Background and objective: Idiopathic thrombocytopenic purpura (ITP) is frequently found in general practice. Most patients respond to standard treatment. However, there are about 20-30% of patients become chronic ITP, which responds poorly to treatment. This study aims to study the epidemiology and clinical factors to predict clinical course in adult patients with ITP.

Method: This is a cross- sectional, retrospective study in patients aged 15 years or older who have been diagnosed as ITP at Srinagarind hospital between 1^st January 2002 to 31^st December 2010.

Results: Of 94 patients, 70 patients were female (74%). Mean age was 39 years. Mean follow up duration was 56 months. Fifty five patients were in complete remission, thirty one patients with chronic ITP and three patients died. The analysis of the multiple logistic regression, none of clinical factors were correlated statistically significantly with the clinical course. However, the complete response after first-line treatment, the response after first-line treatment and female sex may be the factors for predicting clinical complete remission with the adjusted Odds ratio (95% CI) of 5.13 (0.8-30.1), 3.54 (0.5 - 22.2) and 2.1 (0.6 - 6.7) respectively, compare with chronic ITP.

Conclusion:  The deep response after first-line treatment and female sex may potentially be the prognostic factors predicting clinical course of complete remission in the long-term follow up in adult patients with idiopathic thrombocytopenic purpura.

Keywords: idiopathic thrombocytopenic purpura, adult, clinical prognostic factors