Absolute monocyte count (AMC) Test

Given that the monocytes are the second line of defence against infections in the body, their count in the blood changes during viral and chronic infections and in the presence of malignancies originating in solid tissues or blood. They also play an important role in cytokine production during inflammation, thereby resulting in increased monocyte count. Normally, WBCs are counted by a differential count. But the results of the differential count are equal to 100%; therefore, a marked increase in any one type of WBC results in the decrease of the other. Hence, the absolute values of WBCs are important. The health implications that suggest the need for AMC test and regular monitoring are as follows:

• Bacterial infections such as tuberculosis, endocarditis and syphilis
• Parasitic, mycotic and rickettsial diseases
• Carcinoma of stomach, breast and ovary; leukaemia and lymphoma
• Ulcerative colitis and enteritis
• Lipid storage diseases
• Surgical trauma
• Collagen diseases and sarcoidosis
• Haemolytic anaemia
• Sepsis
• Lupus erythematosus
• Human immunodeficiency virus (HIV) infection
• Treatment with steroids such as prednisolone

Your healthcare provider will explain the purpose of the test to you before the procedure. It is a simple blood test which does not require fasting; however, meals rich in fats can interfere with the results. Inform your doctor if you are taking any medications as certain drugs such as immunosuppressants and glucocorticoids can lower the monocyte count.

A doctor or lab technician will collect 7 mL of blood from your arm through venepuncture. He/she will label the sample and send it to the laboratory for analysis.

There may be slight inflammation or bruising at the site of injection after the test, though if the symptoms persist, talk to your doctor immediately.

Normal results:

Normal values of AMC range between 100-500 /mm3 or 0.1-0.5 × 109 /L. The exact values might vary slightly according to different laboratories.

Abnormal results:

AMC has a direct associated with conditions such as infection, inflammation and cancer. Hence, abnormal results indicate the increase or decrease in AMC. Monocytosis is the term used for increased monocyte count; whereas, decreased monocyte count is termed as monocytopenia. The abnormal values are as follows: 

• In monocytosis, the monocyte count is more than 500 /mm3 or more than 0.5 × 109 /L
• In monocytopenia, the count is less than 100 /mm3 or less than 0.1 × 109 /L

Monocytosis may suggest the presence of the following health conditions in a patient:

• Neutropenia and bone marrow recovery
• Chronic infections such as tuberculosis, viral infections, congenital syphilis, endocarditis and malaria
• Immune and inflammatory disorders such as collagen vascular diseases, ulcerative colitis, inflammatory bowel syndrome, sarcoidosis and immune thrombocytopenia
• Myocardial infarction
• Gaucher’s disease (lipid storage disease)
• Lymphomas and Hodgkin’s disease
• Myeloid malignancies such as myeloproliferative neoplasm and myelodysplastic syndrome
• Carcinomas
• Lymphoid and plasma cell malignancies
• Sickle cell disease and haemolytic anaemia, lupus erythematosus and severe sepsis indicated by the presence of a small number of phagocytic monocytes in the blood
• Chronic stress

Patients who have undergone splenectomy also have higher monocyte count.

Monocytopenia may indicate the presence of the following conditions in a patient:

• Hairy cell leukaemia
• Overwhelming infection that also causes neutropenia
• HIV infection
• Aplastic anaemia (bone marrow injury)
• Acute stress

Certain medications such as immunosuppressants and corticosteroids may also result in monocytopenia.

In case of abnormal values, it is necessary to further verify the results by supportive examinations, which include the study of monocyte morphology in blood smear and examination of the affected organs and chromosome testing in case of cancer. These tests will help to determine the underlying cause of the abnormal levels of monocytes and decide the line of treatment.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational perspective and is in no way a substitute for medical advice from a qualified doctor.