Which of the following would be MOST consistent with a diagnosis of hypofibrinogenemia?
a) Prolonged PTT, Normal INR, Normal platelet count
b) Prolonged PTT, Prolonged INR, Low platelet count
c) Normal PTT, Prolonged INR, Normal platelet count
d) Prolonged PTT, Prolonged INR, Normal platelet count
e) Normal PTT, Normal INR, Normal platelet count
Answer d. Fibrinogen is part of the final common pathway for both PTT and PT/INT assessment. Patients with isolated low fibrinogen levels would be expected to have prolongation of both tests, but no quantitative or qualitative abnormalities of platelets. However, note that a common cause of hypofibinogenemia is disseminated intravascular coagulation (DIC); this disease is also characterized by consumption of platelets, and answer (b) would be consistent with DIC.