“…To specifically select patients with unprovoked VTE at the time of initial enrollment, we excluded patients diagnosed with malignant cancer (ICD‐9 codes 140–208, concomitantly registered with catastrophic illness), autoimmune diseases (ICD‐9 codes 696.0, 696.1, 696.8, 710.0, 710.1, 710.2, 710.3, 710.4, and 714.0), or iatrogenic pulmonary embolism and infarction (ICD‐9 codes 415.11). Notably, because the issue of catastrophic illness is associated with the payment of the NHI, the coding of cancer and autoimmune diseases are validated to achieve a high accuracy . We also excluded patients who were pregnant at the time of enrollment (ICD‐9 codes 671.3, 671.4, 673, and 673.2) or were immobilized anytime during the 3 months before diagnosis owing to major surgeries or systemic diseases (ICD‐9 codes 820–823, procedure code 81.51, 81.52, 81.53, and 81.54).…”