What to expect when you are tested for PCOS. Because PCOS is a diagnosis of exclusion, the chapter starts with the conditions doctors rule out first, such as thyroid problems and raised prolactin. It then explains the three main steps in confirming a diagnosis: assessing symptoms, blood tests and a transvaginal ultrasound, including what the scan looks for and how the blood tests are grouped. It closes with practical advice on tracking your cycle and why working closely with your doctor matters, given how much the symptoms overlap with other conditions.