Trends and Disparities in Idiopathic Thrombocytopenic Purpura-Related Mortality in the United States: A Retrospective Study over Two Decades

Introduction: Idiopathic thrombocytopenic purpura (ITP) is an autoimmune disorder characterized by a low platelet count and an increased risk of bleeding in the absence of another cause. It is caused due to the production of antibodies against platelet surface antigens. ITP is associated with several complications including intracerebral hemorrhage, and thus it becomes essential to determine trends and disparities in mortality of patients with ITP to identify vulnerable populations.

Methods: We extracted mortality data from the CDC Wide-ranging ONline Data for Epidemiologic Research (WONDER) database from 1999 to 2020. Age-adjusted mortality rates (AAMR) per 100,000 population for ITP-related deaths in the United States (US) were extracted by assigning the ICD-10 code D69.3 as the multiple cause of death. AAMRs were stratified according to year, gender, race or ethnicity, and geographical distribution. To observe changes in AAMR, annual percentage change (APC) was calculated via Joinpoint regression using the Joinpoint Regression Program (V 5.1.0, National Cancer Institute).

Results: From 1999 to 2020, a total of 15,660 ITP-related deaths occurred in the US. A decline in the AAMR was observed from 1999 to 2017 (APC: -3.37), before a subsequent increase from 2017 to 2020 (APC: 2.24). A higher overall AAMR was observed in males (0.23) as compared to females (0.18). The AAMR for males declined from 1999 to 2017 (APC: -3.03), but an upward trend was observed from 2017 to 2020 (APC: 2.72). For females, the AAMR decreased from 1999 to 2014 (APC: -4.35), after which the rate of decline decreased for the time period from 2014 to 2020 (APC: -0.41). Thus, an increase in the AAMR was not observed in females in contrast to that observed in males. The highest overall AAMR was observed in non-Hispanic (NH) Whites (0.21) followed by NH African Americans (AA) (0.18). The AAMR for both declined throughout the study period (APC NH Whites: -2.83; NH AA: -4.57). On the other hand, the overall AAMR for Hispanic or Latinos was observed to be 0.17, which decreased from 1999 to 2015 (APC: -5.58). However, a steep increment was noted from 2015 to 2020 (APC: 7.27). Upon stratification by geographical location, non-metropolitan areas were found to have a higher overall AAMR (0.24) in comparison to metropolitan areas (0.19). Furthermore, the AAMR for non-metropolitan areas decreased steadily throughout the study period (APC: -2.60), whereas that for metropolitan areas declined from 1999 to 2013 (APC: -3.92) before the rate of decline decreased for the time period from 2013 to 2020 (APC: -0.66). Among census regions, the Midwest exhibited the highest overall AAMR (0.23), followed by the West (0.22), the South (0.20), and the Northeast (0.20). The trends of AAMR for the Midwest showed variation, as the AAMR increased from 1999 to 2010 (APC: -1.49), with a steeper decrease observed from 2010 to 2013 (APC: -12.3). However, an increment in the AAMR for the Midwest region was observed from 2013 to 2020 (APC: 3.45). The AAMRs for the West, the South, and the Northeast regions decreased steadily from 1999 to 2020 (APC West: -3.09; South: -3.28; Northeast: -3.14). States with the highest overall AAMR were Vermont (0.37), Rhode Island (0.35), and North Dakota (0.32), while Nevada (0.13), the District of Columbia (0.14), and Louisiana (0.15) were among the lowest overall AAMR states.

Conclusion: We observed a decline in ITP-related mortality from 1999 to 2017, with a subsequent increase from 2017 to 2020. The AAMR remained higher in males, NH Whites, non-metropolitan areas, and the Midwest region. Future research should focus on identifying and address the underlying causes of up trending AAMR in ITP patients.