The Mystery of Piezophiles: Understudied Microorganisms from the Deep, Dark Subsurface.

Microorganisms that can withstand high pressure within an environment are termed piezophiles. These organisms are considered extremophiles and inhabit the deep marine or terrestrial subsurface. Because these microorganisms are not easily accessed and require expensive sampling methods and laboratory instruments, advancements in this field have been limited compared to other extremophiles. This review summarizes the current knowledge on piezophiles, notably the cellular and physiological adaptations that such microorganisms possess to withstand and grow in high-pressure environments. Based on existing studies, organisms from both the deep marine and terrestrial subsurface show similar adaptations to high pressure, including increased motility, an increase of unsaturated bonds within the cell membrane lipids, upregulation of heat shock proteins, and differential gene-regulation systems. Notably, more adaptations have been identified within the deep marine subsurface organisms due to the relative paucity of studies performed on deep terrestrial subsurface environments. Nevertheless, similar adaptations have been found within piezophiles from both systems, and therefore the microbial biogeography concepts used to assess microbial dispersal and explore if similar organisms can be found throughout deep terrestrial environments are also briefly discussed.

Biodegradation of Polymers Used in Oil and Gas Operations: Towards Enzyme Biotechnology Development and Field Application.

Linear and crosslinked polymers are commonly used in the oil and gas industry. Guar-derived polymers have been extensively utilized in hydraulic fracturing processes, and recently polyacrylamide and cellulose-based polymers have also found utility. As these polymers are used during various phases of the hydraulic fracturing process, they can accumulate at formation fracture faces, resulting in undesired filter cakes that impede oil and gas recovery. Although acids and chemical oxidizers are often added in the fracturing fluids to degrade or 'break' polymer filter cakes, the constant use of these chemicals can be hazardous and can result in formation damage and corrosion of infrastructure. Alternately, the use of enzymes is an attractive and environmentally friendly technology that can be used to treat polymer accumulations. While guar-linkage-specific enzyme breakers isolated from bacteria have been shown to successfully cleave guar-based polymers and decrease their molecular weight and viscosity at reservoir conditions, new enzymes that target a broader range of polymers currently used in hydraulic fracturing operations still require research and development for effective application. This review article describes the current state-of-knowledge on the mechanisms and enzymes involved in biodegradation of guar gum, polyacrylamide (and hydrolyzed polyacrylamide), and carboxymethyl cellulose polymers. In addition, advantages and challenges in the development and application of enzyme breaker technologies are discussed.

Preparation and identification of carboxymethyl cellulose-degrading enzyme candidates for oilfield applications.

Carboxymethyl cellulose (CMC) is often used during hydraulic fracturing (fracking) operations as a fluid viscosifier to facilitate proppant delivery. However, the accumulation of residual CMC at fracture faces can result in formation damage, thereby impeding oil and gas recovery. Whereas harsh chemical oxidizers are typically added to disrupt these polymer accumulations, there is now industrial interest in developing clean, biological approaches for the degradation of CMC under fracking conditions. Using a methanogenic culture known to utilize CMC under conditions typically found in oil fields, we developed an efficient method to isolate and purify CMC-degrading enzymes. Initial purification and concentration of cellular components produced an increase in exo-ß-(1,4)-exoglucanase and ß-(1,4)-glucosidase activities by 9-fold and 26-fold, respectively. Partially purified extracts provided substantial degradation of CMC as monitored by viscosity reduction within three hours at 50 °C, an improvement over the untreated cell-free extract which required 48 h to achieve similar viscosity values, outperforming a commercially-available cellulase preparation. Putative cellulases were identified within the isolated enzyme population, with endo-ß-(1,4)-xylanase from Caldicoprobacter faecalis hypothesized to be an important contributor to CMC degradation. This study demonstrates that enzyme technology holds great promise as a viable approach to degrade CMC accumulations under field conditions.

Metagenomic Investigation of a Low Diversity, High Salinity Offshore Oil Reservoir.

Oil reservoirs can represent extreme environments for microbial life due to low water availability, high salinity, high pressure and naturally occurring radionuclides. This study investigated the microbiome of saline formation water samples from a Gulf of Mexico oil reservoir. Metagenomic analysis and associated anaerobic enrichment cultures enabled investigations into metabolic potential for microbial activity and persistence in this environment given its high salinity (4.5%) and low nutrient availability. Preliminary 16S rRNA gene amplicon sequencing revealed very low microbial diversity. Accordingly, deep shotgun sequencing resulted in nine metagenome-assembled genomes (MAGs), including members of novel lineages QPJE01 (genus level) within the Halanaerobiaceae, and BM520 (family level) within the Bacteroidales. Genomes of the nine organisms included respiratory pathways such as nitrate reduction (in Arhodomonas, Flexistipes, Geotoga and Marinobacter MAGs) and thiosulfate reduction (in Arhodomonas, Flexistipes and Geotoga MAGs). Genomic evidence for adaptation to high salinity, withstanding radioactivity, and metal acquisition was also observed in different MAGs, possibly explaining their occurrence in this extreme habitat. Other metabolic features included the potential for quorum sensing and biofilm formation, and genes for forming endospores in some cases. Understanding the microbiomes of deep biosphere environments sheds light on the capabilities of uncultivated subsurface microorganisms and their potential roles in subsurface settings, including during oil recovery operations.

Enzyme biotechnology development for treating polymers in hydraulic fracturing operations.

Carboxymethyl cellulose (CMC) is a polymer used in many different industrial sectors. In the oil and gas industry, CMC is often used during hydraulic fracturing (fracking) operations as a thickening agent for effective proppant delivery. Accumulations of CMC at fracture faces (known as filter cakes) can impede oil and gas recovery. Although chemical oxidizers are added to disrupt these accumulations, there is industrial interest in developing alternative, enzyme-based treatments. Little is known about CMC biodegradation under fracking conditions. Here, we enriched a methanogenic CMC-degrading culture and demonstrated its ability to enzymatically utilize CMC under the conditions that typify oil fields. Using the extracellular enzyme fraction from the culture, significant CMC viscosity reduction was observed between 50 and 80˚C, at salinities up to 20% (w/v) and at pH 5-8 compared to controls. Similar levels of viscosity reduction by extracellular enzymes were observed under oxic and anoxic conditions. This proof-of-concept study demonstrates that enzyme biotechnology holds great promise as a viable approach to treating CMC filter cakes under oilfield conditions.

Combined Use of Diagnostic Fumarate Addition Metabolites and Genes Provides Evidence for Anaerobic Hydrocarbon Biodegradation in Contaminated Groundwater.

The widespread use of hydrocarbon-based fuels has led to the contamination of many natural environments due to accidental spills or leaks. While anaerobic microorganisms indigenous to many fuel-contaminated groundwater sites can play a role in site remediation (e.g., monitored natural attenuation, MNA) via hydrocarbon biodegradation, multiple lines of evidence in support of such bioremediation are required. In this study, we investigated two fuel-contaminated groundwater sites for their potential to be managed by MNA. Microbial community composition, biogeochemical indicators, fumarate addition metabolites, and genes diagnostic of both alkane and alkyl-monoaromatic hydrocarbon activation were assessed. Fumarate addition metabolites and catabolic genes were detected for both classes of hydrocarbon biodegradation at both sites, providing strong evidence for in situ anaerobic hydrocarbon biodegradation. However, relevant metabolites and genes did not consistently co-occur within all groundwater samples. Using newly designed mixtures of quantitative polymerase chain reaction (qPCR) primers to target diverse assA and bssA genes, we measured assA gene abundances ranging from 105-108 copies/L, and bssA gene abundances ranging from 105-1010 copies/L at the sites. Overall, this study demonstrates the value of investigating fuel-contaminated sites using both metabolites and genes diagnostic of anaerobic hydrocarbon biodegradation for different classes of hydrocarbons to help assess field sites for management by MNA.

Individualized versus standard FSH dosing in women starting IVF/ICSI: an RCT. Part 1: The predicted poor responder.

STUDY QUESTION: Does an increased FSH dose result in higher cumulative live birth rates in women with a predicted poor ovarian response, apparent from a low antral follicle count (AFC), scheduled for IVF or ICSI? SUMMARY ANSWER: In women with a predicted poor ovarian response (AFC < 11) undergoing IVF/ICSI, an increased FSH dose (225/450 IU/day) does not improve cumulative live birth rates as compared to a standard dose (150 IU/day). WHAT IS KNOWN ALREADY: In women scheduled for IVF/ICSI, an ovarian reserve test (ORT) can predict ovarian response to stimulation. The FSH starting dose is often adjusted based on the ORT from the belief that it will improve live birth rates. However, the existing RCTs on this topic, most of which show no benefit, are underpowered. STUDY DESIGN, SIZE, DURATION: Between May 2011 and May 2014, we performed an open-label multicentre RCT in women with an AFC < 11 (Dutch Trial Register NTR2657). The primary outcome was ongoing pregnancy achieved within 18 months after randomization and resulting in a live birth. We needed 300 women to assess whether an increased dose strategy would increase the cumulative live birth rate from 25 to 40% (two-sided alpha-error 0.05, power 80%). PARTICIPANTS/MATERIALS, SETTING, METHODS: Women with an AFC ≤ 7 were randomized to an FSH dose of 450 IU/day or 150 IU/day, and women with an AFC 8-10 were randomized to 225 IU or 150 IU/day. In the standard group, dose adjustment was allowed in subsequent cycles based on pre-specified criteria. Both effectiveness and cost-effectiveness of the strategies were evaluated from an intention-to-treat perspective. MAIN RESULTS AND THE ROLE OF CHANCE: In total, 511 women were randomized, 234 with an AFC ≤ 7 and 277 with an AFC 8-10. The cumulative live birth rate for increased versus standard dosing was 42.4% (106/250) versus 44.8% (117/261), respectively [relative risk (RR): 0.95 (95%CI, 0.78-1.15), P = 0.58]. As an increased dose strategy was more expensive [delta costs/woman: €1099 (95%CI, 562-1591)], standard FSH dosing was the dominant strategy in our economic analysis. LIMITATIONS, REASONS FOR CAUTION: Despite our training programme, the AFC might have suffered from inter-observer variation. As this open study permitted small dose adjustments between cycles, potential selective cancelling of cycles in women treated with 150 IU could have influenced the cumulative results. However, since first cycle live birth rates point in the same direction we consider it unlikely that the open design masked a potential benefit for the individualized strategy. WIDER IMPLICATIONS OF THE FINDINGS: Since an increased dose in women scheduled for IVF/ICSI with a predicted poor response (AFC < 11) does not improve live birth rates and is more expensive, we recommend using a standard dose of 150 IU/day in these women. STUDY FUNDING/COMPETING INTEREST(S): This study was funded by The Netherlands Organisation for Health Research and Development (ZonMW number 171102020). T.C.T., H.L.T. and S.C.O. received an unrestricted personal grant from Merck BV. H.R.V. receives monetary compensation as a member on an external advisory board for Ferring pharmaceutical BV. B.W.J.M. is supported by a NHMRC Practitioner Fellowship (GNT1082548) and reports consultancy for OvsEva, Merck and Guerbet. F.J.M.B. receives monetary compensation as a member of the external advisory board for Ferring pharmaceutics BV (the Netherlands) and Merck Serono (the Netherlands) for consultancy work for Gedeon Richter (Belgium) and Roche Diagnostics on automated AMH assay development (Switzerland) and for a research cooperation with Ansh Labs (USA). All other authors have nothing to declare. TRIAL REGISTRATION NUMBER: Registered at the ICMJE-recognized Dutch Trial Registry (www.trialregister.nl). Registration number NTR2657. TRIAL REGISTRATION DATE: 20 December 2010. DATE OF FIRST PATIENT'S ENROLMENT: 12 May 2011.

Hysteroscopy before in-vitro fertilisation (inSIGHT): a multicentre, randomised controlled trial.

BACKGROUND: Hysteroscopy is often done in infertile women starting in-vitro fertilisation (IVF) to improve their chance of having a baby. However, no data are available from randomised controlled trials to support this practice. We aimed to assess whether routine hysteroscopy before the first IVF treatment cycle increases the rate of livebirths. METHODS: We did a pragmatic, multicentre, randomised controlled trial in seven university hospitals and 15 large general hospitals in the Netherlands. Women with a normal transvaginal ultrasound of the uterine cavity and no previous hysteroscopy who were scheduled for their first IVF treatment were randomly assigned (1:1) to either hysteroscopy with treatment of detected intracavitary abnormalities before starting IVF (hysteroscopy group) or immediate start of the IVF treatment (immediate IVF group). Randomisation was done with web-based concealed allocation and was stratified by centre with variable block sizes. Participants, doctors, and outcome assessors were not masked to the assigned group. The primary outcome was ongoing pregnancy (detection of a fetal heartbeat at >12 weeks of gestation) within 18 months of randomisation and resulting in livebirth. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT01242852. FINDINGS: Between May 25, 2011, and Aug 27, 2013, we randomly assigned 750 women to receive either hysteroscopy (n=373) or immediate IVF (n=377). 209 (57%) of 369 women eligible for assessment in the hysteroscopy group and 200 (54%) of 373 in the immediate IVF group had a livebirth from a pregnancy during the trial period (relative risk 1·06, 95% CI 0·93-1·20; p=0·41). One (<1%) woman in the hysteroscopy group developed endometritis after hysteroscopy. INTERPRETATION: Routine hysteroscopy does not improve livebirth rates in infertile women with a normal transvaginal ultrasound of the uterine cavity scheduled for a first IVF treatment. Women with a normal transvaginal ultrasound should not be offered routine hysteroscopy. FUNDING: The Dutch Organisation for Health Research and Development (ZonMW).

IVF with planned single-embryo transfer versus IUI with ovarian stimulation in couples with unexplained subfertility: an economic analysis.

Couples with unexplained subfertility are often treated with intrauterine insemination (IUI) with ovarian stimulation, which carries the risk of multiple pregnancies. An explorative randomized controlled trial was performed comparing one cycle of IVF with elective single-embryo transfer (eSET) versus three cycles of IUI-ovarian stimulation in couples with unexplained subfertility and a poor prognosis for natural conception, to assess the economic burden of the treatment modalities. The main outcome measures were ongoing pregnancy rates and costs. This study randomly assigned 58 couples to IVF-eSET and 58 couples to IUI-ovarian stimulation. The ongoing pregnancy rates were 24% in with IVF-eSET versus 21% with IUI-ovarian stimulation, with two and three multiple pregnancies, respectively. The mean cost per included couple was significantly different: €2781 with IVF-eSET and €1876 with IUI-ovarian stimulation (P<0.01). The additional costs per ongoing pregnancy were €2456 for IVF-eSET. In couples with unexplained subfertility, one cycle of IVF-eSET cost an additional €900 per couple compared with three cycles of IUI-ovarian stimulation, for no increase in ongoing pregnancy rates or decrease in multiple pregnancies. When IVF-eSET results in higher ongoing pregnancy rates, IVF would be the preferred treatment. Couples that have been trying to conceive unsuccessfully are often treated with intrauterine insemination (IUI) and medication to improve egg production (ovarian stimulation). This treatment carries the risk of multiple pregnancies like twins. We performed an explorative study among those couples that had a poor prognosis for natural conception. One cycle of IVF with transfer of one selected embryo (elective single-embryo transfer, eSET) was compared with three cycles of IUI-ovarian stimulation. The aim of this study was to assess the economic burden of both treatments. The Main outcome measures were number of good pregnancies above 12weeks and costs. We randomly assigned 58 couples to IVF-eSET and 58 couples to IUI-ovarian stimulation. The ongoing pregnancy rates were comparable: 24% with IVF-eSET versus 21% with IUI-ovarian stimulation. There were two multiple pregnancies with IVF-eSET and three multiple pregnancies with IUI-ovarian stimulation. The mean cost per included couple was significantly different, €2781 with IVF-eSET and €1876 with IUI-ovarian stimulation. The additional costs per ongoing pregnancy were €2456 for IVF-eSET. In couples with unexplained subfertility, one cycle of IVF-eSET costed an additional €900 per couple compared to three cycles of IUI-ovarian stimulation, for no increase in ongoing pregnancy rates or decrease in multiple pregnancies. We conclude that IUI-ovarian stimulation is the preferred treatment to start with. When IVF-eSET results in a higher ongoing pregnancy rate (>38%), IVF would be the preferred treatment.

The OPTIMIST study: optimisation of cost effectiveness through individualised FSH stimulation dosages for IVF treatment. A randomised controlled trial.

BACKGROUND: Costs of in vitro fertilisation (IVF) are high, which is partly due to the use of follicle stimulating hormone (FSH). FSH is usually administered in a standard dose. However, due to differences in ovarian reserve between women, ovarian response also differs with potential negative consequences on pregnancy rates. A Markov decision-analytic model showed that FSH dose individualisation according to ovarian reserve is likely to be cost-effective in women who are eligible for IVF. However, this has never been confirmed in a large randomised controlled trial (RCT). The aim of the present study is to assess whether an individualised FSH dose regime based on an ovarian reserve test (ORT) is more cost-effective than a standard dose regime. METHODS/DESIGN: Multicentre RCT in subfertile women indicated for a first IVF or intracytoplasmic sperm injection cycle, who are aged < 44 years, have a regular menstrual cycle and no major abnormalities at transvaginal sonography. Women with polycystic ovary syndrome, endocrine or metabolic abnormalities and women undergoing IVF with oocyte donation, will not be included. Ovarian reserve will be assessed by measuring the antral follicle count. Women with a predicted poor response or hyperresponse will be randomised for a standard versus an individualised FSH regime (150 IU/day, 225-450 IU/day and 100 IU/day, respectively). Participants will undergo a maximum of three stimulation cycles during maximally 18 months. The primary study outcome is the cumulative ongoing pregnancy rate resulting in live birth achieved within 18 months after randomisation. Secondary outcomes are parameters for ovarian response, multiple pregnancies, number of cycles needed per live birth, total IU of FSH per stimulation cycle, and costs. All data will be analysed according to the intention-to-treat principle. Cost-effectiveness analysis will be performed to assess whether the health and associated economic benefits of individualised treatment of subfertile women outweigh the additional costs of an ORT. DISCUSSION: The results of this study will be integrated into a decision model that compares cost-effectiveness of the three dose-adjustment strategies to a standard dose strategy. The study outcomes will provide scientific foundation for national and international guidelines. TRIAL REGISTRATION: NTR2657.

The inSIGHT study: costs and effects of routine hysteroscopy prior to a first IVF treatment cycle. A randomised controlled trial.

BACKGROUND: In in vitro fertilization (IVF) and intracytoplasmatic sperm injection (ICSI) treatment a large drop is present between embryo transfer and occurrence of pregnancy. The implantation rate per embryo transferred is only 30%. Studies have shown that minor intrauterine abnormalities can be found in 11-45% of infertile women with a normal transvaginal sonography or hysterosalpingography. Two randomised controlled trials have indicated that detection and treatment of these abnormalities by office hysteroscopy after two failed IVF cycles leads to a 9-13% increase in pregnancy rate. Therefore, screening of all infertile women for intracavitary pathology prior to the start of IVF/ICSI is increasingly advocated. In absence of a scientific basis for such a policy, this study will assess the effects and costs of screening for and treatment of unsuspected intrauterine abnormalities by routine office hysteroscopy, with or without saline infusion sonography (SIS), prior to a first IVF/ICSI cycle. METHODS/DESIGN: Multicenter randomised controlled trial in asymptomatic subfertile women, indicated for a first IVF/ICSI treatment cycle, with normal findings at transvaginal sonography. Women with recurrent miscarriages, prior hysteroscopy treatment and intermenstrual blood loss will not be included. Participants will be randomised for a routine fertility work-up with additional (SIS and) hysteroscopy with on-the-spot-treatment of predefined intrauterine abnormalities versus the regular fertility work-up without additional diagnostic tests. The primary study outcome is the cumulative ongoing pregnancy rate resulting in live birth achieved within 18 months of IVF/ICSI treatment after randomisation. Secondary study outcome parameters are the cumulative implantation rate; cumulative miscarriage rate; patient preference and patient tolerance of a SIS and hysteroscopy procedure. All data will be analysed according to the intention-to-treat principle, using univariate and multivariate logistic regression and cox regression. Cost-effectiveness analysis will be performed to evaluate the costs of the additional tests as routine procedure. In total 700 patients will be included in this study. DISCUSSION: The results of this study will help to clarify the significance of hysteroscopy prior to IVF treatment. TRIAL REGISTRATION: NCT01242852.

Use of ovarian reserve tests for the prediction of ongoing pregnancy in couples with unexplained or mild male infertility.

The chance of infertile patients conceiving is related to factors like female age and duration of infertility. This prospective observational study evaluated whether the results of ovarian reserve tests, including the novel marker serum anti-Mullerian hormone (AMH), were of additional value in predicting ongoing pregnancy. Two hundred and twenty-two patients diagnosed with unexplained infertility or mild male factor (total motile count>10x10(6)) on the basis of the infertility work-up were prospectively included. Antral follicle count, AMH, inhibin B, FSH and oestradiol concentrations were determined during the early follicular phase. Outcome measures were treatment-dependent and treatment-independent ongoing pregnancy and time to ongoing pregnancy. There were 159 ongoing pregnancies, 52 of which occurred spontaneously. Pregnant patients were significantly younger than those who did not become pregnant (median age 32.4 versus 34.9 years, P<0.001) and FSH concentrations were higher in non-pregnant patients (median 6.8 versus 7.6 IU/l, P=0.04). Only age (hazard ratio 0.93, 95% CI 0.90-0.97) and whether or not the patient was undergoing treatment (hazard ratio 8.10, 95% CI 5.66-11.61) were significantly associated with time to ongoing pregnancy. Ovarian reserve tests, other than chronological age, seem of limited value in predicting (time to) ongoing pregnancy in patients with unexplained and mild male infertility.

Serum antimullerian hormone levels best reflect the reproductive decline with age in normal women with proven fertility: a longitudinal study.

OBJECTIVE: The aim of this study was to assess which of the basal ovarian reserve markers provides the best reflection of the changes occurring in ovarian function over time (i.e., reproductive aging). DESIGN: Prospective longitudinal study. SETTING: Healthy volunteers in an academic research center. PATIENT(S): Eighty-one women with normal reproductive performance during the course of their lives were longitudinally assessed. In this select group of women, becoming chronologically older was considered as a proxy variable for becoming older from a reproductive point of view. INTERVENTION(S): The women were assessed twice, with on average a 4-year interval (T(1) and T(2)). The number of antral follicles on ultrasound (AFC) and blood levels of antimullerian hormone (AMH), FSH, inhibin B, and E(2) were assessed. MAIN OUTCOME MEASURE(S): Longitudinal changes of the markers mentioned and the consistency of these parameters over time. RESULT(S): The mean ages at T(1) and T(2) were 39.6 and 43.6 years, respectively. Although AFC was strongly associated with age in a cross-sectional fashion, it did not change over time. The AMH, FSH, and inhibin B levels showed a significant change over time, in contrast to E(2) levels. The AMH and AFC were highly correlated with age both at T(1) and T(2), whereas FSH and inhibin B predominantly changed in women more than 40 years of age. To assess the consistency of these parameters over time, we investigated whether a woman's individual level above or below the mean of her age group at T(1) remained above or below the mean of her age group at T(2). Serum AMH concentrations showed the best consistency, with AFC as second best. The FSH and inhibin B showed only modest consistency, whereas E(2) showed no consistency at all. CONCLUSION(S): These results indicate that serum AMH represents the best endocrine marker to assess the age-related decline of reproductive capacity.

Anti-müllerian hormone is a promising predictor for the occurrence of the menopausal transition.

OBJECTIVE: Age at menopause and age at the start of the preceding period of cycle irregularity (menopausal transition) show considerable individual variation. In this study we explored several markers for their ability to predict the occurrence of the transition to menopause. DESIGN: A group of 81 normal women between 25 and 46 years of age visited the clinic two times (at T1 and T2) with an average interval of 4 years. All had a regular menstrual cycle pattern at T1. At T1, anti-mullerian hormone (AMH), follicle-stimulating hormone (FSH), inhibin B and estradiol (E2) were measured, and an antral follicle count (AFC) was made during the early follicular phase. At T2, information regarding cycle length and variability was obtained. Menopause transition was defined as a mean cycle length of less than 21 days or more than 35 days or as a mean cycle length of 21 to 35 days, but with the next cycle not predictable within 7 days during the last half year. A logistic regression analysis was performed, with the outcome measure as menopause transition. The area under the receiver operating curve (ROCAUC) was calculated as a measure of predictive accuracy. RESULTS: In 14 volunteers, the cycle had become irregular at T2. Compared with women with a regular cycle at T2, these women were significantly older (median 44.7 vs 39.8 y, P < 0.001) and differed significantly in AFC, AMH, FSH, and inhibin B levels assessed at T1. All parameters with the exception of E2 were significantly associated with the occurrence of cycle irregularity; AMH, AFC, and age had the highest predictive accuracy (ROCAUC 0.87, 0.80, and 0.82, respectively). After adjusting for age, only AMH and inhibin B were significantly associated with cycle irregularity. Inclusion of inhibin B and age to AMH in a multivariable model improved the predictive accuracy (ROCAUC 0.92). CONCLUSIONS: The novel marker AMH is a promising predictor for the occurrence of menopausal transition within 4 years. Adding inhibin B improved the prediction. Therefore, AMH alone or in combination with inhibin B may well prove a useful indicator for the reproductive status of an individual woman.

Antral follicle counts are related to age at natural fertility loss and age at menopause.

OBJECTIVE: The variability in ultrasound-based antral follicle counts sized 2-10 mm after allowing for age-related decline is considerable. This may represent differences in actual reproductive age among women. This hypothesis was tested by cohort comparison for distribution of age at occurrence of reproductive events. DESIGN: A model with a nonlinear mean decline with age was fitted to antral follicle counts (AFC) obtained in 163 regularly cycling fertile volunteers. Ages at last child birth and menopause were predicted from the individual AFC by using thresholds to represent these events and the model for decline with age. Distributions of the observed ages at last childbirth (proxy variable for loss of natural fertility) and ages at menopause were obtained from the BALSAC demographic database and the Prospect-EPIC study, respectively. The observed distributions were compared with the predicted distributions by using visual comparison and quantile-quantile plots. Predictions of age at last child and age at menopause were done using percentiles of the modeled AFC distribution for given age, and corresponding percentiles of the predicted distributions of age at these reproductive events, with predictions following from the position of a woman's AFC relative to these percentiles. RESULTS: The predicted distributions of age at last child and age at menopause showed good agreement with the observed distributions in the BALSAC and EPIC cohort. Compared with age alone, antral follicle counts gave some additional information for individual prediction of age at last child and menopause. CONCLUSIONS: The link between declining antral follicle counts and reproductively significant events like loss of natural fertility and menopause is strengthened by the high degree of similarity among the predicted and observed age distributions. Predictive usefulness of this relationship in a clinical setting may be more marginal, except in the case of women who have low AFCs for their age.