Which is the best first test to evaluate RBC disorders?

The best first test to evaluate red blood cell (RBC) disorders is a complete blood count (CBC) with a peripheral smear. This combination allows for a thorough assessment of multiple aspects of the red blood cells, including their number, size, shape, and distribution, as well as providing critical information about other blood components.

The CBC offers essential parameters such as hemoglobin levels, hematocrit, and red blood cell indices (MCV, MCH, and MCHC), which help identify the presence of anemia, polycythemia, or other hemolytic conditions. When coupled with a peripheral smear, it allows for microscopic examination of the blood cells, enabling detection of abnormalities in red blood cell morphology, such as spherocytes, target cells, or any signs of hemolysis and other hematological disorders.

Other options like a comprehensive metabolic panel are focused on assessing metabolic functions and organ health, providing limited information about RBC-specific issues. Blood type and crossmatch are essential for transfusion purposes but do not evaluate RBC disorders directly. The CBC with differential would provide useful white blood cell data, but the absence of the peripheral smear means it would lack the critical visual assessment needed for a comprehensive RBC evaluation. Therefore, the CBC with peripheral