From the Guidelines
Elevated monocytes, or monocytosis, is a condition that requires prompt evaluation by a healthcare provider to determine the underlying cause, as it can be associated with various inflammatory, infectious, or malignant conditions, and treatment should target the underlying cause rather than the monocyte count itself. The presence of elevated monocytes can indicate an ongoing inflammatory or immune response in the body, and common causes include chronic infections, inflammatory conditions, certain cancers, and recovery from acute infections 1. According to the 2017 Infectious Diseases Society of America clinical practice guidelines, a monocyte predominance may suggest the presence of an intracellular pathogen such as Salmonella 1.
Key Considerations
- Elevated monocytes can be associated with various conditions, including chronic infections, inflammatory conditions, and certain cancers
- Treatment should target the underlying cause rather than the monocyte count itself
- Additional tests, such as a complete blood count with differential, inflammatory markers, and possibly imaging studies or biopsies, may be recommended to determine the underlying cause
- Monocytes play a crucial role in the immune system by engulfing pathogens, presenting antigens to other immune cells, and producing inflammatory cytokines
Diagnostic Approach
- A complete blood count with differential can help identify the presence of elevated monocytes
- Inflammatory markers, such as C-reactive protein or erythrocyte sedimentation rate, can help determine the level of inflammation
- Imaging studies, such as chest X-ray or computed tomography, may be recommended to evaluate for underlying conditions, such as pneumonia or lymphoma
- Biopsies, such as bone marrow biopsy, may be recommended to evaluate for underlying conditions, such as leukemia or lymphoma
Management
- Treatment should target the underlying cause of the elevated monocytes, rather than the monocyte count itself
- Antibiotics may be recommended for bacterial infections, such as tuberculosis or endocarditis
- Anti-inflammatory medications may be recommended for inflammatory conditions, such as rheumatoid arthritis or inflammatory bowel disease
- Chemotherapy or radiation therapy may be recommended for certain cancers, such as leukemia or lymphoma. A study published in the European Heart Journal in 2004 found that monocyte count is highest in malignant effusions and hypothyroidisms 1.
From the Research
Elevated Monocytes
- Elevated monocytes, also known as monocytosis, can be caused by a wide variety of neoplastic and non-neoplastic conditions 2.
- The evaluation of monocytosis involves the integration of laboratory data, morphology, clinical findings, and the judicious use of ancillary studies 2.
- A stepwise diagnostic approach is recommended for patients presenting with monocytosis, including basic studies and flow cytometry to distinguish between different etiologies 3.
- Monocytosis can be associated with immune suppression, increasing the risk of infective co-morbidity and death, particularly in high-risk surgical patients 4.
- Clinical factors influencing monocyte function include trauma, major elective surgery, and overt sepsis, which can lead to a cascade of immunological change 4.
- Markers of monocyte impairment, such as depressed HLA-DR expression, can be predictive of nosocomial infection, multi-organ failure, and death in some surgical patients 4.
- Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are markers of inflammatory conditions that can be used in conjunction with clinical history and physical exam to diagnose and monitor pathological conditions, including those associated with elevated monocytes 5, 6.