From the Guidelines
High monocyte levels, also known as monocytosis, should be evaluated by a healthcare provider to determine the underlying cause, as this condition can indicate an infection, inflammation, or other health issue. Monocytosis is typically defined as a monocyte count greater than 800 cells per microliter [ 1 ]. The most common causes of monocytosis include:
- Bacterial infections, such as tuberculosis or endocarditis
- Viral infections
- Inflammatory conditions, such as inflammatory bowel disease
- Certain cancers, particularly leukemia and lymphoma
- Autoimmune disorders
According to the study published in Haematologica in 2013 [ 1 ], the diagnostic criteria for chronic myelomonocytic leukemia (CMML) include a monocyte count greater than 1 x 10^9/L, bone marrow blasts less than 20%, and associated dysplasia in one or more cell lines.
Treatment for monocytosis targets the underlying cause, rather than the elevated monocyte count itself. For example, antibiotics may be prescribed for bacterial infections, anti-inflammatory medications for inflammatory conditions, or specific treatments for cancer if present [ 2 ].
In terms of evaluation, a complete blood count (CBC) with differential, blood cultures, and possibly a bone marrow examination may be ordered to determine the underlying cause of monocytosis [ 3 ].
It's essential to note that an elevated white blood cell (WBC) count or left shift can indicate a bacterial infection, even in the absence of fever [ 4 ].
Overall, identifying and addressing the root cause of monocytosis is crucial to resolving the condition, and a healthcare provider should be consulted for proper evaluation and treatment.
From the Research
High Monocyte Count
- A high monocyte count, also known as monocytosis, can be caused by a wide variety of neoplastic and non-neoplastic conditions 5, 6.
- The adequate evaluation of monocytosis involves the integration of laboratory data, morphology, clinical findings, and the judicious use of ancillary studies 6.
- Monocytosis is a frequently encountered clinical condition that needs appropriate investigation due to a broad range of differential diagnoses 5.
Diagnostic Approach
- A stepwise diagnostic approach for a patient presenting with monocytosis is recommended, including basic studies and flow cytometry to distinguish between different etiologies 5.
- The complete blood count (CBC) with differential can be used for early sepsis detection, especially in patients without obvious signs of sepsis 7.
- Neutrophil-to-lymphocyte, lymphocyte-to-monocyte, and platelet-to-lymphocyte ratios can be useful for the differential diagnosis of neonatal infection 8.
Risk of Haematological Malignancies
- Monocytosis is associated with an increased risk of all types of haematological malignancy, with the greatest relative risk increase observed in chronic myelomonocytic leukaemia (CMML) 9.
- Sustained monocytosis further increases CMML risk, although the diagnosis is still very rare 9.
- Outside the haematological setting, the absolute risk of haematological malignancy associated with monocytosis is low, and haematological malignancy should mainly be suspected when monocytosis is sustained or the clinical presentation raises suspicion of malignancy 9.