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The bleeding risk and natural history of idiopathic thrombocytopenic purpura in patients with persistent low platelet counts.

BACKGROUND
No firm data are available on the natural history of idiopathic thrombocytopenic purpura (ITP) or on mortality rates or frequency of major bleeding episodes associated with this condition. The disease is thought to have a relatively benign course, despite the frequent occurrence of very low platelet counts. This prevailing conception often guides therapeutic decisions.


OBJECTIVE
To estimate the bleeding risk of ITP involving persistent low platelet counts (<30 x 10(9)/L) and its impact on prognosis.


DESIGN
Age-adjusted bleeding risk was derived from a pooled analysis of ITP clinical series based on a systematic literature search. The risk estimate was incorporated into a Markov model to determine its impact on prognosis.


RESULTS
Seventeen case series complied with inclusion criteria, including 1,817 patients with ITP. There were 49 cases of fatal hemorrhage over an estimated 1,258 to 3,023 patient-years at risk. The rate of fatal hemorrhage before age adjustment was estimated at between 0.0162 and 0.0389 cases per patient-year. Age-adjusted rates were 0.004, 0.012, and 0.130 cases per patient-year for age groups younger than 40, 40 to 60, and older than 60 years, respectively. Predicted 5-year mortality rates ranged from 2.2% for patients younger than 40 years to 47.8% for those older than 60 years. A 30-year-old woman remaining thrombocytopenic due to ITP was predicted to lose 20.4 years (14.9 quality-adjusted life years) of her potential life expectancy. At age 70, predicted loss was 9.4 years (5.0 quality-adjusted life years).


CONCLUSIONS
Idiopathic thrombocytopenic purpura with persistent low platelet counts carries a grave prognosis. Therefore, an active therapeutic approach in the clinical management of affected patients should be considered. In view of the significant potential implications of the model results, we call for initiating a well-designed prospective inception cohort study of patients with ITP.