The determination of the quantity of eosinophils within a cubic millimeter of blood, reflecting the actual number present rather than a percentage, is a valuable diagnostic tool. This method involves multiplying the percentage of eosinophils observed in a differential white blood cell count by the total white blood cell count. For instance, if a patient has a total white blood cell count of 8,000 cells/L and eosinophils constitute 5% of the differential count, the resulting value is 400 eosinophils/L.
This specific measurement holds significant clinical importance in identifying and monitoring various medical conditions. Elevated values can indicate allergic reactions, parasitic infections, certain autoimmune diseases, and even some forms of cancer. Tracking changes in this value over time can be crucial in assessing the effectiveness of treatments and monitoring disease progression. Historically, manual microscopic examination of blood smears was the standard method; however, automated hematology analyzers have largely replaced this, offering improved speed and precision.