PB0679 - Natural History of Untreated Adult Immune Thrombocytopenia (ITP)

Background: International guidelines recommend that Immune thrombocytopenia (ITP) patients who have platelet > 30x10^9/L require no treatment. However, data on clinical courses and risk factors are lacking.

Aims: To study the natural history of untreated ITP

Methods: The cohort study included adult primary ITP patients (platelet count 30-150x10^9/L) who were followed up at Chulalongkorn Hospital from January 2015 to October 2022. Treatments were given for platelet count < 30x10^9/L and/or major bleeding. The proportional hazard regression model was used for the risk factors.

Results: There were 73 untreated ITP patients. The mean age was 62 (SD 16.64), years old, and 56% of them were female. The median follow-up time was 3 years comprising 272.48 patient-years. The proportion of ITP patients who subsequently required treatment was 23.3% (17/73) with the incidence rate of 6.24%/year (95%Confidence interval [CI] 3.88-10.0%) as shown in Figure 1. The risk factors that could predict this event were: age < 35 years old (Hazard ratio [HR] 4.03; 95%CI 1.3-12.52, P-value 0.016) and maximum-minimum platelet counts during follow-up (excluding the count that required treatment) ≥ 70x10^9/L (HR 2.94; 95%CI 1.03-8.37, P-value 0.044). The baseline platelet < 100x10^9/L showed a trend towards the poor outcome (HR 2.9; 95%CI 0.95-8.9, P value 0.063). The spontaneous recovery rate was 10% (7/73) with the incidence of 2.57%/year (95%CI 1.22-5.93%). No significant risk factor for spontaneous recovery was observed. The characteristics of each group are shown in Table 1. Patients who had platelet counts > 100 x 10^9/L persisting for over 3 and 6 months showed better prognosis. There was no patient who showed secondary causes of ITP during follow-up.

Conclusion(s): The majority of untreated ITP patients showed good prognosis. Risk factors for subsequent treatments were younger age and wide variations in platelet counts.