Background: Paraspinal extramedullary hematopoiesis (EMH) is uncommon, but it is one of major complications of increased morbidity in patients with thalassemia.
Objective: To develop a clinical risk score for predicting paraspinal extramedullary hematopoiesis in patients with thalassemia.
Material and Method: A retrospective study was conducted in adult patients with thalassemia at Srinagarind Hospital, Khon
Kaen University (KKU) and Udonthani Hospital, Thailand. Paraspinal EMH was defined as radiologic evidence of EMH foci
with or without symptoms. The clinical parameters significantly associated with EMH were entered into the logistic regression
model. The risk score was derived from the final model’s coefficients. A receiver-operating characteristic (ROC) curve was
constructed to determine the area under the ROC curve and the cut-off point.
Results: The KKU-EMH score included: 1) age greater than 25 year (2 points) and 2) thalassemic facie (3 points). Using the
cut-off of 5 points, the score showed good discrimination with an area under the ROC curve of 0.83 (95% CI 0.76 to 0.90).
Conclusion: Advanced age and thalassemic facie are independent risk factors for paraspinal EMH in patients with
thalassemia. The KKU-EMH score is a practical score. It can be used as a screening tool for paraspinal EMH in patients with
β-thalassemia.

Keywords: Paraspinal extramedullary hematopoiesis, Risk score, Thalassemia