A nurse is reviewing the laboratory results of a patient diagnosed with thrombocytopenia. Which of the following findings should cause the nurse the most concern?

A. PTT of 32 seconds: This is a normal partial thromboplastin time (typically 25–35 seconds), indicating the intrinsic clotting pathway is functional. B. White blood cell count of 7,000/mm³: This is within the normal range (5,000–10,000/mm³). C. Hemoglobin level of 13.5 g/dL: This is a normal hemoglobin level for an adult. D. Platelet count of 15,000/mcL: Normal platelet counts are 150,000–400,000/mcL. A count below 20,000/mcL is a critical value that places the patient at high risk for spontaneous, life-threatening bleeding (e.g., intracranial hemorrhage).