Wednesday August 19 2009
The bright area is a build up of tissue outside the womb
There is now a "rapid test to diagnose the common womb condition of endometriosis", the Daily Mail has reported. A quick tissue sample can be taken while the woman is awake, avoiding the need for surgery under a general anaesthetic, the Daily Mail article on the endometriosis test says.
This well-conducted study has demonstrated that it may be possible to make a diagnosis of endometriosis through biopsy samples taken from the lining of the womb. This study found the new test to be highly accurate in identifying women with endometriosis, picking up 98% of women detected using the standard surgical method. It had slightly lower accuracy in correctly providing a negative test result in women who definitely did not have the condition, meaning that there is less confidence in positive test results.
As the authors say, this was a pilot study and the results would need to be verified in a much larger sample of women. Whether the predictive accuracy of this test is acceptable would also need to be considered. In addition, before it could be introduced, consideration would need to be given to the resources that would be required to implement this test, where the test would be available (for example, in gynaecological clinics) and which women would be eligible for the test.
Where did the story come from?
Moamar Al-Jefout and colleagues of the University of Sydney, Australia, and Mutah University, Jordan, carried out this research. The study was funded by the Department of Obstetrics and Gynaecology of the University of Sydney. It was published in the peer-reviewed medical journal Human Reproduction.
What kind of scientific study was this?
Endometriosis is a fairly common and troublesome gynaecological condition in which the lining of the uterus is found in other locations in the pelvis and abdomen, causing chronic pelvic pain and often difficulty conceiving. This study compared a potential new method of diagnosing endometriosis to a standard method of diagnosis used in clinical practice.
The current gold-standard method of diagnosis is performed under general anaesthetic using a type of keyhole surgery called a laparoscopy. In this diagnostic study the researchers compared the efficacy of a new, simpler test in which a biopsy (tissue sample) from the endometrium (the lining of the uterus) is taken via the vagina and then examined for the presence of nerve fibres. Prior reports have noted that in some women diagnosed with endometriosis small sensory nerve fibres have been detected in the functional layer of the endometrium (the layer adjacent to the uterine cavity which changes throughout the menstrual cycle).
The study recruited a total of 103 women (average 34 years) who were scheduled to undergo investigation for chronic pelvic pain and/or infertility. Prior to the standard method of diagnostic laparoscopy the researchers took an endometrial biopsy through the vagina using a device called the Endosampler.
The presence of nerve fibres in the biopsy sample was then assessed in the laboratory by two histologists. Satisfactory biopsies were obtained from 99 of the 103 women in the total study set. A separate histologist assessed the tissue samples obtained through laparoscopy.
What were the results of the study?
In the 99 women who completed the study, laparoscopy (the gold standard) provided 64 diagnoses of endometriosis of variable degrees of severity. The experimental biopsy method detected nerve fibres in 63 of these 64 women.
Of the 35 women who did not have endometriosis according to laparoscopy, the new method detected no nerve fibres in the functional layers of 29 women, while in six women there were nerve fibres present. These six women had significantly greater nerve fibre density (3.1 per mm2) than those with endometriosis identified through laparoscopy (2.7 per mm2). Women with both endometriosis and pain symptoms had significantly higher nerve fibre density compared to women with infertility but no pain.
The researchers calculated that for diagnosing endometriosis through the detection of nerve fibres obtained at biopsy:
- Sensitivity (accurately identifying a positive sample) was 98%.
- The specificity (accurately identifying a negative sample) was 83%.
- The positive predictive value (proportion of people with a positive test result who are correctly diagnosed as positive) was 91%.
- The negative predictive value (proportion with a negative test result who are correctly diagnosed as negative) was 96%.
What interpretations did the researchers draw from these results?
The authors conclude that the use of endometrial biopsy with detection of nerve fibres provides a reliable method of diagnosing endometriosis that offers levels of accuracy close to those of diagnosis through laparoscopic assessment.
What does the NHS Knowledge Service make of this study?
This well conducted study has demonstrated that it may be possible to make a diagnosis of endometriosis through endometrial biopsy. If this method proves viable it would potentially avoid the need for invasive surgery and anaesthesia, and help to reduce the often substantial delay that many women experience between first having symptoms and receiving a definite diagnosis. However, as the authors say, the results of this pilot study would need to be verified in a larger sample of women.
This study found the test to be highly accurate in positively identifying women who had endometriosis, but to have slightly lower accuracy in correctly excluding endometriosis in women who did not have a diagnosis of the condition. According to laparoscopy, six women without endometriosis also had detectable nerve fibres, meaning less confidence in a positive test result.
These findings would need to be compared to those obtained in other samples, and then consideration would need to be given to whether these predictive figures were acceptable. In addition, before this test could be brought into practice, consideration would need to be given to the resources that would be required to implement this test, where the test would be available (for example, in gynaecological clinics) and which women would be eligible for the test.