Anemia means loss of red blood cells (RBCs) (see Complete Blood Count for a discussion of the types of blood cells we have). We measure RBCs by the amount of hemoglobin in the blood. Normal is around 14 grams for men, children, and women after menopause; women with menstrual periods have about 13 gm.
Most people with anemia have no symptoms at all. When hemoglobin falls below 8 or 9 gm, there can be fatigue, or especially shortness of breath during exertion. Below 7 gm a person may begin to look pale, and the feet may swell. A person with blocked coronary arteries (en route to a heart attack), that they never realized they had, may get chest pain. Symptoms may occur at higher levels of hemoglobin if blood loss happens quickly. See our topic Anemia (acute).
The danger of anemia is not necessarily just from symptoms. Suppose a man has a hemoglobin of 12 gm. He won’t feel a thing in the world, and there’s no danger to his body. But suppose the cause of his low-grade blood loss happens to be stomach cancer. That’s bad.
Anemia does not necessarily mean low iron. That’s a common cause, but not the only one. It can also occur because of low levels of vitamin B12 or Folic Acid. There are certain genetic types of anemia (Thalassemia, Sickle Cell, etc.). Some diseases make RBCs break apart (hemolytic anemia, not so common). If we give iron to everyone with anemia, some people will accumulate too much, and ruin their livers.
A common cause of low-grade anemia in older persons is called “Anemia of Chronic Disease” (ACD), which really just means that the body isn’t making enough new RBCs. An RBC lives 4 months; our bone marrow makes new ones all the time. This production can slow down for a lot of reasons, like chronic diseases, but also medications, and certain types of blood cancer. Acute conditions can also temporarily slow down the bone marrow, and we still say “Anemia of Chronic Disease,” even though things will return to normal.
The first step is to diagnose Anemia, which is easy. We order a Complete Blood count (CBC), and find a low hemoglobin. Then we have to determine what kind of anemia, based on the size of the RBCs, which is measured by the lab as a number called “MCV” (values are more-or-less):
- Microcytic (small RBCs) = MCV <80
- Normocytic (normal-sixed RBCs) = MCV 80-100
- Macrocytic (large RBCs) = MCV >100
Once we know the type of anemia, we list out the possible causes, & do appropriate lab tests below. An excellent test is the “peripheral smear,” examining the RBCs under a microscope. We discuss some of the diseases below (& their tests) in more depth (click the links).
- Iron Deficiency >> “Iron Studies”: Ferritin (low), Transferrin Saturation % (low)
- Thalassemia >> “Iron Studies” are normal. RBCs are all microcytic (not just some)
- Lead Poisoning >> “Baophilic stippling” on peripheral smear
- Acute Bleeding >> figure it out from patient’s history. Reticulocyte count (high)
- Hemolysis (RBCs breaking apart) à Bilirubin (high), Haptoglobin (low), LDH (high)
Reticulocyte count (very high, near 10%)
- Anemia of Chronic Disease à All the above tests are normal.
- Vitamin B12 Deficiency >> Vitamin B12 blood level (low).
- Folic Acid Deficiency >> Folic Acid blood level (low)
- Cirrhosis >> Liver Function Tests in blood
- Alcoholism >> Get an honest history from patient
- Myelodysplasia (failure to make new blood cells) >> Complete Blood Count
Just to make this more complicated, some patients may have a “mixed anemia.” Suppose somebody with Iron Deficiency develops Vitamin B12 Deficiency. The first causes small RBCs (low MCV), the second large RBCs (high MCV), so the final result on the lab test may average out to a normal MCV.
That’s why looking under the microscope at a peripheral smear can give an idea if there are lots of different sizes of RBCs. A test that comes with the CBC called “red cell distribution width” (RDW) can help. If the RDW is high, there are lots of different sized RBCs. A normal RDW means the RBCs are pretty much the same size (whatever that is).
The natural course of Anemia, and the treatment, all depend on its cause. And the cause of the cause. For example, a patient feels fatigued. We order a CBC and diagnose Anemia. We order additional tests to diagnose Iron-Deficiency Anemia. Then we order a colonoscopy & find bowel cancer. We don’t just stop with saying, “You have Anemia.” We have to know “Why?”