For many women, getting a diagnosis of endometriosis can be a long and frustrating process – recent Endometriosis UK data published in March 2026 puts the UK average at 9 years and 4 months. Symptoms may be significant, yet examinations and ultrasound scans can be normal. Until recently, there has also been no simple blood or saliva test that could reliably help identify the condition.
But that may be beginning to change!
A new non-invasive test called Ziwig Endotest® uses a saliva sample to look for a molecular pattern associated with endometriosis. The technology has produced very encouraging results in clinical studies and is currently being assessed by the National Institute for Health and Care Excellence (NICE) for early use within the NHS.
So, the question is: what exactly is this new saliva test for endometriosis? How can endometriosis be detected in saliva, how accurate is Endotest, and where might it fit into the investigation of women with suspected endometriosis?
What is endometriosis?
Endometriosis is a chronic condition in which endometrial tissue (similar to the lining of the womb) is found elsewhere in the body, most commonly within the pelvis.
It can cause devastating symptoms including:
- very painful periods (dysmenorrhoea)
- chronic or cyclical pelvic pain
- pain before, during or after sex
- pain when opening the bowels
- cyclical bowel symptoms
- pain passing urine and increased bladder irritability
- cyclical rectal bleeding or blood in the urine
- fertility difficulties
- fatigue
Importantly, the severity of a woman’s symptoms does not necessarily correspond to the extent of her endometriosis.
Endometriosis symptoms can also overlap with other gynaecological and hormone-related conditions. This is one reason why taking a detailed history – including exactly when symptoms occur in relation to the menstrual cycle – can be so helpful.
For example, women experiencing predominantly severe cyclical mood, anxiety, irritability or behavioural symptoms may need assessment for Premenstrual Dysphoric Disorder (PMDD) rather than, or sometimes alongside, investigation of physical symptoms.
PMDD and endometriosis are very different conditions, but both demonstrate why the timing and pattern of symptoms throughout the menstrual cycle can provide important diagnostic information.
Why can endometriosis be difficult to diagnose?
One of the major difficulties with endometriosis is that there hasn’t traditionally been one simple test that can reliably confirm or exclude it.
Assessment starts with listening carefully to the symptoms. Depending upon the clinical picture, this may then involve examination, pelvic ultrasound and sometimes MRI.
Ultrasound is extremely useful for identifying ovarian endometriomas and some forms of deep endometriosis. However, a normal ultrasound does not exclude endometriosis.
This is an important point. A woman can have significant symptoms and still have a normal scan.
NICE specifically advises clinicians not to exclude endometriosis simply because the pelvic examination and ultrasound are normal.
Historically, laparoscopy – keyhole surgery allowing direct visualisation of the pelvis – has therefore played an important role in diagnosis. Although laparoscopy can also allow treatment at the same time, it is an invasive surgical procedure and clearly isn’t an ideal diagnostic test for every woman with possible endometriosis. It can also cause scarring, adhesions and worsening of symptoms in the long run.
This is why the development of an accurate, non-invasive biological test has generated so much interest.
What is the new saliva test for endometriosis?
Ziwig Endotest® is an in-vitro diagnostic test designed to help diagnose endometriosis using a sample of saliva.
Rather than looking for one particular hormone or protein, Endotest analyses tiny molecules called microRNAs, or miRNAs.
MicroRNAs are very small RNA molecules involved in regulating gene expression. Researchers have discovered that different diseases can be associated with characteristic patterns of microRNA expression.
Research into endometriosis has identified a particular combination of salivary microRNAs associated with the condition.
Endotest analyses a signature of 109 different microRNAs.
The laboratory uses sophisticated molecular technology called next-generation sequencing (NGS) to analyse these molecules. An algorithm using artificial intelligence then interprets the complex pattern.
Put more simply, Endotest isn’t looking for one abnormal hormone level; it is looking for a complex molecular “fingerprint” within the saliva and assessing whether that fingerprint is consistent with endometriosis.
How is the Endotest saliva test performed?
One of the most appealing aspects of Endotest is how straightforward the sample itself is to collect.
There is:
No blood test.
No internal examination.
No anaesthetic.
No surgical procedure.
The patient simply provides a saliva sample using a dedicated Endotest collection kit.
There are specific instructions that need to be followed carefully to avoid contaminating the sample. For example, food, drink, toothpaste, lipstick, tobacco and chewing gum can interfere with saliva collection.
The sample can be collected under the supervision of a healthcare professional or, where appropriate, self-collected by the patient.
The saliva sample is then sent to the laboratory for molecular analysis.
In the UK, The Doctors Laboratory (TDL) provides Ziwig Endotest testing. Their information page provides further details about the test, eligibility and the saliva collection process.
The test needs to be requested by a doctor, with the result returned to them for clinical interpretation.
Can Endotest be done while taking the contraceptive pill or other hormones?
Yes!
According to the manufacturer’s current information, Endotest can be performed while a woman is taking hormonal treatment and does not need to be timed to a particular point in the menstrual cycle.
This is potentially quite useful clinically, as many women being investigated for endometriosis are already using hormonal contraception or hormonal treatment to try to control their symptoms.
What happens to the saliva in the laboratory?
Now this is where a very simple sample meets some remarkably sophisticated science!
RNA is extracted from the saliva and the laboratory uses next-generation sequencing to examine the microRNAs present.
The expression pattern of the selected 109 microRNAs is then analysed using the Endotest algorithm. The result indicates whether the molecular signature is positive or negative for endometriosis.
However, there is something very important that Endotest cannot tell us – It does not show where the endometriosis is or how extensive it is.
Imaging and specialist assessment may therefore still be necessary, particularly if deep endometriosis, ovarian endometriomas or disease affecting the bowel, bladder or urinary tract is suspected, or if surgery is being considered.
How accurate is the Endotest for endometriosis?
This is where the research becomes particularly interesting.
A large study published in NEJM Evidence looked at 971 women aged 18–43 who had symptoms that could suggest endometriosis.
The results were very encouraging. The saliva test correctly identified around 97% of women who had endometriosis and correctly identified around 94% of women who did not have it.
Overall, the test gave the correct result in around 97 out of every 100 women in the study.
These are impressive results for a test that simply requires a saliva sample right? However, it is important to remember that the women in this study already had symptoms suggestive of endometriosis which therefore skews the resuls a little; so these figures do not mean that the test will be 97% accurate in every woman who takes it.
In other words, Endotest looks extremely promising, but it should be interpreted as part of a proper medical assessment rather than as a standalone screening test.
Has NICE approved the new endometriosis saliva test?
You may have seen headlines suggesting that the new endometriosis tests have been “approved by the NHS”, but the situation is a little more complicated than that.
In 2026, NICE began assessing new, less invasive ways of diagnosing endometriosis, including the Endotest saliva test. Endotest is being considered through NICE’s early-use assessment programme. This allows promising new technologies to be used while more evidence is collected about how well they work in everyday clinical practice. So, although this is a really positive step, it doesn’t mean that Endotest has simply been approved as a routine NHS test for everyone with possible endometriosis.
You can read more about how endometriosis is currently investigated and diagnosed in the NICE guidance on endometriosis: diagnosis and management.
The Royal College of Obstetricians and Gynaecologists (RCOG) has also published a clinical statement about these new diagnostic tests. They recognise how promising this technology could be, while also highlighting the need for further independent research.
I think this is an important balance. A simple, non-invasive test that could help women reach a diagnosis sooner would be a very welcome development – particularly when we know how long diagnosis can currently take. But, as with any new medical test, we also need to be confident that it performs just as well in everyday clinical practice as it has in research studies.
Who might benefit from a saliva test for endometriosis?
Endotest is currently indicated for symptomatic female patients aged 18–43 years who are clinically suspected of having endometriosis.
Symptoms that might raise suspicion include:
- significant or worsening period pain
- persistent or cyclical pelvic pain
- deep pain during or after intercourse
- cyclical bowel pain
- pain opening the bowels during menstruation
- cyclical urinary symptoms
- unexplained fertility difficulties
- a combination of symptoms strongly suggestive of endometriosis despite normal or inconclusive imaging.
It is not intended as a general screening test for women without symptoms.
According to current manufacturer and UK laboratory information, Endotest has not been validated for use during pregnancy, in women with a history of cancer or HIV, or outside the current 18–43-year age range.
It should also not be collected while someone has an acute infection.
Can you have endometriosis if your ultrasound is normal?
Yes. Absolutely.
This is perhaps one of the most important messages in this article, a normal pelvic ultrasound does not necessarily mean that there is no endometriosis.
NICE specifically advises that endometriosis should not be excluded simply because abdominal or pelvic examination and ultrasound are normal.
Specialist ultrasound can identify some forms of the disease very well, particularly ovarian endometriomas and deep endometriosis. However, superficial endometriosis may not be visible.
If symptoms remain strongly suggestive of endometriosis despite normal imaging, further assessment may therefore be appropriate.
This is precisely the type of diagnostic uncertainty in which non-invasive technologies such as Endotest could potentially prove particularly valuable.
What about bloating and bowel symptoms?
Bloating is very common and certainly doesn’t automatically mean that someone has endometriosis.
However, some women with endometriosis experience significant gastrointestinal symptoms, including bloating, constipation, diarrhoea and pain opening their bowels. A particularly useful clue can be whether these symptoms become predictably worse around menstruation.
There are many other causes of gastrointestinal symptoms, and hormones themselves can influence gut function.
For example, I have written separately about oestrogen deficiency and gut symptoms during menopause and about the estrobolome – the relationship between our gut microbiome and oestrogen metabolism.
The important point is that symptoms need to be considered together rather than assuming that bloating, bowel symptoms or pelvic discomfort must have one particular cause.
Does a positive Endotest mean I definitely have endometriosis?
Not necessarily. Although Endotest has shown very encouraging results in studies, no test should be looked at completely on its own.
A positive result makes endometriosis more likely, but your doctor will also consider your symptoms, medical history, examination and any previous scans or investigations.
The same applies to a negative result. Endotest appears to be very good at identifying women with endometriosis, but if your symptoms strongly suggest the condition, a negative test doesn’t necessarily mean that further investigation should stop.
This is why I think Endotest is most useful as part of a proper medical assessment. The test provides another valuable piece of information to help build the overall picture and decide what should happen next.
Does Endotest replace ultrasound, MRI or laparoscopy?
No, and this is very important to understand. These investigations provide different information.
- Endotest looks for a molecular signature associated with endometriosis.
- Ultrasound and MRI look for structural evidence of disease and can help establish its location and extent.
- Laparoscopy allows direct visualisation of the pelvis and, where appropriate, surgical treatment.
A saliva test cannot tell a surgeon where endometriosis is situated or whether the bowel, bladder, ovaries or other structures are affected.
The exciting possibility is that Endotest could provide another piece of information to help clinicians decide how likely endometriosis is and which patients may benefit from further specialist investigation or treatment.
What is EndoSure?
Endotest isn’t the only new technology currently being considered.
Another is called EndoSure.
Rather than analysing saliva, EndoSure uses adhesive sensors placed on the abdomen to measure gastrointestinal electrical activity – a technique known as electroviscerography.
The theory is that endometriosis may produce a characteristic pattern of gastrointestinal electrical activity.
However, the evidence base for EndoSure is currently less mature. The RCOG has described the technology as experimental at this stage and advises caution while larger independent studies establish how accurately it performs in routine clinical practice.
Why could this new technology be so important?
Perhaps the most exciting aspect of Endotest isn’t simply that it is a saliva test.
It is what it could potentially mean for women experiencing years of unexplained symptoms.
Someone with debilitating period pain, deep dyspareunia and cyclical bowel symptoms may undergo examinations and an ultrasound only to be told that everything appears normal.
But a normal scan does not necessarily mean that nothing is wrong.
Having another non-invasive piece of diagnostic information could help clinicians decide whether endometriosis is likely, whether treatment should be considered and whether referral for specialist assessment is appropriate.
If future independent studies reproduce the impressive results seen so far, molecular tests such as Endotest could become an important part of the way we investigate suspected endometriosis.
Endometriosis, PMDD and understanding cyclical symptoms
One of the reasons I am particularly interested in this area of women’s health is that the pattern of symptoms can often tell us as much as an isolated test result.
Endometriosis predominantly produces physical symptoms such as pelvic pain, dysmenorrhoea, dyspareunia and bowel or bladder symptoms.
PMDD, by contrast, predominantly causes severe cyclical psychological, emotional and cognitive symptoms during the luteal phase of the menstrual cycle.
If mood symptoms rather than pelvic pain are the major problem, you may find my articles on understanding the symptoms of PMDD and how suppressing the menstrual cycle can be used to treat PMDD useful.
Different conditions require different investigations and treatments, which is why establishing exactly what happens, when it happens and how it relates to the menstrual cycle is such an important part of women’s health assessment.
The important message
A simple saliva test that could help identify endometriosis is a really exciting development, particularly when we know that women can currently wait many years for a diagnosis.
The research into Endotest so far is very encouraging. In a large study of women with symptoms suggestive of endometriosis, the test correctly identified around 97% of women who had the condition and around 94% of those who did not.
However, Endotest is still relatively new and we need more independent research to see how well it performs when used more widely in everyday healthcare.
Most importantly, a test should never replace listening to the patient. Understanding a woman’s symptoms, when they occur, how they relate to her menstrual cycle and what impact they are having on her life is still at the heart of making the right diagnosis.
For women who have spent years living with pain or other symptoms despite scans and investigations appearing “normal”, having access to a simple, non-invasive test that could provide another piece of the puzzle is a very welcome step forward.
Further information
For more information about the test itself and how samples are processed in the UK, visit The Doctors Laboratory – Ziwig Endotest.
You can also read the NICE guidance on the diagnosis and management of endometriosis and the RCOG patient information about endometriosis.
References
- Bendifallah S, Roman H, Suisse S, et al. Validation of a Saliva Micro-RNA Signature for Endometriosis. NEJM Evidence. 2025;4(11).
- Bendifallah S, Dabi Y, Suisse S, et al. Validation of the Salivary miRNA Signature of Endometriosis – Interim Data. NEJM Evidence. 2023;2(7).
- National Institute for Health and Care Excellence (NICE). Endometriosis: diagnosis and management. NG73. Updated 2024.
- National Institute for Health and Care Excellence (NICE). Technologies for the rapid diagnosis of endometriosis – early use assessment. 2026.
- Royal College of Obstetricians and Gynaecologists. Clinical statement on new diagnostic technologies for endometriosis in primary care. 2026.
- The Doctors Laboratory. Ziwig Endotest®.
- Ziwig. Ziwig Endotest® – scientific and technical information.
What is the new saliva test for endometriosis?
Ziwig Endotest® is a new, non-invasive test designed to help diagnose endometriosis using a simple saliva sample. It looks at 109 tiny molecules called microRNAs (miRNAs) that are naturally found in saliva. Research has shown that women with endometriosis appear to have a particular pattern, or “signature”, of these molecules. The laboratory analyses this pattern using sophisticated sequencing technology and an algorithm to see whether it matches the signature associated with endometriosis.
So, unlike an ultrasound or MRI, Endotest isn’t actually looking for areas of endometriosis. Instead, it is looking for a biological fingerprint that suggests the condition is present.
How accurate is the saliva test for endometriosis?
The results so far are very encouraging.
In a large study involving 971 women aged 18–43 with symptoms suggestive of endometriosis, the test correctly identified around 97% of women who had endometriosis and around 94% of women who did not. Overall, it gave the correct result in approximately 97 out of every 100 women in the study.
However, these women had already been selected because their symptoms suggested endometriosis, so we shouldn’t assume the test will perform in exactly the same way in everyone. Further independent research in everyday clinical settings will be important.
How is Endotest performed?
The test itself is very straightforward. You provide a saliva sample using a special Endotest collection kit. There is no blood test, internal examination, anaesthetic or surgical procedure involved. The sample is then sent to a specialist laboratory, where the microRNAs in the saliva are analysed.
In the UK, you can find more information about the test and the collection process from The Doctors Laboratory (TDL).
Do I need to stop the contraceptive pill or hormonal treatment before Endotest?
No. One of the useful things about Endotest is that it can be performed while you are using hormonal treatments, including hormonal contraception. It also doesn’t need to be timed to a particular point in your menstrual cycle.
There are some simple instructions to follow before collecting your saliva – such as avoiding eating, drinking, smoking, chewing gum or brushing your teeth for a short period beforehand – to make sure the laboratory receives a good-quality sample.
Can I have endometriosis even if my ultrasound is normal?
Yes. A normal ultrasound does not rule out endometriosis.
Ultrasound can be very useful for finding ovarian endometriomas (endometriosis cysts) and some forms of deeper endometriosis, particularly when the scan is performed by someone experienced in looking for the condition. However, not all endometriosis can be seen on an ultrasound, in fact, NICE specifically advises doctors not to rule out endometriosis simply because an examination and ultrasound are normal.
So, if your symptoms strongly suggest endometriosis, it may still be appropriate to investigate further even if your scan hasn’t shown anything abnormal.
Can an MRI scan rule out endometriosis?
No. MRI can be very helpful, particularly if we are concerned about deeper endometriosis or want to understand where disease might be located. However, just like ultrasound, a normal MRI cannot completely rule out endometriosis.
If your symptoms are very suggestive of the condition, further assessment may still be appropriate despite normal imaging.
Does a positive Endotest mean I definitely have endometriosis?
Not necessarily. Although Endotest has shown very encouraging results in studies, no test should be looked at completely on its own. A positive result makes endometriosis more likely, but your doctor will also consider your symptoms, medical history, examination and any previous scans or investigations.
The result is therefore another important piece of information that can help build the overall picture and decide what should happen next.
Does a negative Endotest completely rule out endometriosis?
No test can give us absolute certainty.
Endotest appears to be very good at identifying women who have endometriosis, which means a negative result can be reassuring. However, if your symptoms still strongly suggest endometriosis, a negative test doesn’t necessarily mean that all further investigation should stop.
This is another reason why the result is best interpreted by a clinician who understands your symptoms and medical history.
Does Endotest tell me where my endometriosis is?
No. This is an important limitation of the test.
Endotest can tell us whether the biological signature associated with endometriosis has been detected, but it cannot tell us where the endometriosis is, how extensive it might be or whether organs such as the ovaries, bowel or bladder are involved.
For that reason, specialist ultrasound, MRI or sometimes laparoscopy may still be needed.
Does Endotest replace laparoscopy?
No. They provide different types of information. A laparoscopy is a surgical procedure that allows a surgeon to look directly inside the pelvis. If endometriosis is found, it may also be possible to treat it during the same procedure.
Endotest can’t do this. What it may be able to provide is useful additional evidence about whether endometriosis is likely, without putting someone through an invasive procedure simply to obtain that information. There will still be circumstances where laparoscopy is the appropriate next step, particularly if symptoms persist or surgical treatment is being considered.
How long does it usually take to be diagnosed with endometriosis?
Unfortunately, far too long. According to Endometriosis UK’s 2026 data, women in the UK are now waiting an average of around 9 years and 4 months from first seeking medical help to receiving a diagnosis of endometriosis. During that time, women may have repeated appointments and investigations without getting a clear explanation for their symptoms.
This is one of the reasons why the development of simpler, less invasive diagnostic tests is potentially so important.
What symptoms might suggest endometriosis?
Endometriosis can affect women very differently, but symptoms that might make us think about it include:
- very painful periods
- pelvic pain that persists or follows a cyclical pattern
- pain during or after sex
- pain opening your bowels, particularly around your period
- bowel symptoms that become worse around menstruation
- bladder symptoms that follow a similar cyclical pattern
- blood in the urine or rectal bleeding associated with menstruation
- difficulty becoming pregnant
- fatigue.
It is also worth remembering that the severity of your symptoms doesn’t necessarily tell us how much endometriosis you have. Some women with relatively small areas of disease can have significant symptoms, while others with more extensive endometriosis may experience surprisingly little pain.
Is Endotest suitable for everyone?
No. At present, Endotest is intended for women aged 18–43 who have symptoms that suggest endometriosis. It isn’t designed as a general screening test for women who don’t have symptoms. There are also some situations where the test hasn’t been validated or isn’t currently recommended, including during pregnancy and in people with certain medical conditions.
This is why I think it is important to have a medical assessment first, rather than simply ordering the test without considering whether it is appropriate for you.
Is Endotest available on the NHS?
You may have seen headlines suggesting that new endometriosis tests have been “approved by the NHS”, but the situation is a little more complicated than that. Presently NICE has been assessing Endotest and other new diagnostic technologies through its early-use assessment programme. This allows promising new technologies to be considered while further evidence is collected about how well they work in everyday healthcare.
This is a positive development, but it doesn’t mean that Endotest is currently available as a routine NHS test for everyone with suspected endometriosis.
NHS availability will depend on the final NICE recommendations and how the test is introduced into local services.
What happens if my Endotest result is positive?
There isn’t one automatic next step – it will depend on your symptoms, previous investigations and what you would like to do about them.
For some women, a positive result may provide enough additional evidence to have a conversation about medical treatment. For others, further imaging or referral to a gynaecologist or specialist endometriosis service may be appropriate. If there are symptoms that make us concerned about deeper endometriosis or possible involvement of the bowel, bladder or urinary tract, specialist assessment becomes particularly important.
Ultimately, the purpose of Endotest isn’t simply to give you a “positive” or “negative” answer. It is to provide another piece of information that can help you and your doctor make a better-informed decision about what to do next.
This article is intended for general information and education and does not replace an individual medical assessment, diagnosis or treatment.