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Dive into the research topics where M.J. Eijkemans is active.

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Featured researches published by M.J. Eijkemans.


European Journal of Endocrinology | 2011

Assessment of androgen concentration in women: liquid chromatography–tandem mass spectrometry and extraction RIA show comparable results

Femi Janse; M.J. Eijkemans; Angelique J. Goverde; Eef Lentjes; Annemieke Hoek; C.B. Lambalk; Theresa E. Hickey; Bart C.J.M. Fauser; Robert J. Norman

OBJECTIVE The measurement of serum testosterone in women is challenging due to lack of trueness, precision, and sensitivity of various available testosterone assays. Accurate assessment of testosterone in women is crucial especially in conditions associated with alleged over- or under-production of testosterone, such as in polycystic ovary syndrome (PCOS) or primary ovarian insufficiency (POI). The aim of this study was to measure and compare androgen concentrations in women with PCOS, POI, and female controls and to evaluate the performance of extraction RIA and liquid chromatography-tandem mass spectrometry (LC-MS/MS) in these women. DESIGN Cross-sectional study. METHODS Carefully phenotyped women with POI (n=208) or PCOS (n=200) and 45 healthy, regularly cyclic female controls were included. Method comparison analyses were performed for total testosterone, androstenedione (AD), and DHEA, as measured by LC-MS/MS and extraction RIA. RESULTS All androgen levels were significantly elevated in women with PCOS compared with POI patients (P<0.05) and controls (P<0.05). Women with POI presented with similar androgen concentrations as controls, except for AD. Compared with measurements by extraction RIA, testosterone, DHEA, and AD concentrations measured by LC-MS/MS were systematically lower. However, using extraction RIA and LC-MS/MS, testosterone, DHEA, and AD measurements were shown to have good agreement as assessed by Bland-Altman analysis and intraclass correlation coefficient: 0.95 (95% confidence interval 0.94-0.91), 0.83 (0.79-0.86), and 0.96 (0.95-0.97) respectively. CONCLUSIONS LC-MS/MS, compared with a labor-intensive extraction RIA, shows good precision, sensitivity, and high accuracy for measuring female testosterone, DHEA, and AD concentrations under various clinical conditions. LC-MS/MS, therefore, represents a convenient and reliable assay for both clinical and research purposes, where androgen measurement in women is required.


BMJ | 2015

Prevention of multiple pregnancies in couples with unexplained or mild male subfertility: randomised controlled trial of in vitro fertilisation with single embryo transfer or in vitro fertilisation in modified natural cycle compared with intrauterine insemination with controlled ovarian hyperstimulation

A.J. Bensdorp; R. I. Tjon-Kon-Fat; P. M. M. Bossuyt; C.A.M. Koks; G.J.E. Oosterhuis; Annemieke Hoek; Peter G.A. Hompes; F. J. Broekmans; Harold R. Verhoeve; J.P. de Bruin; R. van Golde; Sjoerd Repping; B.J. Cohlen; M. D. A. Lambers; van Peter Bommel; Denise A. M. Perquin; J.M.J. Smeenk; M. J. Pelinck; Judith Gianotten; Diederik A. Hoozemans; J. W. M. Maas; M.J. Eijkemans; F. van der Veen; B.W. Mol; M. van Wely

Objectives To compare the effectiveness of in vitro fertilisation with single embryo transfer or in vitro fertilisation in a modified natural cycle with that of intrauterine insemination with controlled ovarian hyperstimulation in terms of a healthy child. Design Multicentre, open label, three arm, parallel group, randomised controlled non-inferiority trial. Setting 17 centres in the Netherlands. Participants Couples seeking fertility treatment after at least 12 months of unprotected intercourse, with the female partner aged between 18 and 38 years, an unfavourable prognosis for natural conception, and a diagnosis of unexplained or mild male subfertility. Interventions Three cycles of in vitro fertilisation with single embryo transfer (plus subsequent cryocycles), six cycles of in vitro fertilisation in a modified natural cycle, or six cycles of intrauterine insemination with ovarian hyperstimulation within 12 months after randomisation. Main outcome measures The primary outcome was birth of a healthy child resulting from a singleton pregnancy conceived within 12 months after randomisation. Secondary outcomes were live birth, clinical pregnancy, ongoing pregnancy, multiple pregnancy, time to pregnancy, complications of pregnancy, and neonatal morbidity and mortality Results 602 couples were randomly assigned between January 2009 and February 2012; 201 were allocated to in vitro fertilisation with single embryo transfer, 194 to in vitro fertilisation in a modified natural cycle, and 207 to intrauterine insemination with controlled ovarian hyperstimulation. Birth of a healthy child occurred in 104 (52%) couples in the in vitro fertilisation with single embryo transfer group, 83 (43%) in the in vitro fertilisation in a modified natural cycle group, and 97 (47%) in the intrauterine insemination with controlled ovarian hyperstimulation group. This corresponds to a risk, relative to intrauterine insemination with ovarian hyperstimulation, of 1.10 (95% confidence interval 0.91 to 1.34) for in vitro fertilisation with single embryo transfer and 0.91 (0.73 to 1.14) for in vitro fertilisation in a modified natural cycle. These 95% confidence intervals do not extend below the predefined threshold of 0.69 for inferiority. Multiple pregnancy rates per ongoing pregnancy were 6% (7/121) after in vitro fertilisation with single embryo transfer, 5% (5/102) after in vitro fertilisation in a modified natural cycle, and 7% (8/119) after intrauterine insemination with ovarian hyperstimulation (one sided P=0.52 for in vitro fertilisation with single embryo transfer compared with intrauterine insemination with ovarian hyperstimulation; one sided P=0.33 for in vitro fertilisation in a modified natural cycle compared with intrauterine insemination with controlled ovarian hyperstimulation). Conclusions In vitro fertilisation with single embryo transfer and in vitro fertilisation in a modified natural cycle were non-inferior to intrauterine insemination with controlled ovarian hyperstimulation in terms of the birth of a healthy child and showed comparable, low multiple pregnancy rates. Trial registration Current Controlled Trials ISRCTN52843371; Nederlands Trial Register NTR939.


Trials | 2015

High frequency oscillations in the intra-operative ECoG to guide epilepsy surgery ("The HFO Trial") : study protocol for a randomized controlled trial

Maryse A. van ’t Klooster; Frans S. S. Leijten; Geertjan Huiskamp; Hanneke E. Ronner; Johannes C. Baayen; Peter C. van Rijen; M.J. Eijkemans; Kees P. J. Braun; Maeike Zijlmans

BackgroundIntra-operative electrocorticography, based on interictal spikes and spike patterns, is performed to optimize delineation of the epileptogenic tissue during epilepsy surgery. High frequency oscillations (HFOs, 80–500 Hz) have been identified as more precise biomarkers for epileptogenic tissue. The aim of the trial is to determine prospectively if ioECoG-tailored surgery using HFOs, instead of interictal spikes, is feasible and will lead to an equal or better seizure outcome.Methods\DesignWe present a single-blinded multi-center randomized controlled trial “The HFO Trial” including patients with refractory focal epilepsy of all ages who undergo surgery with intra-operative electrocorticography. Surgery is tailored by HFOs (arm 1) or interictal spikes (arm 2) in the intra-operative electrocorticography. Primary outcome is post-operative outcome after 1 year, dichotomized in seizure freedom (Engel 1A and 1B) versus seizure recurrence (Engel 1C-4). Secondary outcome measures are the volume of resected tissue, neurologic deficits, surgical duration and complications, cognition and quality of life. The trial has a non-inferiority design to test feasibility and at least equal performance in terms of surgical outcome. We aim to include 78 patients within 3 years including 1 year follow-up. Results are expected in 2018.DiscussionThis trial provides a transition from observational research towards clinical interventions using HFOs. We address methodological difficulties in designing this trial. We expect that the use of HFOs as a biomarker for tailoring will increase the success rate of epilepsy surgery while reducing resection volume. This may reduce neurological deficits and yield a better quality of life. Future technical developments, such as validated automatic online HFO identification, could, together with the attained clinical knowledge, lead to a new objective tailoring approach in epilepsy surgery.Trial registrationThis trial is registered at the US National Institutes of Health (ClinicalTrials.gov) #NCT02207673 (31 July 2014) and the Central Committee on Research Involving Human Subjects, The Netherlands #NL44257.041.13 (18 March 2014).


Human Reproduction | 2018

Natural conception rates in couples with unexplained or mild male subfertility scheduled for fertility treatment: a secondary analysis of a randomized controlled trial

R van Eekelen; R. I. Tjon-Kon-Fat; P. M. M. Bossuyt; N van Geloven; M.J. Eijkemans; A.J. Bensdorp; F. van der Veen; Ben W. Mol; M. van Wely

STUDY QUESTION What is the natural conception rate over the course of 12 months in couples with unexplained or mild male subfertility who are scheduled for fertility treatment and have a predicted unfavourable prognosis for natural conception? SUMMARY ANSWER The natural conception rate over the course of 12 months in couples who were allocated to treatment was estimated to be 24.5% (95% CI: 20-29%). WHAT IS KNOWN ALREADY After starting treatment, couples often perceive unsuccessful cycles as evidence of definitive failure even though they are still able to conceive naturally in between and after treatment. The magnitude of the natural conception rate for couples who chose to commence treatment is unknown, as is whether the calculated prognosis before commencing treatment is still applicable. STUDY DESIGN, SIZE, DURATION We performed a secondary analysis of a randomized controlled trial including couples with unexplained or mild male subfertility and an unfavourable prognosis for natural conception. Couples were allocated to either three cycles IVF with single embryo transfer (SET), six cycles of IVF in a modified natural cycle (MNC) or six cycles of IUI with controlled ovarian hyperstimulation (IUI-COH). The detailed data collection in this trial allowed us to study the conception rates in periods that couples were not receiving treatment. PARTICIPANTS/MATERIALS, SETTINGS, METHODS We split the dataset into periods during which couples were treated and periods during which they were not treated. Couples could conceive naturally in the periods before, in between and after treatment cycles. The outcome was ongoing pregnancy, thus natural conception rate refers to natural conception leading to ongoing pregnancy. We performed a Cox proportional hazards analysis with female age, duration of subfertility and a time-varying covariate with four categories: IVF-SET, IVF-MNC, IUI-COH and no treatment. We used this Cox model to estimate the natural conception rate over 12 months of no treatment. MAIN RESULTS AND THE ROLE OF CHANCE Out of 602 included couples, there were 342 ongoing pregnancies, of which 77 (23%) resulted from natural conception. The estimated natural conception rate over 12 months was 24.5% (95% CI: 20-29%) on cohort level. Estimated rates for female age varying between 18 and 38 years and duration of subfertility between 1 and 3 years ranged from 22 to 35%. LIMITATIONS, REASONS FOR CAUTION We considered couples at risk for natural conception when not receiving treatment, whereas they might not have had periovulatory sexual intercourse. As couples were scheduled for treatment, it is possible that these couples were less inclined to try to conceive naturally, potentially leading to an underestimation of their natural conception rate if they kept trying to conceive. WIDER IMPLICATIONS OF THE FINDINGS Couples with unexplained subfertility who are about to start fertility treatment, still have about a one in four chance of ongoing pregnancy due to natural conception over 12 months. This information can add to the counselling of couples who commenced fertility treatment after failed cycles and to emphasize not to cease their natural attempts. STUDY FUNDING/COMPETING INTEREST(S) The INeS trial was supported by a grant from ZonMW, the Dutch Organization for Health Research and Development (120620027), and a grant from Zorgverzekeraars Nederland, the Dutch association of health care insurers (09-003). The funders had no role in study design, collection, analysis and interpretation of the data. B.W.M. is supported by a NHMRC Practitioner Fellowship (GNT1082548). B.W.M. reports consultancy for ObsEva, Merck and Guerbet. No other potential conflicts of interest reported. TRIAL REGISTRATION NUMBER The INeS trial was registered at the Dutch trial registry (NTR 939).


Human Reproduction | 2018

External validation of a dynamic prediction model for repeated predictions of natural conception over time

R van Eekelen; David J. McLernon; M. van Wely; M.J. Eijkemans; Sohinee Bhattacharya; F. van der Veen; N van Geloven

STUDY QUESTION How well does a previously developed dynamic prediction model perform in an external, geographical validation in terms of predicting the chances of natural conception at various points in time? SUMMARY ANSWER The dynamic prediction model performs well in an external validation on a Scottish cohort. WHAT IS KNOWN ALREADY Prediction models provide information that can aid evidence-based management of unexplained subfertile couples. We developed a dynamic prediction model for natural conception (van Eekelen model) that is able to update predictions of natural conception when couples return to their clinician after a period of unsuccessful expectant management. It is not known how well this model performs in an external population. STUDY DESIGN, SIZE, DURATION A record-linked registry study including the long-term follow-up of all couples who were considered unexplained subfertile following a fertility workup at a Scottish fertility clinic between 1998 and 2011. Couples with anovulation, uni/bilateral tubal occlusion, mild/severe endometriosis or impaired semen quality according to World Health Organization criteria were excluded. PARTICIPANTS/MATERIALS, SETTING, METHODS The endpoint was time to natural conception, leading to an ongoing pregnancy (defined as reaching a gestational age of at least 12 weeks). Follow-up was censored at the start of treatment, at the change of partner or at the end of study (31 March 2012). The performance of the van Eekelen model was evaluated in terms of calibration and discrimination at various points in time. Additionally, we assessed the clinical utility of the model in terms of the range of the calculated predictions. MAIN RESULTS AND THE ROLE OF CHANCE Of a total of 1203 couples with a median follow-up of 1 year and 3 months after the fertility workup, 398 (33%) couples conceived naturally leading to an ongoing pregnancy. Using the dynamic prediction model, the mean probability of natural conception over the course of the first year after the fertility workup was estimated at 25% (observed: 23%). After 0.5, 1 and 1.5 years of expectant management after the completion of the fertility workup, the average probability of conceiving naturally over the next year was estimated at 18% (observed: 15%), 14% (observed: 14%) and 12% (observed: 12%). Calibration plots showed good agreement between predicted chances and the observed fraction of ongoing pregnancy within risk groups. Discrimination was moderate with c statistics similar to those in the internal validation, ranging from 0.60 to 0.64. The range of predicted chances was sufficiently wide to distinguish between couples having a good and poor prognosis with a minimum of zero at all times and a maximum of 55% over the first year after the workup, which decreased to maxima of 43% after 0.5 years, 34% after 1 year and 29% after 1.5 years after the fertility workup. LIMITATIONS, REASONS FOR CAUTION The model slightly overestimated the chances of conception by ~2-3% points on group level in the first-year post-fertility workup and after 0.5 years of expectant management, respectively. This is likely attributable to the fact that the exact dates of completion of the fertility workup for couples were missing and had to be estimated. WIDER IMPLICATIONS OF THE FINDINGS The van Eekelen model is a valid and robust tool that is ready to use in clinical practice to counsel couples with unexplained subfertility on their individualized chances of natural conception at various points in time, notably when couples return to the clinic after a period of unsuccessful expectant management. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by a Chief Scientist Office postdoctoral training fellowship in health services research and health of the public research (ref PDF/12/06). There are no conflicts of interest.


Human Reproduction | 2015

Is IVF—served two different ways—more cost-effective than IUI with controlled ovarian hyperstimulation?

R.I. Tjon-Kon-Fat; A.J. Bensdorp; P.M.M. Bossuyt; C.A.M. Koks; G.J.E. Oosterhuis; Annemieke Hoek; Peter G.A. Hompes; F. J. Broekmans; Harold R. Verhoeve; J.P. de Bruin; R. van Golde; Sjoerd Repping; B.J. Cohlen; M. D. A. Lambers; P.F. van Bommel; Denise A. M. Perquin; J.M.J. Smeenk; M. J. Pelinck; Judith Gianotten; Diederik A. Hoozemans; J. W. M. Maas; Henk Groen; M.J. Eijkemans; F. van der Veen; B.W.J. Mol; M. van Wely


Fertility and Sterility | 2005

A Randomized Clinical Trial Assessing the Effectiveness Of Intrauterine Insemination For Couples With an Isolated Cervical Factor

P. Steures; J.W. van der Steeg; F. van der Veen; Peter G.A. Hompes; M.J. Eijkemans; B.W. Mol


Human Reproduction | 2017

IVF or IUI as first-line treatment in unexplained subfertility : the conundrum of treatment selection markers

R.I. Tjon-Kon-Fat; Parvin Tajik; Mohammad Hadi Zafarmand; A.J. Bensdorp; P.M.M. Bossuyt; G.J.E. Oosterhuis; R. van Golde; Sjoerd Repping; M. D. A. Lambers; Denise A. M. Perquin; M. J. Pelinck; Judith Gianotten; J. W. M. Maas; M.J. Eijkemans; F. van der Veen; B.W.J. Mol; M. van Wely


Human Reproduction | 2012

SESSION 60: PCOS AND AMH

Y.V. Louwers; M. Roest-Schalken; J. Roeters-van Lennep; Eric J.G. Sijbrands; J.S.E. Laven; J.P. de Bruin; S.C. Braam; M. Brandes; J.M.J. Smeenk; W.L.D.M. Nelen; B.W. Mol; C.J.C.M. Hamilton; Z. Yapici Coskun; G. Bozdag; B.O. Yildiz; I. Esinler; H. Yarali; Mette Petri Lauritsen; J.G. Bentzen; Anja Pinborg; Anne Loft; L.L. Thuesen; A. Nyboe Andersen; F. Yarde; M. Voorhuis; B.C.J.M. Fauser; M.J. Eijkemans; F.J. Broekmans; O. Rustamov; P.W. Pemberton


Human Reproduction | 2011

SELECTED ORAL COMMUNICATION SESSION, SESSION 33: AGONISTS AND ANTAGONISTS, Tuesday 5 July 2011 10:00 – 11:30

A. Watanabe; M. Jinno; J. Hirohama; N. Hatakeyama; R. Hiura; M. Sterrenburg; Christophe Blockeel; M.J. Eijkemans; S.L. Broer; Nick S. Macklon; F.J. Broekmans; Paul Devroey; Bart C.J.M. Fauser; R. Al-Karaki; R. Irzouqi; F. Khalifa; M. Taher; M. Sarraf; I. Cedrin – Durnerin; A. Guivarch; Jean-Noël Hugues; B. Bstandig; I. Parneix; C. Vasseur; S. Dubourdieu; A. Colombel; A. Marszalek; Vanessa Gayet; Valérie Blanchet; Isabelle Streuli

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B.W. Mol

University of Adelaide

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M. van Wely

University of Amsterdam

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P. Steures

University of Amsterdam

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Annemieke Hoek

University Medical Center Groningen

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