Initial labs for all pts should be a CBC w/ diff, reticulocyte count, and peripheral blood smear. These 3 tests will help classify the anemia in microcytic, normocytic, and macrocytic anemia, evaluate bone marrow response, and evaluate RBC morphology.
After you have interpreted the first three tests, order additional tests from the list below to further workup the anemia.
- CBC w/ diff (Look at the Hgb and Hct, MCV, and Platelet count). The hemoglobin is how we define anemia and assess severity; MCV is used to classify the type of anemia as microcytic, normocytic, or macrocytic.
- Reticulocyte count. The reticulocyte count helps us evaluate how the bone marrow is responding to the anemia. This allows us to differentiate b/w hypo-proliferative anemias (e.g. iron deficiency, folate or B12 deficiency) and hyper-proliferative anemias such as hemolysis or acute blood loss.
- Peripheral blood smear: The “blood smear is important in order to determine if there is a small population of red cells with distinctive size or shape abnormalities which would place the patient in either the early microcytic or macrocytic anemia, or would raise suspicion of an acute or chronic hemolytic state (eg, spherocytes, sickle forms, ovalocytes)”
- Stool guaiac or FOBT / Hemoccult.
- Iron studies (Serum iron, serum ferritin, and TIBC) if the anemia has microcytic anemia or normocytic anemia with increased RDW.
- Vitamin B-12 and folate if the patient has macrocytic anemia or normocytic anemia with increased RDW. Methylmalonic acid and homocysteine as needed.
- TSH and fT4 if thyroid disease suspected.
- LDH, haptoglobin, and total and indirect bilirubin if hemolysis is suspected.
- Hemoglobin electrophoresis if thalassemia or hemoglobinopathies suspected. It evaluates the Hemoglobin amino acid chains.
- Serum creatinine if kidney disease is suspected. “The kidneys have a dual role in the pathophysiology of anemia. First, the kidneys produce 90% of the erythropoietin needed to stimulate bone marrow transformation of pluripotent stem cells to proerythroblasts. Any renal dysfunction that interferes with erythropoietin production and release will result in anemia. Second, the hypervolemia associated with acute anemia results in ADH secretion. In response, the kidney will reabsorb water. In direct response to the decreased renal perfusion resulting from acute onset anemia, the kidney will activate the renin-angiotensin system with increased vascular tone and stimulation of aldosterone and resultant increased intravascular volume.” Freeman.
- Liver function tests: The liver function tests contain an LDH, bilirubin, transaminase levels, gamma-glutamyl transferase (GGT) and 5 prime nucleosides
- Abdominal sonogram if an evaluation of spleen size is indicated.
- Bone marrow analysis: A Hematology consult is required to obtain bone marrow biopsy if the anemia is associated with pancytopenia or there are abnormal cells in the peripheral circulation.
- ESR and CRP if you suspect inflammation.
The FOBT at DRMC is called Occult Blood, Fecal Hgb Immunoassay. Also known as Hemoccult. NB: If you enter “Guaiac” test, nothing comes up.
Pearls
- When you diagnose iron deficiency, a search for the cause of the deficiency is mandatory.
- If you suspect hemolysis either from H&P or blood smear, it is confirmed by the finding of increased levels of indirect bilirubin and lactate dehydrogenase, and low levels of haptoglobin
- If you suspect inflammation, consider erythrocyte sedimentation rate or C-reactive protein.
Source:
Andrew M. Freeman; Donald W. Morando. Anemia Screening. https://www.ncbi.nlm.nih.gov/books/NBK499905/
Am Fam Physician 2016;93(4):270-278.
http://www.uptodate.com/contents/approach-to-the-adult-patient-with-anemia
http://www.uptodate.com/contents/causes-and-diagnosis-of-iron-deficiency-anemia-in-the-adult