AKT-0226

AKT-0226

A previously healthy 70-year-old woman attends with her daughter, who noted that her mother has had a poor appetite, lost at least 4.5 kg and has lacked energy three months. The patient has not had cough or fever, but she tires easily.

On examination she is rather subdued, is apyrexial and has a pulse of 100 per minute irregular and blood pressure is 156/88 mmHg. Examination of the fundi reveals grade II hypertensive changes. Her JVP is elevated by 8 cm but the neck is otherwise normal.

Examination of the heart and lungs reveals crackles at both lung bases. The abdomen is normal. She has generalised weakness that is most marked in the hip flexors but otherwise neurologic examination is normal.

Investigations reveal:
Haemoglobin 110 g/L (115-165)
White cell count 7.3 ×109/L (4-11)
Urea 8.8 mmol/L (2.5-7.5)

Which of the following would be most useful in establishing the diagnosis?