Myelofibrosis (NORD)

A 65-year-old female comes to her primary care physician’s office for evaluation of fatigue, weakness, and 8 kg (17.6 lb) unintentional weight loss over the past two-months. In addition, the patient reports having a decreased appetite. Her medical history is notable for a viral upper respiratory tract infection that self-resolved six weeks ago. Physical exam reveals oral mucosal pallor. Cardiac and pulmonary exams are non-contributory. Abdominal exam reveals an enlarged liver and spleen. A fecal occult blood test is negative. Complete blood count reveals a leukocyte count of 3,700/mm3 and platelet count of 98,000/mm3. A peripheral blood smear is ordered and the results are as follows:  



Reproduced from: Wikimedia Commons

Which of the following findings would help confirm this patient’s diagnosis?