Companies across the world are racing to sell diagnostic tests for endometriosis based on saliva or electroviscerography, with one Australian expert offering cautious optimism that the non-invasive tests have promise.

While transvaginal ultrasound and MRI are increasingly helping, laparoscopy remains the definitive way to diagnose endometriosis and patients still face notoriously long waits for diagnosis — often up to eight years, research suggests.

Last month, the NHS in England and Wales started offering two non-invasive tests in primary care as part of a three-year trial to assess them.

They include Endotest, which analyses self-collected saliva samples for 109 microRNA proteins associated with endometriosis.