A 72 year-old female was admitted to the hospital and had undergone elective cardiac surgery for aortic valve replacement. She was administered heparin for the prevention of thrombosis. On the second day of her admission, she developed a urinary tract infection and was started on trimethoprim-sulfamethoxazole. On the sixth day of her hospital stay, she developed fever, chills, hypertension, tachycardia, chest pain and shortness of breath. On physical examination, you noticed pain, redness, and swelling of her right arm. A severe rash developed in the skin where heparin was given. The attending nurse reports that she is meticulously administering heparin via intravenous route and using heparin flushes before using intravenous lines. Ultrasound of the right arm revealed deep venous thrombosis and a CT angiogram revealed a blood clot in the right lung. Laboratory tests reveal the following: Erythrocyte count (RBC) 4.2 million/mm³ Male: 4.3 – 5.9 million/mm³ Female: 3.5 – 5.5 million/mm³ Erythrocyte sedimentation rate (Westergren) 12 mm/h Male: 0-15 mm/h Female:0-20 mm/h Hematocrit 39% Male:41% – 53% Female: 36% – 46% Hemoglobin, blood 13.4 g/dL Male:13.5-17.5 g/dL Female 12.0 – 16.0 g/dL Leukocyte count (WBC) 7200 /mm³ 4500-11,000/mm³ Neutrophils, segmented 56% 54% – 62% Neutrophils, bands 4% 3% – 5% Eosinophils 1% 1% – 3% Basophils 0.5% 0% – 0.75% Lymphocytes 28% 25% – 33% Monocytes 4% 3% – 7% CD4+ T-lymphocyte count 1100 /mm³ ≥500/mm³ Platelet count 40,000/mm³ (on the day of admission: platelet count was 340,000/mm³ 150,000 – 400,000/mm³ Reticulocyte count 1.0% 0.5% – 1.5% D-Dimer 450 ng/mL ≤250 ng/mL Partial thromboplastin time (aPTT) (activated) 27 seconds 25-40 seconds Prothrombin time (PT) 10 seconds 11-15 seconds Mean corpuscular hemoglobin (MCH) 29 pg/cell 25 – 35 pg/cell Mean corpuscular hemoglobin concentration (MCHC) 34% Hb/cell 31% – 36% Hb/cell Mean corpuscular volume (MCV) 94 μ m³ 80-100 μ m³ 4T score 7 PF4 ELISA Test Positive Regarding this complication patient developed in the hospital, which of the following is true about its risk factors?
