Identifying the Care Gaps in Heparin-Induced Thrombocytopenia Testing Around the COVID-19 Pandemic

Introduction: Heparin induced-thrombocytopenia (HIT) is a severe autoimmune reaction to heparin that increases patients' risk of developing venous thrombosis, leading to fatal conditions such as pulmonary embolism. The clinical 4T scoring system guides need for further testing, based on noting fall in platelet counts, the timing of platelet counts falling in conjunction with heparin exposure, the presence of new thromboses, and ruling out other causes of thrombocytopenia. In patients in whom 4T scoring indicates a higher protest probability for HIT, screening is then performed. The Enzyme-Linked Immunosorbent Assay (ELISA) detects antibodies against platelet factor 4 (PF4)-heparin complexes. In order to confirm the diagnosis of HIT, the serotonin release assay testing is required, which refers to measuring the serotonin levels produced during platelet activation using radio-labeling techniques. Since the start of the COVID-19 Pandemic in 2020, there has been ongoing discussion regarding whether incidence of HIT diagnosis has increased. Herein we report on a retrospective observational study of a cohort of patients seen at a community hospital in Georgia between March 2017 to December 2022 to determine the changes in frequency of HIT and SRA testing, and to assess its association with the COVID-19 pandemic. Methods: We included patients aged >18 years, hospitalized at a community hospital in Georgia during the study duration and de-identified data was collected from electronic medical records. Text-based data analysis was performed to identify those patients who received HIT testing, SRA testing, and ultimately a final diagnosis of HIT (HIT positive and SRA positive). The overall rates of 4T scoring documentation and assessment in the hospital were also assessed. Several multivariable logistic regression models were constructed to examine factors associated with HIT testing and SRA testing, and their association since the start of the the COVID-19 pandemic (March 2020). Results: A total of 244,457 patients were included in the study population. Of them, 2,375 (0.97% of total) patients were tested with the HIT-ELISA, and only 468 (0.19% of total) patients were tested with SRA. In further subgroup analysis, evaluating the temporal associations of HIT and SRA testing, it was observed that the rate of HIT-ELISA testing increased since the onset of the COVID-19 pandemic, as did the rate of SRA testing (p < 0.000). Notably, of the 2,375 patients who received the HIT-ELISA testing, only 193 (8% of HIT-tested patients) had documentation of clinical suspicion of HIT with the 4T score. Discussion: An increase in HIT and SRA testing has been observed since the start of COVID-19 pandemic, with a notable lack of 4T score data in the study population preceding this testing. This study emphasizes the importance of clinician education regarding the process of accurate HIT diagnosis, which would start with clinical 4T scoring, followed by ELISA testing for screening, and finally confirmed by SRA testing. Further research is warranted to understand the barriers that may exist in providing guideline-directed evaluation of HIT so that targeted interventions can be implemented to ensure high-quality care is delivered to patients.