Which initial investigations are recommended for a patient suspected of having leukaemia?

For a patient suspected of having leukaemia, the initial recommended investigation is a very urgent full blood count (FBC) to be performed within 48 hours. This is indicated in adults presenting with symptoms such as pallor, persistent fatigue, unexplained fever, unexplained persistent or recurrent infection, generalized lymphadenopathy, unexplained bruising, unexplained bleeding, unexplained petechiae, or hepatosplenomegaly. In children and young people, a very urgent FBC is also recommended within 48 hours if they present with pallor, persistent fatigue, unexplained fever, unexplained persistent infection, generalized lymphadenopathy, persistent or unexplained bone pain, unexplained bruising, or unexplained bleeding. Additionally, children and young people with unexplained petechiae or hepatosplenomegaly should be referred for immediate specialist assessment. These investigations help to assess for leukaemia and guide further referral and management decisions.