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At least 163 records · Page 9Linked to original sources
PubMed1998

Epidemiology of oral contraceptives and cardiovascular disease.

PURPOSE: To review the association between combined oral contraceptives and cardiovascular disease, with emphasis on oral contraceptives containing low doses of estrogen (low-dose oral contraceptives). DATA SOURCES: A systematic search of the MEDLINE database was done for all relevant articles published between 1967 (when low-dose oral contraceptives were introduced in the United States) and June 1997. Textbooks, meeting proceedings, and reference lists were also searched. STUDY SELECTION: All English-language human epidemiology studies of oral contraceptives that used cardiovascular disease as an end point were reviewed. Animal and metabolic studies were reviewed only if they were especially relevant to the mechanism of action of oral contraceptives. DATA EXTRACTION: Descriptive and analytic data from each study were collected. DATA SYNTHESIS: Data were organized by cardiovascular end point, study design, estrogen dose, and type of progestogen. Data on relative and absolute risk are presented to address current prescription guidelines. CONCLUSIONS: The risk for cardiovascular disease is lower with current preparations of oral contraceptives, including those that contain the new progestogens, than with older oral contraceptives containing high doses of estrogen. Among users of low-dose oral contraceptives, cardiovascular diseases occur mainly in smokers and women with predisposing factors. Every effort should be made to encourage smoking cessation among potential users of oral contraceptives.

Animals↗
PubMed1998

Infections acquired during cardiopulmonary resuscitation: estimating the risk and defining strategies for prevention.

PURPOSE: To estimate the risk for acquiring an infectious disease during cardiopulmonary resuscitation (CPR) or CPR training and to identify strategies to minimize that risk. DATA SOURCES: English-language articles published since 1965 were identified through a search of the MEDLINE database and selected bibliographies. STUDY SELECTION: Studies that contained information about transmission of infectious organisms, particularly HIV and other bloodborne viruses that might be transmitted through mouth-to-mouth ventilation, contact exposures, and needlesticks during CPR. DATA EXTRACTION: Descriptive and analytic data from each study. DATA SYNTHESIS: Fear of acquiring infection, especially HIV infection, can delay prompt initiation of mouth-to-mouth ventilation. Although pathogens can be isolated from the saliva of infected persons, salivary transmission of bloodborne viruses is unusual and transmission of infection has been rare: Only 15 documented cases have been reported. Most of these cases involved a bacterial pathogen, such as Neisseria meningitidis. Transmission of hepatitis B virus, hepatitis C virus, or cytomegalovirus during CPR has not been reported; all three reported cases of HIV infection acquired during resuscitation of an infected patient resulted from high-risk cutaneous exposures. There have been no reports of infection acquired during CPR training. Simple infection-control measures, including use of barrier devices, can reduce the risk for acquisition of an infectious disease during CPR and CPR training. Postexposure protocols can further protect potential rescuers and trainees. CONCLUSIONS: The benefit of initiating lifesaving resuscitation in a patient in cardiopulmonary arrest greatly outweighs the risk for secondary infection in the rescuer or the patient. Nevertheless, use of simple infection-control measures during CPR and CPR training can reduce a very low level of risk even further.

Bacterial Infections↗
PubMed1999

The evolving role of ambulatory arrhythmia monitoring in general clinical practice.

PURPOSE: To evaluate the efficacy of various ambulatory electrocardiographic monitors for the diagnosis of arrhythmia-related disorders and to provide recommendations for their use in clinical practice. DATA SOURCES: Studies published since 1988 were identified through search of the MEDLINE database. STUDY SELECTION: Studies that met methodologic criteria for minimal bias and had clinical relevance were selected. DATA EXTRACTION: Descriptive and analytic data from each study. DATA SYNTHESIS: Ambulatory electrocardiographic monitors, specifically transtelephonic continuous-loop event recorders, are highly effective for establishing a diagnosis in patients with palpitations but are less effective for establishing a diagnosis in patients with syncope. Clinicians may use these devices to monitor for nonsustained ventricular tachycardia in patients at potentially high risk for sudden arrhythmic death; however, few data are available to support this practice. Ambulatory monitors are useful for assessment of the safety and efficacy of antiarrhythmic medications and the recurrence of symptomatic supraventricular arrhythmias. New ambulatory arrhythmia monitoring devices are being developed that may facilitate outpatient management of chronic cardiac disease. CONCLUSIONS: Ambulatory electrocardiographic monitors, particularly transtelephonic continuous-loop event recorders, aid in the diagnosis of symptomatic arrhythmias. These devices are also useful for monitoring the effectiveness and safety of antiarrhythmic medications. Guidelines are lacking for use of these devices to assess prognosis in patients at potential risk for sudden arrhythmic death.

Algorithms↗
PubMed1988

Serum levels of carcinomedin (1-keto-24-methyl-25-hydroxycholecalciferol) as an indicator of the progression of cancer. Preliminary results of a prospective study.

The serum levels of the cholesterol derivative 1-keto-24-methyl-25-hydroxycholecalciferol found in patients with cancer varies after surgical, chemical or radiotherapy treatments. The serum level associated with the vitamin profile has a predictive value for evaluating progress of the disease and therapeutic efficacy. The detection, identification and assay of a vitamin D3 derivative, 1-keto-24-methyl-25-hydroxycholecalciferol, named carcinomedin by us, in the serum of cancer patients was described in prior work. Also, the assay of carcinomedin, combined with those of serum levels of vitamin A, beta-carotene and alpha-tocopherol indicated a statistically significant correlation between these parameters and the localization of the primary neoplastic mass. In spite of the probable connection between carcinomedin and the presence of a neoplastic mass, several questions remain unanswered. In particular, it may be asked if the stage and progression of the tumor, surgical, chemotherapeutic or radiotherapeutic treatments may be related with any type of change in the serum levels of carcinomedin and fat soluble vitamins? To verify and respond to these questions, patients with various cancers (stomach, esophagus, breast, ovaries, uterus, etc.) were followed for three years. Clinical data were compared to analytical data supplied by assays of carcinomedin and the fat soluble vitamins.

Adult↗
PubMed1982

The implications of early psychopathology for the analysability of narcissistic personality disorders.

This paper explores the influences of early psychopathology on questions of analysability in general and upon the analysability of narcissistic personality disorders in particular. Because various theoretical perspectives influence the meanings attributed to genetic and analytic data and may shape the emergence and unfolding of the data, current definitions of analytic process and analysability are reviewed. Work with two unanalysable narcissistic personality disorders is presented to facilitate an inquiry into the influence of their early psychopathology on their egos' limited capacity to become involved in an analytic process. This inquiry is pursued by exploring these subjects' character organizations, life histories and analytic and therapeutic experiences from four complementary perspectives: First, the relationship of their early life experiences to their ego development is examined with particular emphasis on the integration of their self-representations and the development of their capacity for fantasy, self-observation and creative sublimation. Second, the influence of process versus shock trauma in the genesis of their character pathology is delineated. Third, the development of trust in relationship to a variety of alliances with the analyst is considered in relationship to the assessment of analysability. Fourth, the question of their diagnosis is explored.

Adult↗
PubMed1996

Effectiveness of vaginal Papanicolaou smear screening after total hysterectomy for benign disease.

OBJECTIVE: Using literature review, we assessed (1) Papanicolaou smear screening recommendations after hysterectomy for benign disease, (2) total hysterectomy for benign disease as a risk for vaginal dysplasia or carcinoma, and (3) effectiveness of screening for vaginal carcinoma after total hysterectomy for benign disease. DATA SOURCES: We considered (1) organizations' recommendations about screening, (2) references from major textbooks of gynecology, and (3) MEDLINE searches of English-language studies published from 1966 through 1995 using the search strategy (hysterectomy and vaginal smears) or (vaginal smears and vaginal neoplasms). STUDY SELECTION: Published or verbal confirmations of screening recommendations were eligible. Criteria for assessing risk of vaginal dysplasia or carcinoma included original research, documented reports of hysterectomy as an exposure, and evidence of preinvasive vaginal disease or vaginal carcinoma outcomes. We sought data assessing burden of suffering, screening efficacy, and effectiveness of early detection. DATA EXTRACTION: Descriptive and analytic data from each study were abstracted. DATA SYNTHESIS: Screening recommendations were categorized by the organizations' positions: two opposed screening, two supported screening, and six lacked specific guidelines. Data on the risk between total hysterectomy for benign disease and subsequent vaginal carcinoma were organized by study design (three case control, two cohort, and 13 case series) and described. Data on screening effectiveness were organized to address the criteria advocated by the US Preventive Services Task Force. CONCLUSIONS: There are conflicting guidelines on screening after hysterectomy and conflicting data on the risk of vaginal carcinoma after total hysterectomy for benign disease, though the best-designed research suggests no association. There is insufficient evidence to recommend routine vaginal smear screening in women after total hysterectomy for benign disease.

Carcinoma in Situ↗
PubMed1992

Transferability of clinical laboratory data within a health care region.

Analytical data for S-Creatinine and S-Urate are presented from seventeen laboratories in the Swedish Uppsala-Orebro regional quality assessment program. The bias and imprecision as well as the instability of the measurement procedures in the participating laboratories were estimated over three 14-week periods. Bias was estimated by a linear least squares fit of the difference between measured and assigned values vs. assigned values, and expressed in absolute and relative terms. Instability of the measurement procedures was estimated by comparing slope and intercept of regression lines of measured vs. assigned values from three fourteen week periods. According to our experiences we recommend regression analysis to describe the performance of the analytical methods of a laboratory over time. The results show that most laboratories fell within the limits of +/- 15% bias for S-Creatinine above 100 mumol l-1 and +/- 17% for S-Urate at concentrations above 250 mumol l-1. Various steps to reduce the inter-laboratory variability are suggested, including numerical correction of individual laboratory results using correction functions. In a few laboratories, instability was too high to allow for numerical corrections of analytical results.

Bias↗
PubMed1996

Expert systems for the evaluation of data quality for establishing the Recommended Dietary Allowances.

In view of the important role that nutrient intake assessments play in establishing the Recommended Dietary Allowances (RDAs), the quality of food composition data must be assured for accuracy and representativeness. Assurance of data quality requires the definition of critical parameters in the data generation process and the evaluation of specific data for foods and components according to these parameters. An expert systems approach for evaluating the quality of analytical data has been developed by scientists at the Beltsville Human Nutrition Research Center to determine the quality of food composition data for five parameters: sampling plan, sample handling, number of samples, analytical method and analytical quality control. A rating scale for each parameter was developed with 0 representing poor or inadequately documented data and 3 representing optimal data. Specific criteria for each parameter and rating have been developed and incorporated into expert systems software to facilitate the objective assignment of ratings for each data source by the reviewer. After all ratings for a specific food-nutrient combination are assigned, the system calculates a composite score called the "confidence code" which indicates to the user the relative level of confidence in the data. By identifying and rating the important steps in the data generation process, one can begin to partition the possible sources of error or variability in the process. Limitation of the data set relative to specific purposes (e.g., setting the RDAs) can be identified. The evaluation process can provide the basis for focussed research to improve the most critical areas of the data generation process. A similar process could be established to evaluate the quality of analytical data for clinical measurements used to establish the RDAs.

Documentation↗
PubMed2003

Introduction and application of secured principal component regression for analysis of uncalibrated spectral features in optical spectroscopy and chemical sensing.

In this study, a novel chemometric algorithm for improved evaluation of analytical data is presented and applied to three spectroscopic data sets obtained by different analytical methods. This so-called secured principal component regression (sPCR) was developed for detecting and correcting uncalibrated spectral features newly emerging in spectra after finalizing the PCR calibration, which may result in major concentration errors. Hence, detection and correction of uncalibrated features is essential. Furthermore, detected uncalibrated features provide qualitative information for sensing and process monitoring applications indicating problems in the process flow. After conventional PCR calibration, sPCR analyzes measurement data in two steps: The first step investigates whether the obtained data set is consistent with the calibration model or not. If spectroscopic features are found that cannot be modeled by the principal components, they are extracted from the measurement spectrum. This corrected spectrum is then evaluated by conventional PCR. In the Experimental Section, sPCR was successfully applied to three data sets obtained by different spectroscopic measurements in order to corroborate general applicability of the proposed concept. For each data set, one of several substances was excluded from the calibration acting in the sPCR assessment as uncalibrated absorber. The test sets consisted of disturbed and undisturbed samples. A total of 109 out of 110 test samples were correctly classified as disturbed or undisturbed by an uncalibrated absorber. It was confirmed that the extracted disturbance spectra are in accordance with the spectra of the uncalibrated analytes. The concentration results obtained with sPCR were found to be equivalent to conventional PCR results in the case of undisturbed samples and more precise for disturbed samples.

Journal Article↗
PubMed2001

Seasonal and biological variation of urinary epinephrine, norepinephrine, and cortisol in healthy women.

BACKGROUND: There is a significant circadian and seasonal periodicity in various endocrine functions. The present study describes the within-day and seasonal fluctuation for urinary catecholamines and cortisol and estimates the within- (CV(i)) and between-subject (CV(g)) coefficients of variation for healthy women undertaking their routine work. In addition, index of individuality (I(i)) and power calculations were derived. METHODS: Eleven healthy females undertaking their routine life-style at work participated in the study. Each subject collected six samples during 24 h 15 days over a year, giving a total number of 990 samples. Using a random effect analysis of variance, we estimated CV(g) and total within-subject variation (CV(ti)), i.e. combined within-subject and analytical variation, from logarithmically transformed data. Analytical variation was subtracted from CV(ti) to give CV(i). CV(i) was estimated from samples collected monthly during 1 year (CV(iy)), weekly during 1 month (CV(im)), and six to eight times/day (CV(id)). RESULTS: A seasonal variation was demonstrated for excretion of epinephrine, norepinephrine, and cortisol standardized with creatinine. Concentrations of urinary epinephrine were higher during June and July compared to the rest of the year, whereas concentrations of urinary cortisol were higher during December and January compared to the rest of the year. Excretion of norepinephrine was lower during working hours and higher during hours off work for June and July compared to the rest of the year. There was a high within- and between-subject variation, which could not be explained by menstrual cycle, behavioral, emotional, or cognitive stress reactions. CONCLUSIONS: Despite high biological variation a reasonably low sample size, e.g. 10-50 individuals, is adequate for practical applicability, i.e. studying differences above 150%. The present study recommends to include the sampling time in the statistical evaluation of data and to be aware of the changes in diurnal variations over seasons. When single measurements are to be evaluated, reference intervals are recommended.

Adult↗
PubMed2000

Seasonal and biological variation of blood concentrations of total cholesterol, dehydroepiandrosterone sulfate, hemoglobin A(1c), IgA, prolactin, and free testosterone in healthy women.

BACKGROUND: Concentrations of physiological response variables fluctuate over time. The present study describes within-day and seasonal fluctuations for total cholesterol, dehydroepiandrosterone sulfate (DHEA-S), hemoglobin A(1c) (HbA(1c)), IgA, prolactin, and free testosterone in blood, and estimates within- (CV(i)) and between-subject (CV(g)) CVs for healthy women. In addition, the index of individuality, prediction intervals, and power calculations were derived. METHODS: A total of 21 healthy female subjects participated in the study. Using a random effects analysis of variance, we estimated CV(g) and total within-subject variation (CV(ti)), i.e., the combined within-subject and analytical variation, from logarithmically transformed data. Analytical variation was subtracted from CV(ti) to give CV(i). CV(i) was estimated from samples taken monthly during 1 year (CV(iy)), weekly during 1 month (CV(im)), and six times within 1 day (CV(id)). RESULTS: A cyclic seasonal variation was demonstrated for total cholesterol, DHEA-S, HbA(1c), prolactin, and free testosterone. Within-day variation was shown for prolactin and free testosterone. The overall mean values for the group and the variability (CV(iy) and CV(g)) were: 5.1 mmol/L, 13% [corrected], and 12% [corrected] for total cholesterol; 6.6 micromol/L, 20% [corrected], and 49% [corrected] for DHEA-S; 30% [corrected], 7.0% [corrected], and 7.5% [corrected] for HbA(1c)/hemoglobin(total); 2.1 g/L, 5.9%, and 13% for IgA; 136 mIU/L, 58% [corrected], and 63% [corrected] for prolactin; and 5.4 pmol/L, 55% [corrected], and 68% [corrected] for free testosterone. CONCLUSIONS: Collecting samples at specific hours of the day or times of the year may reduce high biological variation. Alternatively, the number of individuals may be increased and a paired study design chosen to obtain adequate statistical power.

Adult↗
PubMedDate not supplied

Development of a new series of agricultural/food reference materials for analytical quality control of elemental determinations.

Ten new Agricultural/Food Reference Materials--Bovine Muscle Powder (National Institute of Standards and Technology [NIST], code NIST RM 8414), Whole Egg Powder (NIST RM 8415), Microcrystalline Cellulose (NIST RM 8416), Wheat Gluten (NIST RM 8418), Corn Starch (NIST RM 8432), Corn Bran (NIST RM 8433), Whole Milk Powder (NIST RM 8435), Durum Wheat Flour (NIST RM 8436), Hard Red Spring Wheat Flour (NIST RM 8437) and Soft Winter Wheat Flour (NIST RM 8438)--were prepared by application of milling, irradiation, sieving, blending, and packaging procedures. Excellent material homogeneity was found for virtually all major, minor, and trace elements of interest. The reference materials were characterized with respect to elemental composition via an extensive international, interlaboratory characterization (certification) campaign. Chemical analyses conducted in 73 cooperating laboratories applying 13 major classes of independently different analytical methods led to 278 concentration values for 34 nutritionally, toxicologically, and environmentally pertinent elements. A total of 213 best-estimate and 65 informational concentration values are available for Al, As, B, Ba, Br, Ca, Cd, Cl, Co, Cr, Cs, Cu, F, Fe, Hg, I, K, Mg, Mn, Mo, N, Na, Ni, P, Pb, Rb, S, Sb, Se, Sr, Ti, V, W, and Zn. These products make a substantial contribution to the existing world repertoire of biological reference materials with respect to natural matrix and elemental composition. They are expected to be useful to analysts for quality control of analytical data. Applications include evaluations of analytical methods and instruments used in nutritional, toxicological, monitory, regulatory, environmental, agricultural, and other investigations. These products are available to the analytical community from the Standard Reference Materials Program, NIST, Gaithersburg, MD.

Analysis of Variance↗
PubMed2003

Statistical methods for longitudinal research on bipolar disorders.

OBJECTIVES: Outcomes research in bipolar disorders, because of complex clinical variation over-time, offers demanding research design and statistical challenges. Longitudinal studies involving relatively large samples, with outcome measures obtained repeatedly over-time, are required. In this report, statistical methods appropriate for such research are reviewed. METHODS: Analytic methods appropriate for repeated measures data include: (i) endpoint analysis; (ii) endpoint analysis with last observation carried forward; (iii) summary statistic methods yielding one summary measure per subject; (iv) random effects and generalized estimating equation (GEE) regression modeling methods; and (v) time-to-event survival analyses. RESULTS: Use and limitations of these several methods are illustrated within a randomly selected (33%) subset of data obtained in two recently completed randomized, double blind studies on acute mania. Outcome measures obtained repeatedly over 3 or 4 weeks of blinded treatment in active drug and placebo sub-groups included change-from-baseline Young Mania Rating Scale (YMRS) scores (continuous measure) and achievement of a clinical response criterion (50% YMRS reduction). Four of the methods reviewed are especially suitable for use with these repeated measures data: (i) the summary statistic method; (ii) random/mixed effects modeling; (iii) GEE regression modeling; and (iv) survival analysis. CONCLUSIONS: Outcome studies in bipolar illness ideally should be longitudinal in orientation, obtain outcomes data frequently over extended times, and employ large study samples. Missing data problems can be expected, and data analytic methods must accommodate missingness.

Bipolar Disorder↗
PubMed2000

Spirostanols obtained by cyclization of pseudosaponin derivatives and comparison of anti-platelet agglutination activities of spirostanol glycosides.

Naturally occurring saponins 3 and 4 have a normal type F ring and alpha-arranged CH(3)-21 group. Treatments of pseudosaponin peracetates 18 and 19 derived from 3 and 4, respectively, with alcoholic KOH, followed by acidification with acetic acid, gave spirostanols 20 and 22 having iso type F rings as major products. Structural analyses of sapogenins and saponins derived from pseudo derivatives 11, 12, 18 and 19 were performed by comparisons of their 1H-NMR spectral data and the X-ray analytical data of 3-O-p-bromobenzoyl sarsasapogenin 7, 3-O-acetyl diosgenin 13 and saponin 20. The mechanisms of ring-closure reaction of the side chain at C-22 of pseudosapogenins and pseudosaponins were deduced using stereomodels of the spirostanols derived from 11 under various reaction conditions. Inhibitory activities of saponin diglycosides 3, 4, 20, 21 and 25 on human platelet agglutinations induced by ADP and ristocetin were compared.

Adenosine Diphosphate↗
PubMed1997

Design of a study to improve accuracy in reading mammograms.

This paper is concerned with the design and analysis of mammography reading studies. In particular we consider studies aimed at evaluating interventions to improve the accuracy with which mammograms are read. A simple randomized design is suggested in which a relatively large group of readers read sets of mammograms before and after an intervention phase. We propose solutions to three difficult statistical issues that arise in the context of such studies: (i) the choice of primary outcome measure; (ii) the data analysis technique to be employed; and (iii) the methodology for calculating sample sizes for readers and images to be read. First, we argue in favor of using sensitivity and specificity as the primary outcome measures rather than receiver operating characteristic (ROC) curves in mammography studies, although the latter are considered state of the art for many types of radiology reading studies. We argue that sensitivity and specificity are more clinically relevant and conceptually more straightforward than ROC curves. Second, we suggest a bivariate approach to data analysis for evaluating intervention effects on sensitivity and specificity. This accommodates the correlations inherent between these measures and allows for estimation of joint effects on them. Finally we propose a method for power calculations that uses computer simulation techniques. Simple formulas for sample size calculations are not available in part because variability in accuracy amongst readers and variation in difficulty among images introduce complexity into power calculations. The simulation method that we propose accommodates such complexity and is easy to implement. The methodology was motivated by a study funded by the Department of Defense to evaluate the potential efficacy of an educational intervention. In the context of this study we illustrate the steps involved in power calculations and apply the data analytic techniques to the sort of data expected to result from this study. Though the proposed methods were motivated by this particular study, the statistical considerations are relevant more broadly in mammography and indeed in other types of radiologic imaging studies. Standards for the conduct of radiologic reading studies are not yet well developed, as they are for randomized clinical trials and for case-control studies. We hope that the discussion in this paper will add to the dialogue necessary for development of such standards.

Breast Neoplasms↗