A 63 year old male presents with a history of pain in his joints
and difficulty in hearing.
There is no past illness of note. He does not smoke or drink
On examination you note that he has sensorineural deafness in his
left year. You also note osteoarthritic changes in both knees and a bowed
In this patient which one of the following investigations would
help in identifying the cause of his condition?
Prostate specific antigen