Monocytes
Overview
Monocytes measure the absolute number or percentage of circulating monocytes, a type of white blood cell that constitutes 2-8% of total leukocytes and differentiates into macrophages and dendritic cells in tissues. These cells participate in immune surveillance, phagocytosis of pathogens, antigen presentation, and cytokine production during inflammation. Elevated levels (monocytosis) indicate chronic infections, inflammatory disorders, or hematologic malignancies, while low levels (monocytopenia) suggest bone marrow suppression or acute overwhelming infections. Clinically, monocyte counts contribute to the complete blood count differential for infection monitoring and leukemia diagnosis.
Clinical Use Cases
- Evaluating chronic infections (tuberculosis, subacute bacterial endocarditis).
- Monitoring inflammatory conditions (inflammatory bowel disease, sarcoidosis, autoimmune disorders).
- Assessing hematologic malignancies (chronic myelomonocytic leukemia, chronic myeloid leukemia).
- Identifying bone marrow recovery after chemotherapy or aplastic anemia.
Specimen Types
- Whole blood (EDTA anticoagulant preferred).
Measurement Methods
- Automated hematology analyzer flow cytometry.
- Manual differential count on peripheral blood smear.
- Impedance and light scatter analysis.
Test Preparation and Influencing Factors
- No fasting required; standard venipuncture.
- Corticosteroids cause transient monocytosis.
- Recent viral infections or stress transiently decrease counts.
- Splenectomy causes persistent mild monocytosis.
Synonyms
- Absolute monocyte count (AMC).
- Monocyte percentage.