The volume of blood typically drawn for a Complete Blood Count (CBC) or White Blood Count (WBC) is small, and not likely to result in anemia on its own. Even in the case of neutrophil counts for clozapine, which are drawn weekly early in the course of treatment, this is still the case. The REMS for clozapine requires absolute neutrophil counts (ANCs), and no other components of the CBC. However, many people request a CBC because a WBC count does not always include a differential or ANC, and a CBC provides an opportunity to see problems with other cell lines and to detect unrelated infections. The blood volume drawn can be independent of which test is ordered. Guidelines recommend a CBC as part of the baseline assessment of people with serious mental illness. Guidelines also recommended regular metabolic screening tests for many people with serious mental illness, but these do not include a CBC. Lab reference ranges differ. For many lab tests, a lab’s reference range includes values that are analyzed and reported for the middle 95% of the reference population. With a “two-tailed” reference range, 2.5% of normal adults will have values outside the reference range. Lab errors also occur. These can be apparent with repeat testing, as can trends in blood counts.
With regard to potential causes of anemia, these are numerous. One option is a referral to primary care. Anemia can be understood as having three categories of causes: blood loss, hemolysis, or decreased production. Causes of blood loss include menstrual bleeding, colon cancer, other cancers, pain relievers, ulcers, and gastritis. Causes of hemolysis include sickle cell anemia, other hemolytic anemias, thalassemia and malaria. Causes of decreased production include iron deficiency (can include low mean corpuscular volume), vitamin deficiencies (B12, folate, other substances), anemia of chronic disease (chronic inflammatory diseases including cancer, HIV, rheumatoid arthritis, Crohn’s disease), kidney diseases, bone marrow diseases, chemotherapy and other medications. Initial evaluation of chronic anemia depends on an individual’s risk, speed of onset, and trends, such as trending down over time. Depending on these factors, tests can include colon cancer screening; serum iron, ferritin and TIBC; B12 and folate levels; bilirubin or LFTs; thyroid panel; kidney function (GFR); or inflammatory markers (ESR or CRP).