The Unintentional Detection of Leukemias with Complete Blood Count

The complete blood count (CBC) is the most requested medical test in the world and it is used for various clinical purposes. Due to its characteristic of quantifying red blood cells, white blood cells, and platelets, it assesses bone marrow function, where most leukemias originate. Therefore, the test has the potential to unintentionally detect different types of leukemia. Screening refers to the application of a diagnostic test to a population without signs or symptoms of the disease. Although the request of a CBC in clinical practice does not necessarily constitute screening, the premise that early detection allows more effective treatment, preventing deaths and allowing patients to live longer, may also apply to leukemias. In this article, leukemias and the CBC are used as a didactic platform to explain some aspects regarding potential benefits, harms, and limitations of incidental detection of diseases in asymptomatic individuals and its implications for the primary care clinician.