Impact of Race on the Mortality of Thrombotic Thrombocytopenic Purpura in the United States: A Population Study

Introduction

Thrombotic Thrombocytopenia Purpura (TTP) is a rare and life-threatening thrombotic microangiopathy characterized by severe thrombocytopenia, microangiopathic hemolytic anemia, ischemic organ injury especially kidneys, brain, heart due to microvascular thrombosis. There is limited data reporting predictors of survival in TTP. Therefore we sought to evaluate the impact of race as well as other risk factors on the incidence of mortality due to TTP.

Methodology

The National Inpatient Sample database for the year 2017 was queried for the data. We identified all hospital admissions with TTP as the primary diagnosis using the International Classification of Diseases (ICD-10) code. We studied the characteristics of all TTP hospitalizations and depicted the epidemiological factors associated with the in-hospital mortality of TTP. Logistic regression analysis was used to identify the predictors associated with mortality. Univariate and multivariate analysis were performed. The data were analyzed with STATA/IC 16.0 version.

Results

A total of 390 hospitalizations of TTP as a primary diagnosis were identified. The mean age of admission was 48 +/- 0.86. Predominant population was females compared to males (61% vs 39%, n= 238 vs 152). Rest of the baseline characteristics are described in table 1. In-hospital mortality rate was 8.2% (n=32). The mortality rate of males was higher compared to females but was not statistically significant (9.2% vs 7.6%, p= 0.45). African Americans (AA) with TTP admissions had significantly higher odds of dying in the hospital compared to Caucasians with TTP admissions (adjusted odds ratio (aOR) = 3.2, p= 0.012, 95% CI = 1.3- 4.8). 80% (n=312) of the patients received plasmapheresis. Those who received plasmapheresis had 40% less odds of dying than those who did not have plasmapheresis (aOR= 0.60, p <0.001, 95% CI = 0.013-0.26). On multivariate analysis, elderly patients (age >=75) had higher mortality compared to younger patients (aOR= 5.6, p= 0.013, 95% CI = 2.4- 7.8). The mortality rate of elderly patients was 37.5% and that of younger patients was 6.28% (p <0.001). Also, patients who had public insurance (Medicare + Medicaid) had higher mortality compared to those with private insurance (aOR= 2.4, p = 0.034, 95% CI = 1.8-3.7). AA had higher public insurance (52.2% vs 47.2%) and self-paying status (10% vs 6%) compared to other races (p= 0.007). Admission during weekends vs weekdays, geographical regions of hospitalizations, admissions to teaching vs non-teaching hospitals, and rural vs urban hospitals did not carry a statistically significant difference in terms of mortality rates. The differences in the mortality outcomes persisted after adjusting for confounding factors including co-morbidities. Sepsis, acute kidney injury (AKI), and hypertension were found to be independent predictive factors for mortality in patients admitted with TTP (Table 2). AA was found to have significantly higher odds of developing AKI (aOR= 1.21, 95% CI = 1.1- 2.3, p= 0.03) and hypertension (aOR= 1.1, 95% CI= 1.02- 3.4, p= 0.045) and there were no significant differences observed in other risk factors such as sepsis, malignancy, smoking, diabetes and encephalopathy between AA and other races.

Conclusion

AA ethnicity, elderly patients, no plasmapheresis, public insurance, sepsis, AKI, and hypertension were found to be the factors associated with higher mortality in patients admitted with TTP. AA had higher odds of developing AKI and hypertension which could be some of the reasons for their inferior survival. Early identification of high-risk population and prompt treatment is needed to improve survival outcomes. Further research is required to study the underlying reasons for the higher mortality rates of AA with TTP.

Przespolewski:Jazz Pharmaceuticals: Research Funding; ALX Oncology: Other: Site Principal Investigator; Merck: Other: Site Principal Investigator.