30th April 2024

A 25-year-old woman presents with a 3-month history of unexplained weight loss, chronic diarrhoea, and persistent generalised itching.

A 25-year-old woman presents with a 3-month history of unexplained weight loss, chronic diarrhoea, and persistent generalised itching. She reports a rash over her trunk and arms. She has a history of multiple sexual partners and occasional intravenous drug use. She denies any previous blood transfusions or travel outside the country.

Investigations:

Temperature: 38.2°C

Physical examination: Diffuse maculopapular rash, oral thrush, and generalised lymphadenopathy 

FBC: Mild anaemia, lymphopenia

Which is the most appropriate diagnostic investigation?