You are seeing a fifty-year-old female in GP who has presented with loin pain. On questioning this patient reports that she has had pain for the last few weeks. This patient reports no pain when passing urine but does report increased waking in the night to urinate recently. On examination you note palpable kidneys and splenomegaly. You do some observations and you notice the patient’s blood pressure is slightly elevated at 135/87. You suspect polycystic kidney disease so you conduct a full blood count. Which of the following components of blood is most likely to be elevated in this condition?