Medical Laboratory Scientist ASCP Practice Exam 2025 – Complete Study Guide

Brilliant cresyl blue is primarily used for detecting reticulocytes, which are immature red blood cells that contain residual RNA. When this stain is applied, it binds to the RNA present in the reticulocytes, allowing them to appear as more intensely colored compared to mature red blood cells that lack this RNA. This differential staining helps laboratory professionals identify and quantify reticulocytes in a blood sample, providing valuable information about bone marrow function and erythropoiesis (the production of red blood cells).

The other options are associated with different staining methods or techniques. For instance, staining leukocytes is typically performed using stains like Wright's stain or Giemsa stain, while identifying bacteria in culture often employs Gram staining or specialized media. Observing platelets generally does not require a specific stain like Brilliant cresyl blue; instead, standard blood smears are used to assess platelet counts and morphology. Thus, the use of Brilliant cresyl blue is specifically tied to reticulocyte detection, highlighting its importance in hematology.