30th April 2024

A 72-year-old female with a history of rheumatoid arthritis complains of increasing tiredness and shortness of breath on exertion.

A 72-year-old female with a history of rheumatoid arthritis complains of increasing tiredness and shortness of breath on exertion. She has been on methotrexate and prednisolone for the past five years.

Investigations:

Haemoglobin: 105 g/L (120–160)

White cell count: 6.2 × 10^9/L (4-11)

Platelets: 190 × 10^9/L (150-450)

MCV: 88 fL (80–96)

Serum iron: Normal

TSH: Normal

Which additional investigation is most likely to help with the diagnosis?