Predictors of in-Hospital Mortality in Thrombotic Thrombocytopenic Purpura in Adults in the United States: A Population Analysis Using the NIS Database

Introduction: Thrombotic Thrombocytopenic Purpura (TTP) is a rare but life-threatening disorder. Understanding the predictors of in-hospital mortality for TTP patients can help improve management and outcomes. This study aims to identify the risk factors associated with increased mortality among hospitalized TTP patients using the National Inpatient Sample (NIS) database. Methods: This study utilized the NIS database from 2016 to 2020 to analyze the predictors of in-hospital mortality in TTP patients. Adult patients aged 18 or older with a diagnosis of TTP (ICD-10 DC M31.1) who underwent plasmapheresis (ICD-10 PC 6A550Z3, 6A551Z3) were identified. Demographic variables were analyzed using chi-square tests. To evaluate the risk factors associated with in-hospital mortality, we considered several key variables. These factors were selected due to their prevalence and known impact on TTP patient outcomes.. Multivariate logistic regression was employed to calculate adjusted odds ratios (aOR) for in-hospital mortality, controlling for these variables. All analyses were conducted using STATA 18.0. Results: A total of 1783 TTP patients who underwent plasmapheresis were identified. The median age was 50 years (IQR = 26 years), and females comprised 67.36% of the cohort. The majority were White (42.37%) and Black patients (41.50%). Most patients were treated at teaching hospitals (88.01%). The inpatient mortality rate of patients with TTP treated with plasmapheresis was 8.47% (n=157). Linear regression analysis of mortality trends over the five-year period showed a non-significant increase in mortality rates (coefficient 0.0033, p=0.543), indicating no substantial change in in-hospital mortality among TTP patients undergoing plasmapheresis from 2016 to 2020. Patients aged ≥45 years had a higher mortality rate (aOR 1.71, p=0.048). Black patients had significantly lower odds of in-hospital mortality compared to White patients (OR = 0.58, p=0.030). There was no statistically significant difference in mortality among other races compared to White patients. Using multivariate logistic regression, patients with heart failure (aOR 2.68, p<0.001), acute kidney injury (aOR 2.78, p<0.01), severe sepsis (aOR 6.04, p<0.01), and cerebrovascular disease (aOR 1.96, p<0.045) had higher odds of in-hospital mortality. Other factors like pregnancy, hypertension, obesity, diabetes, chronic kidney disease, HIV, viral hepatitis, systemic lupus erythematosus, stem cell or solid organ transplant, chronic obstructive pulmonary disease, and acute myocardial infarction were not significant predictors. Conclusion: TTP admissions were more common in females and among White and Black patients, with a median age of diagnosis of 50 years. Black patients disproportionately accounted for 41.5% of TTP admissions for plasmapheresis despite representing only 13.7% of the US population. It is unclear whether this is due to a higher incidence of TTP or a higher likelihood of relapse, warranting further study. Factors associated with increased in-hospital mortality included increasing age (≥45 years), heart failure, acute kidney injury, severe sepsis, and cerebrovascular disease. Black patients had lower odds of inpatient mortality compared to White patients. The analysis of mortality trends from 2016 to 2020 showed no significant linear trend, indicating stable mortality rates over these years. Further studies should be conducted to explore these racial disparities and implement targeted interventions to improve outcomes in high-risk patients.