Blood tests that show changes in the pregnancy hormones - human chorionic gonadotrophin (hCG) - are also usually done.

http://www.patient.co.uk/health/ectopic-pregnancy-leaflet

How is ectopic pregnancy confirmed?

If you have symptoms that may indicate an ectopic pregnancy you will usually be seen in the hospital immediately.

• A urine test can confirm that you are pregnant.
• An ultrasound scan may confirm an ectopic pregnancy. This is usually an internal (transvaginal) scan which is not painful and shows good views of the Fallopian tubes. However, the scan may not be clear if the pregnancy is very early. If this is the case, then a repeat scan a few days later is often done.
• Blood tests that show changes in the pregnancy hormones - human chorionic gonadotrophin (hCG) - are also usually done.