Isolated monocytosis

Laboratory tests

• FBC
• Blood film
• CRP

Laboratory tests in 3 months

• FBC (repeat for monocytosis)

Laboratory tests

• Blood monocyte phenotyping (in case of persistent monocytosis that is difficult to diagnose)if neededA French review states that flow cytometry phenotyping is not recommended by the WHO and probably remains useful in difficult cases ^[3]. An American review states that it may be considered if the monocytosis persists, and advises bone marrow aspirate straight away when there is an associated rheumatological disease ^[1].
• Antinuclear antibodies (ANA)if needednon-French guidelineSigns suggesting a systemic disease: in persistent monocytosis, autoantibodies and imaging are requested if the clinical picture justifies them ^[1].

Depending on exposure (no routine testing)

• Syphilis serologyif needednon-French guidelineAt-risk sexual exposure or suggestive signs. The search for chronic infection is guided by the exposure history ^[1].
• Brucellosis serodiagnosisif needednon-French guidelineZoonotic risk (livestock farming, abattoir, raw dairy products, stay in an endemic area) with prolonged fever or sweats ^[1].
• Thin and thick blood filmif needednon-French guidelineFever on return from a malaria-endemic area ^[1] (see also the page “Fever on return from travel”).
• IGRA test (QuantiFERON)if needednon-French guidelineRisk of tuberculosis (origin, exposure, immunosuppression) ^[1]. Outside a contact investigation or HIV, the test is not reimbursed in primary care in France.