Occult Blood, faeces
Oestradiol (E2)
Oestriol
Oestrone
OGTT
OKT3 Antibodies
Oligoclonal bands
Opiate screen - urine
Oral Dexamethasone suppression test
Oral Glucose Tolerance Test
Osmolality - serum *
Osmolality - urine *
Osmotic Fragility
Ostase
Osteocalcin
O. tsutsugamushi Serology
Ova, cysts and parasites
Ovarian Antibodies
Ovarian Cyst fluid cytology
Oxalate - urine
Oxazepam
Oxygen Saturation of Haemoglobin
Oxypurinol