In the USA, an ultrasound of the ovaries is not required to make a diagnosis of PCOS. Instead, a diagnosis can be made clinically from features of hyperandrogenism and ovulatory dysfunction.
In the UK, the diagnosis is made using imaging and blood tests. The imaging is performed using an ultrasound probe to detect evidence of the cysts (follicles). A blood test is also performed to show elevated serum concentrations of testosterone and serum LH, and decreased levels of sex hormone binding globulin (SHBG). Other investigations include serum dehydroepiandrosterone sulphate (DHAS) - elevated in adrenal disease, 17-hydroxyprogesterone (17-OHP) - elevated in congenital adrenal hyperplasia, and a 24hour urinary free cortisol - if cushing's syndrome is suspected.
Investigations may also be performed to exclude other conditions depending on the presenting symptoms. Other causes of disorders of ovulation are excluded by checking thyroid function, serum concentrations of prolactin and FSH.