30th April 2024

A 55-year-old woman presents with a 6-month history of diffuse bone pain and muscle weakness.

A 55-year-old woman presents with a 6-month history of diffuse bone pain and muscle weakness. She mentions feeling more tired than usual and has difficulty climbing stairs. She has a history of coeliac disease and follows a gluten-free diet. On examination, there is tenderness over her long bones and pelvis.

Investigations:

Haemoglobin: 125 g/L (120–160)

White cell count: 6.8 × 10⁹/L (4.0–11.0)

Serum calcium: 2.1 mmol/L (2.2–2.6)

Serum phosphate: 0.7 mmol/L (0.8–1.5)

Serum alkaline phosphatase: 250 U/L (30–130)

Which is the most appropriate next investigation?