A patient presents to her GP with recurrent nosebleeds and also complains of facial fullness and facial pain. Over the past 2 months she has developed progressive shortness of breath and on one occasion she coughed up some blood. On looking through the patient notes, the GP notices that the patient was recently admitted to hospital with haematuria and proteinuria. What would be the most appropriate test to perform? a. ACE levels b. Quantiferon TB Gold test c. Anti-neutrophil cytoplasmic antibodies d. Factor VIII levels