Anemia is defined as a Hb less than 12 grams per deciliter of blood (g/dL) in non-pregnant women, less than 11 g/dL in pregnant women, or under 13 g/dL in men.[1][2][3]
Iron deficiency is the most common cause of anemia. Serum ferritin testing is recommended in patients with anemia to diagnose iron deficiency, as it has good accuracy compared to the (invasive) gold standard for diagnosis of bone marrow biopsy. It is the best biochemical test to indicate iron stores, and a ferritin level below 30 micrograms per liter of blood (µg/L) can indicate iron deficiency in anemia.
Serum ferritin is also an acute phase reactant — in other words, a marker of inflammation — therefore, C-reactive protein should also be measured to rule out a false elevation of ferritin from an inflammatory condition or infection. Depending on the condition, a cutoff value of less than 100 µg/L may be used for ferritin.[1][4][3]
Iron deficiency anemia may also show the following signs on bloodwork:
- Mean corpuscular volume (MCV), a measure of RBC size: less than 80 femtoliters (fL)
- Mean cell hemoglobin (MCH), a measure of RBC iron content: less than 25 g/dL
- Percentage transferrin saturation less than 16% (or <20% in the presence of inflammation)[5][4][3]
In addition: serum transferrin may be high, serum iron may be low, and total iron-binding capacity may be high.[6][7]
If iron deficiency anemia is diagnosed, and the clinician suspects it may have a gastrointestinal cause, then tests such as a urea breath test (for H. pylori infection), serologic testing for celiac disease (tissue transglutaminase IgA), fecal occult blood testing (i.e., stool sample), upper endoscopy (i.e., viewing the esophagus, stomach, and upper intestines), or colonoscopy may also be performed to investigate for causes of blood loss.[1][6]