What are the key clinical features that may indicate an underlying serious condition in a patient with low platelet counts?

Key clinical features indicating an underlying serious condition in a patient with low platelet counts include:

• Platelet count less than 20 × 10⁹/L or presence of active bleeding, which requires immediate referral or urgent specialist advice due to high risk of spontaneous haemorrhage.
• Platelet count less than 50 × 10⁹/L, warranting urgent referral.
• Platelet count between 50–100 × 10⁹/L accompanied by evidence of pancytopenia (haemoglobin <100 g/L, neutrophils <1 × 10⁹/L), splenomegaly, lymphadenopathy, pregnancy, or upcoming surgical/interventional procedures, indicating need for urgent referral.
• Persistent and unexplained thrombocytopenia (platelet count <100 × 10⁹/L) on at least two occasions 4–6 weeks apart, suggesting referral to haematology.
• Unexplained bruising, petechiae, or bleeding symptoms, especially if full blood count results suggest leukaemia or other haematological malignancies.
• Signs of hepatosplenomegaly or lymphadenopathy, which may indicate malignancy or bone marrow pathology.
• In children and young people, unexplained petechiae, hepatosplenomegaly, or full blood count suggestive of leukaemia require immediate specialist assessment.
• In adults, full blood count results suggestive of leukaemia or unexplained bleeding/bruising require urgent haematology referral.

These features should prompt urgent investigation and referral to exclude serious underlying causes such as haematological cancers, severe bone marrow failure, or other critical conditions.

References: ¹,²,⁵