Monday June 28 2010
A woman's fertility starts to decline long before menopause
A blood test to predict when menopause will occur “could close the baby gap” by telling women how long they will remain fertile, reported The Guardian. Several other newspapers have reported on the hormone-based menopause test, saying that home testing kits could be available in a few years.
The news story is based on a study that has been presented at fertility conference but has not yet been published, meaning it is difficult to assess the methods and quality of this research. However, the limited information available suggested the study was small and relatively short, and further testing will be needed.
It is important to stress that a woman’s fertility level and ability to conceive start to decline long before her periods stop and, therefore, a test predicting menopause may be of limited value in this area. Also, fertility levels can be affected by other factors, such as the quality of a man’s sperm or blocked ovarian tubes in the woman. The test may have a role in predicting early menopause, although further results are needed to confirm this.
Where did the story come from?
News reports about this test are based on a press release and conference abstract presented at the 2010 conference of the European Society of Human Reproduction and Embryology.
These documents present only limited details of a study carried out by researchers from Shaheed Beheshti University of Medical Sciences in Iran. No information is available as to if or when the research may be published in a peer-reviewed journal, or about how the research was funded.
The results presented in the press release were reported accurately, if uncritically, by most newspapers. Most papers also published comments from independent experts, who set the research in context and addressed the fact that such a test is only of limited use to most women because fertility levels start to fall well before the menopause occurs. The Daily Mail said that a home testing kit could be on sale within three years, but it is unclear on what this prediction is based.
None of the reports pointed out that their information was based on a conference abstract and press release and that the full results have not yet been published.
What kind of research was this?
This particular piece of research aimed to test a statistical model developed to accurately predict the age at which the menopause would occur. The model is based on assessing levels of a hormone called anti-mullerian hormone (AMH), which is produced by the ovaries. AMH controls the development of ovarian follicles from which eggs develop, and some experts have suggested it could be a marker for ovarian function. The researchers wanted to test whether measuring AMH at various ages could predict when women would reach the menopause.
What did the research involve?
There is only limited information available on the methods used in this research. However according to the abstract and press release, the researchers took blood samples to measure blood levels of AMH in 266 women, aged 20-49, randomly selected from a larger, prospective cohort study called the Tehran Lipid and Glucose Study. This ongoing study aims to identify cardiovascular risk factors among the Iranian population.
In this smaller study, the researchers measured AMH levels twice more, at three-yearly intervals. They also collected information on the women’s reproductive background and reproductive history. They then developed and tested a statistical model for estimating the women’s age at menopause using a single measurement of AMH in blood samples.
What were the basic results?
Information on the results is also limited but the researchers say they found a “high degree of correlation” between the estimated ages at menopause provided by their formula model and the actual age at menopause seen in a subgroup of 63 women who reached menopause during the study. The average difference between the predicted age using the model and the women’s actual age was only a third of a year and the maximum margin of error of three to four years.
Using this statistical model, the researchers say they were able to identify the specific AMH levels at different ages (20, 25 and 30 years) that would predict if women were likely to have an early menopause (before 45) or reach menopause over 50 years. Among the group studied, the average age at the menopause was 52 years.
How did the researchers interpret the results?
The researchers say their study suggests that the AMH can be used to precisely forecast the age at menopause, even in young women. Larger studies that follow women in their 20s for several years are needed to validate the accuracy of the measurements, they add.
This was a small study carried out over a limited period (about six years), which tested whether levels of AMH in women of reproductive age could be used to predict the age they will reach the menopause. It seems to have been designed with a reasonable cut-off point set for the test, the first step in preparing a potential test for clinical use. Since the study has not been published yet, it is not possible to give detailed information about its methods or results. However, if validated by further studies, such a test could be particularly useful in predicting early menopause, giving women who may experience it time to plan their future.
The fact that so far only 63 women actually reached menopause in the study and only three of them were under 45, means the mathematical formula has only undergone limited testing. It should be stressed that until there are larger studies following women from the age of 20 to the age they actually reach menopause, the method the researchers used has not been proven.
As with all studies assessing a diagnostic test, it will be important to follow up this initial study with others, setting a cut-off point that can establish the sensitivity and specificity of the test. What is needed are statistical measures that relate to the number of women correctly identified by the test as going on to an early menopause (or late menopause) and also the number of women incorrectly identified or predicted as heading for early or late menopause when they do not. These results, when published, will help decide the true value of the test.