What test should be performed for a patient presenting with a bruise below the eye?

In the context of a patient presenting with a bruise below the eye, performing a Complete Blood Count (CBC) is particularly pertinent. A CBC evaluates various components of blood, including red blood cells, white blood cells, and platelets. The presence of a bruise may raise concerns about potential underlying bleeding disorders or issues with platelet count and function, which are critical in the body's ability to clot.

By analyzing the CBC, healthcare providers can assess whether the platelet count is within normal ranges, as a low platelet count (thrombocytopenia) could lead to increased bruising. Additionally, abnormalities in other blood components could provide insight into systemic issues that might contribute to bleeding.

While the other tests—bleeding tests, Prothrombin Time (PT), and Partial Thromboplastin Time (PTT)—are useful in evaluating coagulation pathways and bleeding tendencies, they do not provide a comprehensive overview of the blood components like a CBC does. Thus, the CBC serves as a foundational screening tool to identify any hematological abnormalities that could explain the bruising.