A 66 year old man has tiredness and low back pain for 2 months. He has type 2 diabetes and hypertension and takes metformin and ramipril. He is a non-smoker and does not drink alcohol.
His pulse rate is 88 bpm and BP 138/82mmHg. Clinical examination is normal.
Haemoglobin 78 g/L (130–175)
White cell count 3.4 × 109/L (3.0–10.0)
Platelet count 80 × 109/L (150–400)
Corrected calcium 2.71 mmol/L (2.2–2.6)
Albumin 36 g/L (35–50)
X-ray of lumbar spine: generalised osteopenia and vertebral collapse at multiple levels.
Which is the most appropriate next investigation?
- Serum angiotensin converting enzyme
- Serum parathyroid hormone
- Serum prostate specific antigen
- Serum protein electrophoresis
- Serum vitamin D