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The prevalence and phenotypic features of polycystic ovary syndrome: a systematic review and meta-analysis.

STUDY QUESTION
What is the reported overall prevalence of polycystic ovary syndrome (PCOS) according to the criteria of the National Institutes of Health (NIH), Rotterdam or the Androgen Excess and PCOS Society (AE-PCOS Society)?


SUMMARY ANSWER
The reported overall prevalence of PCOS (95% CI) according to diagnostic criteria of the NIH, Rotterdam and the AE-PCOS Society is 6% (5-8%, n = 18 trials), 10% (8-13%, n = 15 trials) and 10% (7-13%, n = 10 trials), respectively.


WHAT IS ALREADY KNOWN
PCOS is the most common endocrine disorder among women of reproductive age. Although many studies have investigated the prevalence of PCOS, there are discrepancies in their results, in part due to the use of various definitions of the syndrome and its subphenotypes, differences between study cohorts, ethnicities, and types of recruitment and sampling.


STUDY DESIGN, SIZE, DURATION
A systematic review and meta-analysis were performed on all published studies that have reported the prevalence of PCOS according to at least one subset of diagnostic criteria.


PARTICIPANTS/MATERIALS, SETTING, METHODS
To identify relevant studies based on the PRISMA statement, PubMed and Ovid databases were searched up to September 2015 by two blind investigators using the terms 'PCOS', 'polycystic ovarian disease', 'Stein Leventhal syndrome', 'Androgen Excess Society', 'National Institute of Health', 'Rotterdam', 'ESHRE/ASRM', 'criteria' and 'prevalence'. Articles that represented the prevalence of PCOS according to at least one subset of diagnostic criteria were included. Exclusion criteria were a focus on adolescent subjects, an absence of data on prevalence, inappropriate design or non-English reporting. An appraisal tool to evaluate the methodological quality of the available studies was generated by the authors.


MAIN RESULTS AND THE ROLE OF CHANCE
A total of 55 reports remained following screening of the abstracts and text for the subject of the study. Of these, 24 articles were eligible and evaluated for qualitative and quantitative synthesis. Since heterogeneity was observed among studies, a random-effects model was used to estimate the prevalence and its 95% CI. The proportions of PCOS prevalence (95% CI) according to the diagnostic criteria of NIH, Rotterdam and AE-PCOS Society were 6% (5-8%, n = 18 trials), 10% (8-13%, n = 15 trials) and 10% (7-13%, n = 10 trials), respectively. When only unselected population studies were included, the given rates were 6% (5-8%, n = 3 trials), 9% (7-12%, n = 6 trials) and 10% (7-14%, n = 3 trials). The respective proportions for hirsutism, hyperandrogenaemia, polycystic ovaries (PCO) and oligo-anovulation were 13% (8-20%, n = 14 trials), 11% (8-15%, n = 9 trials), 28% (22-35%, n = 12 trials) and 15% (12-18%, n = 19 trials), respectively.


LIMITATIONS, REASONS FOR CAUTION
The effects of ethnic differences, particularly, on the presence or severity of hirsutism cannot be ruled out in any way. In addition, there was a lack of standardization in defining phenotypes of the syndrome and selection bias was evident in most of the studies regarding recruitment of the cohorts.


WIDER IMPLICATIONS OF THE FINDINGS
Geographical differences in frequencies of the components of the syndrome, such as oligo-anovulation and clinical/biochemical androgen excess, must be taken into account in the development and implementation of regional diagnostic and precision treatment strategies. Further efforts and resources are required to increase standardization of the methods and comparability of the study results on prevalence and phenotypic characterization of PCOS around the globe.


STUDY FUNDING/COMPETING INTERESTS
No funding to declare. The authors have no conflicts of interest to declare.


REGISTRATION NUMBER
None.