What does a differential (diff) test analyze in a blood sample?

A differential test, commonly referred to as a "diff," is an important component of a complete blood count (CBC). It specifically analyzes the number and types of white blood cells (WBCs) present in a blood sample. This test is crucial for diagnosing and monitoring various conditions, such as infections, inflammation, and hematological disorders, as different types of white blood cells respond to specific pathogens and other physiological challenges.

By enumerating and categorizing the WBCs, the differential test provides insights into the immune response of the patient. For example, an increase in neutrophils may indicate a bacterial infection, while elevated lymphocyte levels could suggest a viral infection. The detailed breakdown of the cellular composition allows healthcare providers to make informed decisions regarding further diagnostic testing or treatment plans based on the underlying immunological state of the patient.

The other options refer to different aspects of blood analysis. Viscosity relates to the thickness and flow of the blood, which is assessed in separate tests; clotting time measures how long it takes for blood to coagulate, indicating the functionality of the clotting system; while oxygen levels in the blood are typically measured using arterial blood gas tests or pulse oximetry, rather than a differential test. Thus, the differentiation