A new saliva-based test for endometriosis is being trialled in the United Kingdom, raising hopes that the condition could eventually be detected without invasive procedures.
The test is one of two non-invasive methods currently being studied over the next three years. The other examines electrical activity in the gut, with researchers assessing whether both approaches can help doctors identify endometriosis much earlier in patients attending general practices.
Endometriosis occurs when tissue similar to the lining of the uterus grows outside the uterus. It can cause severe period and pelvic pain, discomfort during intercourse, bowel and bladder problems, as well as difficulties becoming pregnant.
However, diagnosing the condition can be challenging. Doctors usually rely on a combination of symptoms, physical examinations and imaging, while ultrasound and MRI may require specially trained professionals. A normal scan also does not necessarily rule out endometriosis, meaning some patients may eventually require laparoscopy, a surgical procedure involving a small camera inserted into the abdomen.
Known as Endotest, the saliva test examines tiny molecules called microRNAs, which are involved in regulating gene activity. Certain patterns may indicate the presence of endometriosis, with a French study involving 971 patients reporting high accuracy.
Despite the encouraging findings, researchers stressed that most participants in that study already had endometriosis. This differs from a typical general practice setting, where patients may have pelvic pain caused by a range of conditions involving the bowel, bladder or muscles.
The second test, EndoSure, works differently by measuring electrical signals from the gut through sensor pads placed on the abdomen. The procedure takes about 45 minutes and can be carried out at a GP surgery or specialist clinic.
An earlier study involving 154 women reported 95% sensitivity and 96% specificity. However, researchers noted limitations in the evidence, including the fact that many people in the control groups had not undergone surgery to definitively confirm they were free from endometriosis.
More recent preliminary findings presented at a scientific meeting also raised concerns. While EndoSure detected all cases of endometriosis in a small group of women, its reported specificity was only 5%, meaning the vast majority of people without the condition also produced a positive result.
Other non-invasive approaches are also being developed, including blood tests. These include EndomTest in the United States, PromarkerEndo in Australia and DotEndo, which examines microRNAs in blood.
Experts stressed that impressive accuracy figures should always be viewed in context, particularly because a diagnostic test needs to work reliably among the types of patients who would actually use it.
Even if these new tests eventually prove useful, imaging would still be important to determine where endometriosis is located and how extensive it is. Doctors would also need to assess adhesions, which are scar-like tissues that can cause pelvic organs to stick together.
For patients, an earlier diagnosis could potentially mean faster access to specialist care and treatment. However, researchers cautioned that a negative test should not automatically rule out endometriosis, particularly when symptoms persist.
The findings underline the potential of non-invasive testing, but larger and independent studies will be needed before such tests can be considered reliable tools for widespread clinical use.
