. Overall, the implementation of the diagnostic algorithm led to a significant decrease in the ordering of PF4 ELISA immunoassays and an increase in SRA confirmatory testing. Post implementation of the HIT diagnostic algorithm, PF4 testing decreased by 43% with monthly PF4 orders decreasing from 71 to 40 during the 4-month study period. Meanwhile, SRA testing increased by 71%. A total of 24 SRA functional assays were ordered, with 68% of the positive PF4 results being reflexed to SRA functional assay orders. Also, argatroban use decreased from 12 to 9 patients per month; on the other hand, the length of therapy and argatroban utilization ratio per positive PF4 increased. This can likely be attributed to the optimal patient selection for HIT diagnosis and management in the post diagnostic algorithm implementation group.
Conclusion: Implementation of a diagnostic algorithm for HIT that includes 4T score calculation, PF4 ELISA immunoassay testing, and SRA functional assay confirmation testing had a significant impact on the rate of diagnostic testing for HIT at our institution. Implementation of the diagnostic algorithm has led to a decrease in the over testing and subsequent over diagnosis of HIT.