Explanation: This child has a pulmonary embolism (PE) originally mistaken for pneumonia. The best test to confirm the diagnosis of PE is specific imaging of the pulmonary vasculature such as CT angiography. Echocardiogram can help see if there is evidence of right heart strain, which can determine aggressiveness of therapy. D-dimer testing is helpful in adults with PE and has a good negative predictive value. However, its utility in children and adolescents has not been demonstrated. If there is an index of suspicion for PE, imaging should be done regardless of the D-dimer result. APCR and protein S activity testing may be abnormal in a girl on OCPs and would explain why thrombus developed, but they would not confirm the diagnosis of PE nor guide therapy.
Question 11
