What is the initial step in a basic anemia workup?

From the Guidelines

The initial step in a basic anemia workup is obtaining a complete blood count (CBC) with differential, as it provides essential information about hemoglobin levels, red blood cell count, mean corpuscular volume (MCV), and other parameters that help characterize the type of anemia present. This test is crucial in classifying anemia as microcytic, normocytic, or macrocytic, which narrows down potential causes 1. The CBC results can indicate microcytic anemia (< 80 fL), which is most commonly caused by iron deficiency, normocytic anemia (80–100 fL), which may be caused by hemorrhage, hemolysis, or bone marrow failure, or macrocytic anemia (> 100 fL), which is most often megaloblastic, indicating vitamin B12 or folate deficiency 1.

Some key points to consider in the initial workup include:

• The morphologic approach to evaluating anemia, which characterizes anemia based on the MCV, reported in the initial CBC test 1
• The kinetic approach, which focuses on the underlying mechanism of anemia, distinguishing among the production, destruction, and loss of RBCs, with the reticulocyte count being a key indicator of RBC production capacity 1
• The importance of considering the reticulocyte count, as a low or 'normal' reticulocyte count may indicate an inability to respond properly to anemia, while an increased reticulocyte count may indicate increased red cell formation 1

After obtaining the CBC results, further targeted testing can be pursued based on the initial findings, such as:

• Iron studies for suspected iron deficiency, including serum ferritin and transferrin saturation levels 1
• Hemolysis workup for suspected hemolytic anemia, including tests for haptoglobin, lactate dehydrogenase, and bilirubin levels 1
• Vitamin B12 and folate levels for macrocytic anemia 1

This stepwise approach ensures efficient diagnosis while avoiding unnecessary testing, and is supported by the most recent and highest quality studies, including those published in the Journal of the National Comprehensive Cancer Network and the Journal of Crohn's and Colitis 1.

From the Research

Initial Steps in a Basic Anemia Workup

The initial step in a basic anemia workup involves a thorough history and physical examination, along with a complete blood cell count (CBC) [ 2 ].

Laboratory Evaluation

• A complete blood count and reticulocyte count are the first steps in the laboratory evaluation of anemia [ 3 ].
• The anemia is then categorized as microcytic, macrocytic, or normocytic, with or without reticulocytosis [ 3 ].
• Examination of the peripheral smear and a small number of specific tests confirm the diagnosis [ 3 ].

Diagnostic Tests

• Serum ferritin is the preferred initial diagnostic test for iron deficiency anemia [ 4 ].
• Total iron-binding capacity, transferrin saturation, serum iron, and serum transferrin receptor levels may be helpful if the ferritin level is between 46 and 99 ng per mL [ 4 ].
• An iron panel (ie, ferritin and iron levels, total iron-binding capacity, transferrin saturation) and levels of vitamin B12, folate, lactate dehydrogenase, haptoglobin, and bilirubin may be included in the supplemental tests [ 2 ].

Classification and Cause of Anemia

• Careful examination of the CBC and the mean corpuscular volume provides important clues to the classification and cause of anemia [ 2 ].
• The differential diagnosis of anemia of chronic diseases is primarily based on the exclusion of other types of anemia, in particular iron deficiency [ 5 ].