Incidence of ITP before and after COVID-19: A Nationwide Inpatient Sample Study

Background/Purpose: Since the onset of the coronavirus disease-2019 (COVID-19) pandemic in December 2019, the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been postulated as a potential trigger for numerous autoimmune disorders. Specifically, immune thrombocytopenia (ITP) has been reported following SARS-CoV-2 infection and vaccination. In this study, our objective was to compare the incidence of ITP in the pre- and post-COVID eras. Methods: The Healthcare Cost and Utilization Project National Inpatient Sample (HCUP-NIS) database were queried to identify admissions for ITP in 2018 and 2020, using ICD-10 codes for a primary diagnosis of ITP. The primary outcomes analyzed included mortality, length of stay (LOS), and total hospital charges (THC). Secondary outcomes encompassed acute kidney injury (AKI), intensive care unit (ICU) admission, and the need for blood transfusion. Statistical analyses were performed using t-tests, univariate and multivariate logistic regression analysis in Stata. Results: A total of 22,840 ITP patients were admitted in our study group, comprising 12,160 in 2018 and 10,680 in 2020 (53.2% and 46.7%, respectively). No significant differences were observed in patient sex (43% males and 56.8% females, P = 0.74), mean age (56.4 in 2018 and 55.8 in 2020), or race, except for a higher incidence among Native Americans in 2020 (0.2% vs. 0.6%, P = 0.004). There were no significant differences in medium household income, insurance, bed size, location/teaching status, and the region of the hospital. In primary outcomes, total deaths in the main group numbered 264 (1.16%), with non-significantly higher mortality in 2020 (1.36% vs. 0.99%, OR 1.37, P = 0.24). Females had significantly lower odds of mortality (OR 0.46, P = 0.007, CI 0.26-0.80). Regarding secondary outcomes, there was no significant difference in the length of hospital stay. The incidence of AKI was non-significantly higher in 2020 (9.6% vs. 7.9%, P = 0.054) with a high need for ICU admission (1.1% vs. 0.7%, OR = 1.6, P = 0.14) and no significant need for blood transfusion. Conclusion: Despite multiple reported cases of ITP triggered by the virus and vaccines during the COVID-19 pandemic, our study did not reveal a significant increase in ITP cases in 2020 compared to 2018. Further studies are warranted to confirm the causality between COVID-19 and ITP, including analyses of incidence in years after 2020, considering the initiation of vaccinations at the end of that year.