Which laboratory test is most important to obtain before a dental procedure in a patient with hemophilia?

Hemophilia A (factor VIII deficiency) and Hemophilia B (factor IX deficiency) involve defects in the intrinsic coagulation pathway, which is monitored by the activated partial thromboplastin time (aPTT). The PTT will be prolonged in hemophilia because factors VIII and IX are part of the intrinsic pathway. The PT/INR primarily reflects the extrinsic pathway (factor VII and beyond) and would be normal in hemophilia. Before dental procedures in hemophiliac patients, the PTT, factor levels (VIII or IX), and consultation with a hematologist are essential. The bleeding time is less commonly used and reflects platelet function rather than clotting factor deficiencies.