8 results on '"Yates, Allen P."'
Search Results
2. Modification of the Beckman-Coulter second-generation enzyme-linked immunosorbent assay protocol improves the reliability of serum antimüllerian hormone measurement.
- Author
-
Craciunas L, Roberts SA, Yates AP, Smith A, Fitzgerald C, and Pemberton PW
- Subjects
- Adult, Animals, Biomarkers blood, Cattle, Cohort Studies, Female, Humans, Middle Aged, Reproducibility of Results, Young Adult, Anti-Mullerian Hormone blood, Enzyme-Linked Immunosorbent Assay methods, Enzyme-Linked Immunosorbent Assay standards
- Abstract
Objective: To determine whether the modified Beckman-Coulter 2nd-generation (Gen II) antimüllerian hormone (AMH) assay (Gen IIm) provides more consistent results following storage at room temperature and on dilution than the original Gen II assay, to compare AMH results from the modified assay with those obtained from the original assay, and to assess the relationship between new AMH values and the antral follicle count (AFC)., Design: Cohort., Setting: Hospital fertility clinic., Patient(s): A total of 678 consecutive women (21-46 years old) investigated for subfertility., Intervention(s): None., Main Outcome Measure(s): AMH was measured by means of the Gen IIm assay protocol in women with known AFC. AMH values were obtained on a subset of serum samples by means of both original and modified assays., Result(s): Specimens analyzed by Gen IIm exhibited a proportional AMH response on dilution, and AMH values decreased by an average of 12.1% after 7 days at room temperature, in contrast to the steady increase seen with the use of the original Gen II assay. Gen IIm assay values were, on average, 51.4% higher than Gen II values. Population analysis suggested a conversion factor of 1.35 (95% CI 1.23-1.47) between the Gen IIm and historical data obtained for the Diagnostic Systems Laboratories AMH assay. The relationship between the Gen IIm AMH measurement and AFC was adequately represented by a linear function., Conclusion(s): The Gen IIm assay gave more reliable AMH results on sample dilution and storage than the original Gen II protocol. Findings obtained with the use of the original Gen II ELISA method should be treated with caution., (Copyright © 2015 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)
- Published
- 2015
- Full Text
- View/download PDF
3. The measurement of anti-Müllerian hormone: a critical appraisal.
- Author
-
Rustamov O, Smith A, Roberts SA, Yates AP, Fitzgerald C, Krishnan M, Nardo LG, and Pemberton PW
- Subjects
- Blood Preservation standards, Blood Specimen Collection standards, Enzyme-Linked Immunosorbent Assay statistics & numerical data, Humans, Immunoassay statistics & numerical data, Reproducibility of Results, Temperature, Anti-Mullerian Hormone blood
- Abstract
Context: Measurement of anti-Müllerian hormone (AMH) is perceived as reliable, but the literature reveals discrepancies in reported within-subject variability and between-method conversion factors. Recent studies suggest that AMH may be prone to preanalytical instability. We therefore examined the published evidence on the performance of current and historic AMH assays in terms of the assessment of sample stability, within-patient variability, and comparability of the assay methods., Evidence Acquisition: We reviewed studies (manuscripts or abstracts) measuring AMH, published in peer-reviewed journals between January 1, 1990, and August 1, 2013, using appropriate PubMed/Medline searches., Evidence Synthesis: AMH levels in specimens left at room temperature for varying periods increased by 20% in one study and by almost 60% in another, depending on duration and the AMH assay used. Even at -20°C, increased AMH concentrations were observed. An increase over expected values of 20-30% or 57%, respectively, was observed after 2-fold dilution in two linearity-of-dilution studies, but not in others. Several studies investigating within-cycle variability of AMH reported conflicting results, although most studies suggest that variability of AMH within the menstrual cycle appears to be small. However, between-sample variability without regard to menstrual cycle as well as within-sample variation appears to be higher using the GenII AMH assay than with previous assays, a fact now conceded by the kit manufacturer. Studies comparing first-generation AMH assays with each other and with the GenII assay reported widely varying differences., Conclusions: AMH may exhibit assay-specific preanalytical instability. Robust protocols for the development and validation of commercial AMH assays are required.
- Published
- 2014
- Full Text
- View/download PDF
4. Anti-Mullerian hormone: poor assay reproducibility in a large cohort of subjects suggests sample instability.
- Author
-
Rustamov O, Smith A, Roberts SA, Yates AP, Fitzgerald C, Krishnan M, Nardo LG, and Pemberton PW
- Subjects
- Adult, Blood Chemical Analysis methods, Cohort Studies, Female, Humans, Middle Aged, Ovary physiology, Regression Analysis, Reproducibility of Results, Retrospective Studies, Anti-Mullerian Hormone blood
- Abstract
Study Question: What is the variability of anti-Müllerian hormone (AMH) concentration in repeat samples from the same individual when using the Gen II assay and how do values compare to Gen I [Diagnostic Systems Ltd (DSL)] assay results?, Summary Answer: The Gen II AMH assay displayed appreciable variability, which can be explained by sample instability., What Is Known Already: AMH is the primary predictor of ovarian performance and is used to tailor gonadatrophin dosage in cycles of IVF/ICSI and in other routine clinical settings. Thus, a robust, reproducible and sensitive method for AMH analysis is of paramount importance. The Beckman Coulter Gen II ELISA for AMH was introduced to replace earlier DSL and Immunotech assays. The performance of the Gen II assay has not previously been studied in a clinical setting., Study Design, Size and Duration: We studied an unselected group of 5007 women referred for fertility problems between 1 September 2008 and 25 October 2011; AMH was measured initially using the DSL AMH ELISA and subsequently using the Gen II assay. AMH values in the two assays were compared using a regression model in log(AMH) with a quadratic adjustment for age. Additionally, women (n = 330) in whom AMH had been determined in different samples using both the DSL and Gen II assays (paired samples) identified and the difference in AMH levels between the DSL and Gen II assays was estimated using the age-adjusted regression analysis. A subset of 313 women had repeated AMH determinations (n = 646 samples) using the DSL assay and 87 women had repeated AMH determinations using the Gen II assay (n = 177 samples) were identified. A mixed effects model in log(AMH) was utilized to estimate the sample-to-sample (within-subject) coefficients of variation of AMH, adjusting for age. Laboratory experiments including sample stability at room temperature, linearity of dilution and storage conditions used anonymized samples., Main Results and the Role of Chance: In clinical practice, Gen II AMH values were ∼20% lower than those generated using the DSL assay instead of the 40% increase predicted by the kit manufacturer. Both assays displayed high within-subject variability (Gen II assay CV = 59%, DSL assay CV = 32%). In the laboratory, AMH levels in serum from 48 subjects incubated at RT for up to 7 days increased progressively in the majority of samples (58% increase overall). Pre-dilution of serum prior to assay, gave AMH levels up to twice that found in the corresponding neat sample. Pre-mixing of serum with assay buffer prior to addition to the microtitre plate gave higher readings (72% overall) compared with sequential addition. Storage at -20°C for 5 days increased AMH levels by 23% compared with fresh samples. The statistical significance of results was assessed where appropriate., Limitations, Reasons for Caution: The analysis of AMH levels is a retrospective study and therefore we cannot entirely rule out the existence of differences in referral practices or changes in the two populations., Wider Implications of the Findings: Our data suggests that AMH may not be stable under some storage or assay conditions and this may be more pronounced with the Gen II assay. The published conversion factors between the Gen II and DSL assays appear to be inappropriate for routine clinical practice. Further studies are urgently required to confirm our observations and to determine the cause of the apparent instability. In the meantime, caution should be exercised in the interpretation of AMH levels in the clinical setting., Conflict of Interest/study Funding: S. Roberts is supported by the NIHR Manchester Biomedical Research Centre.
- Published
- 2012
- Full Text
- View/download PDF
5. Anti-Müllerian hormone-tailored stimulation protocols improve outcomes whilst reducing adverse effects and costs of IVF.
- Author
-
Yates AP, Roberts SA, and Nardo LG
- Subjects
- Female, Humans, Pregnancy, Anti-Mullerian Hormone blood, Fertilization in Vitro methods, Ovulation Induction methods
- Published
- 2012
- Full Text
- View/download PDF
6. The reproducibility of serum anti-Müllerian hormone in subfertile women: within and between patient variability.
- Author
-
Rustamov O, Pemberton PW, Roberts SA, Smith A, Yates AP, Patchava SD, and Nardo LG
- Subjects
- Female, Follicle Stimulating Hormone blood, Humans, Infertility, Female therapy, Predictive Value of Tests, Reproducibility of Results, Anti-Mullerian Hormone blood, Biomarkers blood, Infertility, Female blood, Infertility, Female diagnosis, Ovulation Induction
- Abstract
Serum anti-Müllerian hormone concentrations vary significantly over time and this should be taken into account when tailoring treatment protocols for patients undergoing controlled ovarian hyperstimulation (COH). Compared with FSH, serum anti-Müllerian hormone may have greater discriminatory power because of its modest intrapatient variation and the larger interpatient variation., (Copyright © 2011 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)
- Published
- 2011
- Full Text
- View/download PDF
7. The relationships between AMH, androgens, insulin resistance and basal ovarian follicular status in non-obese subfertile women with and without polycystic ovary syndrome.
- Author
-
Nardo LG, Yates AP, Roberts SA, Pemberton P, and Laing I
- Subjects
- Adult, Age Factors, Body Mass Index, Female, Humans, Ovarian Follicle physiopathology, Polycystic Ovary Syndrome physiopathology, Prospective Studies, Androgens blood, Anti-Mullerian Hormone blood, Insulin Resistance, Ovarian Follicle growth & development, Polycystic Ovary Syndrome metabolism
- Abstract
Background: Hyperandrogenaemia and insulin resistance are prominent features of polycystic ovary syndrome (PCOS) and influence the process of folliculogenesis in women with the endocrinopathy. Anti-Müllerian hormone (AMH) levels are elevated in women with PCOS and studies including IVF subjects have shown that this is a reliable marker of ovarian performance. The aims of this prospective study were to assess the relationship between insulin resistance, androgens and AMH, and whether AMH contributes to altered folliculogenesis in non-obese women with PCOS., Methods: A total of 232 IVF candidates, 49 of whom had PCOS according to the Rotterdam 2003 consensus criteria, were recruited. AMH levels and ovarian morphology were assessed. The relationships between AMH and insulin resistance and androgenaemia in patients with and without PCOS were studied., Results: PCOS patients were slightly older than controls (median ages 34 and 30 years, respectively). AMH generally increased with antral follicle count (AFC), insulin, homeostatic model assessment of tissue insulin sensitivity (HOMA-IR), testosterone, free androgen index and luteinising hormone, and decreased with chronological age, homeostatic model assessment of steady state beta cell function (HOMA-B) and serum sex hormone binding globulin (SHBG). For these relationships there were no significant differences in the slopes between PCOS and non-PCOS patients. The ratio of AMH per antral follicle (AMH/AF) was higher in PCOS patients. Both PCOS and non-PCOS groups showed a very similar increase in AMH with increases in AFC, but the PCOS patients had consistently higher AMH across all AFC levels., Conclusions: These observations indicate that AMH is similarly related to insulin resistance and androgens in women with and without PCOS. This effect appears to be independent of age although an indirect causal effect due to ageing or some other mechanism cannot be ruled out. Excessive granulosa cell activity may be implicated in the abnormal follicular dynamic of the syndrome.
- Published
- 2009
- Full Text
- View/download PDF
8. Reply: reproducibility of AMH.
- Author
-
Rustamov, Oybek, Smith, Alexander, Roberts, Stephen A., Yates, Allen P., Fitzgerald, Cheryl, Krishnan, Monica, Nardo, Luciano G., and Pemberton, Philip W.
- Subjects
LETTERS ,ANTI-Mullerian hormone ,HUMAN reproduction ,BIOLOGICAL assay ,COMPARATIVE studies ,PROTEASE inhibitors - Published
- 2012
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.