PubMed Health⌕ Search

Biomedical subjects

John A Collins

Publications and source records attributed to John A Collins.

18 recordsLinked to original sources
PubMed2006

Value of ovarian reserve testing before IVF: a clinical decision analysis.

BACKGROUND: To assess the value of testing for ovarian reserve prior to a first cycle IVF incorporating patient and doctor valuation of mismatches between test results and treatment outcome. METHODS: A decision model was developed for couples who were considering participation in an IVF programme. Three strategies were evaluated: (I) withholding IVF without prior testing, (II) testing for ovarian reserve, and then deciding on IVF treatment if ovarian reserve was estimated to be sufficient, and (III) treatment with IVF without prior ovarian reserve testing. The outcome considered was the birth of a child. The valuation of the combination of the strategy conducted and the outcome accomplished was expressed on a distress scale in units of 'IVF cycles that were performed in vain'. Correct treatment with IVF and correct withholding of IVF were considered to bring no distress. The distress of withholding IVF in case pregnancy occurred is consequently specified by the ratio of the expected distress after incorrect withholding IVF to the expected distress after incorrect performing IVF (distress ratio). We interviewed both patients and doctors to determine realistic estimates for this distress ratio. RESULTS: The value of testing for ovarian reserve depends strongly on the expected pregnancy rate after IVF as well as on the valuation of the incorrect decisions from testing. For realistic ranges of the success rate after IVF and for distress ranges as were measured, treatment of all couples without testing was found to generate less distress than testing for ovarian reserve. The sensitivity and specificity of testing for ovarian reserve has to improve to 50 and 96% respectively, to make testing a valuable strategy. CONCLUSION: Based on the decision analysis, where current test accuracy and preference inventory among patients and physicians were used, testing for ovarian reserve seems not useful for current IVF programmes.

Attitude↗
PubMed2005

Breast cancer risk with postmenopausal hormonal treatment.

This review was designed to determine from the best evidence whether there is an association between postmenopausal hormonal treatment and breast cancer risk. Also, if there is an association, does it vary according to duration and cessation of use, type of regimen, type of hormonal product or route of administration; whether there is a differential effect on risk of lobular and ductal cancer; and whether hormone treatment is associated with breast cancers that have better prognostic factors? Data sources for the review included Medline, the Cochrane Database of Systematic Reviews (Cochrane Library, 2005) and reference lists in the identified citations. Eligible citations addressed invasive breast cancer risk among postmenopausal women and involved use of the estrogen products with or without progestin that are used as treatment for menopausal symptoms. Abstracted data were demographic groupings, categories of hormone use, categories of breast cancer, two-by-two tables of exposure and outcome and adjusted odds ratios, relative risks (RRs) or hazard rates. Average estimates of risk were weighted by the inverse variance method, or if heterogeneous, using a random effects model. The average risk of invasive breast cancer with estrogen use was 0.79 [95% confidence interval (95% CI) = 0.61-1.02] in four randomized trials involving 12 643 women. The average breast cancer risk with estrogen-progestin use was 1.24 (95% CI = 1.03-1.50) in four randomized trials involving 19 756 women. The average risks reported in recent epidemiological studies were higher: 1.18 (95% CI = 1.01-1.38) with current use of estrogen alone and 1.70 (95% CI = 1.36-2.17) with current use of estrogen-progestin. The association of breast cancer with current use was stronger than the association with ever use, which includes past use. For past use, the increased breast cancer risk diminished soon after discontinuing hormones and normalized within 5 years. Reasonably adequate data do not show that breast cancer risk varies significantly with different types of estrogen or progestin preparations, lower dosages or different routes of administration, although there is a small difference between sequential and continuous progestin regimens. Epidemiological studies indicate that estrogen-progestin use increases risk of lobular more than ductal breast cancer, but the number of studies and cases of lobular cancer remains limited. Among important prognostic factors, the stage and grade in breast cancers associated with hormone use [corrected] do not differ significantly from those in non-users, but breast cancers in estrogen-progestin users are significantly more likely to be estrogen receptor (ER) positive. In conclusion, valid evidence from randomized controlled trials (RCTs) indicates that breast cancer risk is increased with estrogen-progestin use more than with estrogen alone. Epidemiological evidence involving more than 1.5 million women agrees broadly with the trial findings. Although new studies are unlikely to alter the key findings about overall breast cancer risk, research is needed, however, to determine the role of progestin, evaluate the risk of lobular cancer and delineate effects of hormone use on receptor presence, prognosis and mortality in breast cancer.

Breast Neoplasms↗
PubMed2004

Spreading-rate dependence of melt extraction at mid-ocean ridges from mantle seismic refraction data.

A variety of observations indicate that mid-ocean ridges produce less crust at spreading rates below 20 mm yr(-1) (refs 1-3), reflecting changes in fundamental ridge processes with decreasing spreading rate. The nature of these changes, however, remains uncertain, with end-member explanations being decreasing shallow melting or incomplete melt extraction, each due to the influence of a thicker thermal lid. Here we present results of a seismic refraction experiment designed to study mid-ocean ridge processes by imaging residual mantle structure. Our results reveal an abrupt lateral change in bulk mantle seismic properties associated with a change from slow to ultraslow palaeo-spreading rate. Changes in mantle velocity gradient, basement topography and crustal thickness all correlate with this spreading-rate change. These observations can be explained by variations in melt extraction at the ridge, with a gabbroic phase preferentially retained in the mantle at slower spreading rates. The estimated volume of retained melt balances the approximately 1.5-km difference in crustal thickness, suggesting that changes in spreading rate affect melt-extraction processes rather than total melting.

Journal Article↗
PubMed2004

Overall prognosis with current treatment of infertility.

Few reports provide pregnancy or birth rates for large groups of infertile couples having a comprehensive range of treatments. This model utilizes published evidence about diagnosis, treatment, the duration of treatment and the proportion of couples receiving treatment. Assisted reproduction technology treatment (ART) utilization was set arbitrarily at three levels: 3, 10 or 50% of the couples that had no live birth after conventional treatment. For each diagnosis and treatment the model estimated total live births, singleton live births and multiple live births per 10,000 couples. The overall live birth rate with non-ART treatment would be 37%, involving 3,725 live births, of which 3,478 (93%) would be singleton and 247 (7%) would be multiple. With ART utilization at 3, 10 and 50% of couples with persistent infertility in each diagnostic category, live birth rates were 39, 43 and 47% respectively, with 8, 10 and 12% multiple births. The corresponding utilization of ART would be 244, 813 and 1481 ART cycles per 10(6) population per annum. Typical management of infertility would fall short of 50% live births even with extensive utilization of ART. Underlying unknown untreatable factors remain barriers to greater overall success in the treatment of infertility.

Birth Rate↗
PubMed2004

Comparison of basal follicle-stimulating hormone versus the clomiphene citrate challenge test for ovarian reserve screening.

OBJECTIVE: To compare the value of basal follicle-stimulating hormone (FSH) measurement vs. the clomiphene citrate challenge test (CCCT) in predicting the ability to achieve a pregnancy in women who are undergoing infertility treatment. DESIGN: Meta-analysis. SETTING: All studies that evaluated either basal FSH or the CCCT for determining the likelihood of pregnancy. PATIENT(S): Infertility population undergoing treatment, which was defined as patients undergoing ovulation induction, IUI, or in vitro fertilization (IVF). INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Diagnostic test characteristics were calculated and pooled using standard methods. Inability to achieve a pregnancy with treatment was considered as the "disease." RESULT(S): Twelve studies on basal FSH (with 6296 patients, mean age 33.8) and seven studies on the CCCT (with 1352 patients, mean age 34.5) fit our criteria and were analyzed. For basal FSH and the CCCT, the sensitivities were 6.6% (95% confidence interval [CI] 5.9, 7.3%) and 25.9% (95% CI 23.0, 29.0%), respectively, and specificities were 99.6% (95% CI 99.1, 99.9%) and 98.1% (95% CI 96.5, 99.1%), respectively. For "disease" prevalence ranging from 40%-100%, for basal FSH and the CCCT, the positive predictive values ranged from 91.7%-100% and 90.1%-100%, respectively, and negative predictive values ranged from 61.5%-0.0% and 66.5%-0.0%, respectively. CONCLUSION(S): Basal FSH and the CCCT are similar in predicting the ability to achieve a clinical pregnancy in women undergoing infertility treatment. With either test, a normal result is not useful, but an abnormal result virtually confirms that pregnancy will not occur with treatment.

Clomiphene↗
PubMed2003

Assessment of efficacy of varicocele repair for male subfertility: a systematic review.

BACKGROUND: Varicocele repair is a widely used treatment for subfertility. Our aim was to identify and combine the results from randomised controlled trials published to ascertain whether the pregnancy rates after varicocele repair are higher than those with no treatment. METHODS: We did a systematic review of seven studies identified by searching Medline and a register of controlled trials. We also searched the contents of specialist journals and the annual meeting programmes of relevant societies by hand. Inclusion criteria were treatment of varicocele in subfertile couples, random allocation to treatment and control groups, and pregnancy or livebirth rates as an outcome measure. We pooled data by use of fixed and random effects models. FINDINGS: None of seven eligible studies published between 1979 and 2002 described a strategy for concealment of the allocation sequence. There were 61 pregnancies among 281 treated couples and 50 pregnancies among 259 controls. The overall relative benefit of treatment was 1.01 (95% CI 0.73-1.40) by the fixed effects model and 1.04 (0.62-1.75) by the random effects model. The overall risk difference was 0.2% (-7 to 7) and 3% (-7 to 14), respectively. In subgroup analyses, varicocele treatment was not effective in trials restricted to male subfertility with clinical varicocele, or in those that included men with subclinical varicocele or normal semen analysis. However, this systematic review, done with a meta-analytical method, might have had insufficient power to detect small effects because of the small number of patients in some subgroups. INTERPRETATION: Varicocele repair does not seem to be an effective treatment for male or unexplained subfertility.

Female↗
PubMed2003

How does the WHI study alter the risk-benefit ratio of HT?

Good clinical practice depends on knowledge of the current best medical care research evidence, but clinicians must be able to determine what is the best evidence and whether this evidence is relevant to their own patients. At the heart of evidence-based medicine is the assessment of the validity, importance, and relevance of a given study. These may be evaluated by asking key questions; here these questions are applied to the WHI study.

Estrogen Replacement Therapy↗
PubMed2003

Evidence-based medicine for treatment: an in vitro fertilization trial.

Evidence-based evaluation of treatment is a pivotal component of an effective and satisfying clinical practice. When the best evidence has been identified, it can be efficiently assessed on three levels: Are the methods valid? Is the effect sufficiently large to be meaningful to patients? Are the patients, intervention(s), and outcomes studied applicable to our own patients? These criteria were applied to a multicenter trial that evaluated whether intracytoplasmic sperm injection (ICSI) was superior to in vitro fertilization (IVF) among infertile couples with no known male factor who were on a waiting list for IVF. The study was a well-designed randomized controlled trial that effectively concealed the randomization list and took reasonable steps to exclude bias. The results seemed important because the number needed to treat (13) was relatively low and significant, but the primary outcome (implantation rate) was not clinically meaningful. The trial results would have been relevant to most infertile couples with no known male factor if it had been powered to evaluate a difference in a more relevant clinical outcome, such as live birth. Thus, it has not been shown definitively that ICSI is inferior to IVF among couples with no known male factor, and clinical demand for ICSI may continue to rise.

Clinical Trials as Topic↗
PubMed2003

Evaluating systematic reviews and meta-analyses.

Systematic review and meta-analysis procedures make use of explicit methods to methodically search and critically appraise and synthesize the medical care research literature. The methods involve refining a clinical question, designing a search procedure to find eligible studies, and determining the validity of the eligible studies. Independent data extraction by two or more reviewers is preferred. Agreement between the reviewers with respect to relevance and validity should be measured. Meta-analysis procedures estimate an overall average effect from the individual study effects and determine whether these effects appear to measure the same relationship (that is, the studies are not heterogeneous). In the inverse variance method, which is most frequently applied, the overall effect is a weighted average of the individual study effects, where each weight is the inverse of the study variance. To evaluate a systematic review, first determine whether it addresses a question that is relevant to the patients, treatments, and outcomes that are usual in your clinical practice. Then assess the validity of the systematic review, which is reflected by quality of the individual studies, the rigor with which the systematic methods were applied, and the extent of heterogeneity. If the results of the systematic review are valid, then is the effect important enough to make a difference in your clinical practice? Applying the results to an individual patient involves the absolute treatment effect or the number needed to treat, and an awareness of the patient's specific level of risk and personal preferences.

Data Interpretation, Statistical↗
PubMed2002

Validation of a model predicting spontaneous pregnancy among subfertile untreated couples.

OBJECTIVE: To provide external validation of the Eimers model, which predicts spontaneous pregnancy among subfertile couples within the first year after the definitive establishment of the diagnostic category. DESIGN: Live birth rates predicted by an adapted version of the Eimers model were tested against observed live birth rates in a Canadian cohort study. SETTING: Fertility clinics in university medical centers. PATIENT(S): One thousand sixty-one couples consulting for subfertility due to cervical hostility, male subfertility, or unexplained subfertility. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): We measured the discriminative ability and reliability of the predictions from the model. RESULT(S): The live birth rate was lower in the Canadian population than in the Eimers population. Overall, the prognostic effect of the predictors did not differ significantly in both populations. The model showed moderate predictive power in the Canadian population. With adjustment of the average live birth rate, the reliability of the model was satisfactory. CONCLUSION(S): The Eimers model gave reliable spontaneous pregnancy predictions in the Canadian validation population after adjustment of the average live birth rate.

Adult↗
PubMed2002

Perimenopausal use of reproductive hormones effects on breast and endometrial cancer.

The effect of reproductive hormone use in the form of oral contraception or HRT on endometrial cancer incidence is not caused by simply bias: the epidemiologic studies are consistent; the effect of ERT is large; the biologic rationale cited is a plausible mechanism; and the response to progestin in oral contraception or combined HRT tends to confirm the biologic mechanism. In contrast, it remains unclear whether changes in breast cancer incidence following use of oral contraception and HRT are caused by hormone exposure or to other factors: the results of epidemiologic studies are not entirely consistent, and the smaller relative effect on risk of breast cancer is susceptible to bias and other sources of error. Although the exact nature of the association between repro ductive hormone use and breast cancer incidence is not yet clear, breast cancer is a common neoplasm in older women. Prescribers and users should take this into account in weighing benefits to ensure that unnecessary risks are avoided.

Breast Neoplasms↗
PubMed2002

The SOGC statement on the WHI report on estrogen and progestin use in postmenopausal women.

The recent Women's Health Initiative study report evaluated the long-term benefits and risks of hormone replacement therapy among healthy postmenopausal women. The report showed that the risk-benefit profile of continuous combined hormone replacement therapy was not consistent with the primary prevention of coronary heart disease. The Women's Health Initiative study of continuous combined hormone replacement therapy is a landmark study and the results provide valuable information for patients and clinicians. However, the most common indication for hormone replacement therapy is menopausal symptoms, for which it is effective, not prevention of disease, and the most common use is for less than three years. Nevertheless, even short-term use has small effects on some outcomes. This statement discusses how the findings of the Women's Health Initiative study can be applied to reach appropriate clinical decisions.

Aged↗
PubMedDate not supplied

Alternative approaches in IVF.

Various new developments in clinical and basic science which may impact on IVF in the near or distant future will be discussed in this review. These key areas include the regulation of early follicle development and the extended in-vitro culture of oocytes and embryos. Moreover, alternative compounds and ovarian stimulation protocols will be discussed, along with highlights in the development of the cryopreservation of excess oocytes or embryos. Finally, the health economics of IVF is addressed.

Cells, Cultured↗