Prognostic risk-stratified score for predicting mortality in hospitalized patients with thrombotic thrombocytopenic purpura: nationally representative data from 2007 to 2012

Abstract

Background: Despite proven efficacy and increased availability of therapeutic plasma exchange (TPE), mortality for patients with thrombotic thrombocytopenic purpura (TTP) remains high with a limited understanding of those at highest risk of death.

Study design and methods: This study utilized the Nationwide Inpatient Sample (2007-2012) to derive a prognostic score for mortality in hospitalized TTP patients. Odds ratios of death with various putative risk factors adjusted for age, sex, and race were calculated (adjOR). Weighted mean of adjOR estimates were incorporated in a risk-stratified score.

Results: Among 8203 hospitalizations with TTP as primary admission diagnosis who underwent TPE, 613 deaths were identified (all-cause mortality, 7.5%; median time-to-death, 9 days; interquartile range, 4-14 days). In multivariable logistic regression, arterial thrombosis (adjOR 6.7, 95% confidence interval [CI], 1.1-40.9), intracranial hemorrhage (adjOR, 6.1; 95% CI, 1.6-23.2), age at least 60 years (adjOR, 3.5; 95% CI, 2.1-5.6), renal failure (adjOR, 2.6; 95% CI, 1.5-4.5), ischemic stroke (adjOR, 2.4; 95% CI, 1.2-5.0), platelet (PLT) transfusions (adjOR, 2.2; 95% CI, 1.2-4.1), and myocardial infarction (adjOR, 2.3; 95% CI, 1.2-4.6) were significant independent predictors of mortality in TTP patients who underwent TPE. A prognostic weighted mortality prediction scoring system incorporating arterial thrombosis, intracranial hemorrhage, age, renal failure, ischemic stroke, PLT transfusion, and myocardial infarction showed very good discrimination and was predictive of 78.6% deaths.

Conclusions: Early and targeted therapy for high-risk individuals should be used to guide management of TTP patients for improved survival outcomes.

Figure 1

Receiving Operator Character (ROC) Curve with each factor being added to the stepwise logistic regression model. Final area under the ROC curve after all model building steps: 78.6%.

Figure 2

Mortality in TTP score (MITS): Total TTP mortality score and corresponding observed percentage of in-hospital TTP deaths in patients who underwent TPE (Using the Nationwide Inpatient Sample 2007–2012). Total mortality score was calculated based on a weighted average of the odds ratio estimates from the multivariable model for TTP patients who underwent TPE and corresponding reported percentage of deaths. There were too few to report numbers and percentages at TTP score of 7 and results are not shown per HCUP data use guidelines.