Long-term clinical outcomes of patients with primary chronic immune thrombocytopenia: a Danish population-based cohort study

Few data exist on the long-term prognosis of patients with chronic primary chronic immune thrombocytopenia (ITP). We examined the risk of infections, hemorrhage resulting in hospitalization, hematologic malignancies, and total and cause-specific mortality among patients with ITP compared with the general population. We used population-based medical databases to identify 407 patients with primary chronic ITP diagnosed during 1996 to 2007 and 4069 general population members individually matched on age, sex, and comorbidity level. We used Cox regression analysis to estimate rate ratios (RRs) adjusted for age (≤ 60 or > 60 years), sex, calendar year, and level of comorbidity. The adjusted 1-year RR of infection was 4.5 (95% confidence interval [CI], 3.3-6.1) for patients with chronic ITP compared with the general population cohort. The adjusted RR decreased to 1.8 (95% CI, 1.3-2.5) for the second to fifth year of follow-up. The adjusted 5-year RR was 3.2 (95% CI, 1.2-9.0) for hospitalized intracranial hemorrhage, 4.4 (95% CI, 2.3-8.3) for other hospitalized hemorrhages, and 4.7 (95% CI, 1.7-12.7) for hematologic malignancy. The 5-year all-cause mortality RR was 2.3 (95% CI, 1.8-3.0). In summary, primary chronic ITP was associated with substantially increased long-term risk of infections, hemorrhagic episodes requiring hospitalization, hematologic malignancies, and mortality.