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PubMedDate not supplied

[Methodology of the National Seroepidemiologic Survey, Mexico].

This paper briefly describes the methodology employed in the National Seroepidemiologic Survey (NSS). Among the aspects discussed are: previous studies of this kind; the master sampling frame; the sample design, the study population and sample size; the selection of diseases for study; the variables; instruments for data collection; operational design for the survey; as well as data processing and analysis. The overall response rate of the NSS was 78.4 per cent of the surveyed homes, 40 per cent of which were from rural areas (communities of less than 2,500 persons). The non-response rate was 41.3 per cent with the highest level in Baja California Sur (RNR = 26%) and the lowest in Puebla (RNR = 50.9%). The poor response in Puebla may have been due to the fact that it was the first state surveyed and served as the pilot project. The variable estimates from the NSS were similar to those found in other national surveys and the General Population Census. Therefore, these is reason to believe that the results of the NSS were representative and comparable. The final part of the paper describes the NSS projects already published, national seroprevalences, considerations concerning inference, and the laboratory procedures utilized in each project.

Adolescent↗

PubMed1990

Estimating the infectivity of HIV from partner studies.

The main sources of data for estimating infectivity of the human immunodeficiency virus (HIV) come from studies of the susceptible partners of individuals known to be infected with HIV. Estimation of infectivity from these studies is complicated by limitations imposed by the sampling designs. This paper reviews three sampling schemes that have been used in partner studies and, for each, proposes methods for estimating various theoretic models for infectivity. The methods, as well as procedures for checking goodness-of-fit, are illustrated using data from a study by Peterman and colleagues.

Acquired Immunodeficiency Syndrome↗

PubMed1991

Utility and predictive value of a rapid measurement of urinary pregnanediol glucuronide by enzyme immunoassay in an infertility practice.

STUDY OBJECTIVE: To assess the clinical utility of measuring urinary pregnanediol glucuronide in random samples in an infertility practice. DESIGN: Samples of urine were collected from patients approximately 3 weeks from their last menstrual period to ascertain if ovulation had occurred. Each sample was tested for specific gravity before analyzing for pregnanediol glucuronide. Simultaneous venipuncture was performed to compare results from the urinary assay to quantitative measures of serum progesterone (P). SETTING: All patients were randomly sampled. PATIENTS: Three hundred ninety women undergoing pituitary down regulation with leuprolide acetate were chosen for study because they routinely initiate medication after documentation of ovulation. OUTCOME MEASURES: The performance of the urinary pregnanediol glucuronide was evaluated as to its sensitivity, specificity, predictive value, and test efficiency compared with a serum measurement of 2.5 ng/mL and 10.0 ng/mL. RESULTS: The performance characteristics of the pregnanediol glucuronide assay were directly related to the hydration status of the patient at the time of sample collection. Regardless of urine specific gravity, if pregnanediol glucuronide was qualitatively detected (greater than 3 micrograms/mL), serum P was greater than 2.5 ng/mL. However, in cases in which pregnanediol glucuronide was undetected (less than 3 micrograms/mL), results were only accurate when the specific gravity was greater than or equal to 1.020. When comparing urinary pregnanediol glucuronide values to serum greater than 10 ng/mL, both specificity and predictive value of a positive test decreased because of increased numbers of false-positive results. CONCLUSIONS: The enzyme immunoassay measurement for pregnanediol glucuronide may replace the use of serum P in documenting the ovulatory status of many patients. However, all specimens must be checked for specific gravity and if less than 1.020, a serum P should be used to ensure accuracy.

Female↗

PubMed1991

National Survey of Family Growth: design, estimation, and inference.

The purpose of this report is to document the procedures used in the 1988 National Survey of Family Growth (NSFG) to select the sample, weight the data to produce national estimates, impute missing data, and estimate sampling errors. Therefore, this report necessarily contains a great deal of technical detail. For readers who do not need this level of detail, this summary briefly describes the procedures used. The National Survey of Family Growth is conducted every few years by the National Center for Health Statistics (NCHS), a part of the U.S. Department of Health and Human Services. The purpose of the survey is to collect and publish data from a national sample of women on childbearing, factors affecting childbearing (such as contraception, sterilization, and infertility), and related aspects of maternal and infant health. Interviewing for Cycle IV of the survey was done in 1988 by Westat, Inc., under a contract with NCHS. Personal interviews were conducted between January and August of 1988 with a national sample of 8,450 women in the civilian noninstitutionalized population of the United States. Interviews were conducted in person by trained female interviewers and lasted an average of 70 minutes. The interview focused on the woman's pregnancies, if any; her use of contraception; her ability to bear children (fecundity and infertility); her use of medical services for family planning, infertility, and prenatal care; her marriage and cohabitation history, if any; and a wide range of demographic and economic characteristics. This report describes some of the main methodological aspects of the survey, including the sample design, weighting, sampling errors, and imputation of missing data. These topics will be described briefly and less technically in this summary. Each topic is discussed in more detail in the rest of the report.

Adolescent↗

PubMedDate not supplied

[The national addictions survey of Mexico].

A probabilistic household survey was made with the following objectives: to estimate the prevalence of consumption of tobacco, alcohol and legal and illegal drugs; to identify attitudes and values, risk factors and problems associated with the consumption of addictive substances in a population from 12 to 65 years old, which resides in the urban areas of Mexico. This survey forms part of the National Health Surveys System, and its sample design is based on the Master Sample Framework of the National Health Surveys System, which gathered information representative of the national population and for seven regions. In the elaboration of the questionnaire indicators proposed by the World Health Organization (WHO), validated for Mexico, were used as well as previous knowledge about the topic. Thirteen thousand and five interviews were made, of which 96.7 per cent were complete and 2.6 per cent were rejected. In the group from 12 to 17 years old, 32 per cent of the men and 23 per cent of the women already consumed alcoholic drinks. The age group with the largest proportion of men who were frequent drinkers is from 30 to 39 years of age, with 36.3 per cent. For women 34.0 per cent of the frequent drinkers were found in the 40 to 49 year age group. It was found that six per cent of the population from 18 to 65 years of age is alcohol dependent, 12.5 per cent of men and less than one per cent of women. The population which smokes reaches 26 per cent of the total, with 38.3 per cent of men and 14.4 per cent of women. Forty two and four per cent of smokers are from 18 to 29 years of age. Among the daily smokers, 17 per cent were considered dependent on cigarettes. Only 4.8 per cent of the population admits having consumed some type of drug on at least one occasion, with the men from 12 to 34 years old being the age group which is most affected by the use of drugs (8.5%). Active users in the last year made up 2.1 per cent and in the last month the proportion of active users was less than one per cent. The most frequently used drug was marihuana (1%), the second used were tranquilizers (0.4%), and the third most frequently used were inhalants (glue, thinner) (0.26%). The most commonly consumed drug by male users was marihuana and by female users the most commonly used drug was stimulants.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1989

Biostatistics in clinical trials: Part 2. Determining sample sizes for clinical trials.

The appropriate sample size for a clinical trial depends on the objectives of the trial. For Phase II trials, the recommended sample size is generally in the neighborhood of 25-40 patients, regardless of the choice of design. Sample sizes for Phase III trials are much more variable, ranging from less than a hundred to thousands of patients. The methodology of sample size determination for Phase III trials depends on the type of endpoint that is to be the primary focus of analysis. Tables of sample sizes for a variety of situations are presented. Use of sequential designs may reduce the required sample size by permitting early termination of trials whose results become definitive prior to completion of patient entry.

Clinical Trials as Topic↗

PubMed2026

Haplotype Blocks Are Associated With Rapid Local Adaptation to Environmental Shifts in Wild Barley.

Genomic mechanisms of local adaptation must be highly responsive in geographic regions where climate is changing rapidly. The Levant region is a critical biodiversity hotspot and the distribution edge for many species, including the wild ancestor of domesticated barley. This region is under an accelerated desertification process, thus enforcing a rapid genomic response to the projected environmental changes. To elucidate the genomic basis of rapid local adaptation, we studied wild barley populations using an ecological-genetic sampling design that decouples environmental variation from demographic background. We collected and sequenced 300 wild barley individuals and evaluated the phenotypes of 3600 progeny plants over 3 years. Our genomic analyses revealed that local adaptation is associated with clusters of candidate genes forming haplotype blocks. These clusters are enriched with environment and stress responsive genes, including flowering time regulators, drought and heat responsive genes. We identified six candidate adaptive haplotype blocks which span 1-8 Mbp and are distributed across chromosomes 1H, 2H, 4H and 5H, each segregating as two major haplotypes. Additionally, we integrated over 2600 occurrence records into ecological and evolutionary modelling to assess the genomic vulnerability of populations to projected future climates. Our study identifies candidate genomic regions and environmental drivers of local adaptation in wild barley and highlights the advantage of haplotype blocks architecture in orchestrating an efficient response to rapid environmental change. We highlight the ecological factors most strongly associated with the observed evolutionary responses and provide insights and guidelines for biodiversity conservation and implementation of crop wild relatives in breeding.

Hordeum↗

PubMed1990

Experimental design and efficient parameter estimation in population pharmacokinetics.

A computer simulation technique used to evaluate the influence of several aspects of sampling designs on the efficiency of population pharmacokinetic parameter estimation is described. Although the simulations are restricted to the one-compartment one-exponential model, they provide the basis for a discussion of the structural aspects involved in designing a population study. These aspects include number of subjects required, number of samples per subject, and timing of these samples. Parameter estimates obtained from different sampling schedules based on two- and three-point designs are evaluated in terms of accuracy and precision. These simulated data sets include noise terms for both inter- and intraindividual variability. The results show that the population fixed-effect parameters (mean clearance and mean volume of distribution) for this simple pharmacokinetic model are efficiently estimated for most of the sampling schedules when two or three points are used, but the random-effect parameters (describing inter- and intraindividual variability) are inaccurate and imprecise for most of the sampling schedules when only two points are used. This drawback was remedied by increasing the number of data points per individual to three.

Computer Simulation↗

PubMed1979

Geochemical surveys in the United States in relation to health.

Geochemical surveys in relation to health may be classified as having one, two or three dimensions. One-dimensional surveys examine relations between concentrations of elements such as Pb in soils and other media and burdens of the same elements in humans, at a given time. The spatial distributions of element concentrations are not investigated. The primary objective of two-dimensional surveys is to map the distributions of element concentrations, commonly according to stratified random sampling designs based on either conceptual landscape units or artificial sampling strata, but systematic sampling intervals have also been used. Political units have defined sample areas that coincide with the units used to accumulate epidemiological data. Element concentrations affected by point sources have also been mapped. Background values, location of natural or technological anomalies and the geographic scale of variation for several elements often are determined. Three-dimensional surveys result when two-dimensional surveys are repeated to detect environmental changes.

Air Pollutants↗

PubMed1977

[Determination of a small amount of acrylamide in air (author's transl)].

According to the recently published "Guidebook of Measuring Method for Environmental Atmosphere" edited by the Department of Safety and Health Labour Administration of Japan, it is recommended to determine acrylamide (AAM) in air by sampling with glass fiber filter, extracting into methanol and injecting in the FID gaschromatograph (GC). Although acrylamide particle may be measured by this method, it is questionable whether a small amount of gaseous acrylamide could be determined together. We have investigated the determination of a small amount of acrylamide monomer in air by sampling it on solid adsorbent packed in a specially designed sampling tube. We concluded that it is capable to determine a small amount of acrylamide in air, by using the above mentioned sampling tube packed with Flusin-F (treated with phosphoric acid; 30--60 mesh) as the solid adsorbent, at the concentration range from 1.0 to 0.01 ppm (v/v), and the recovery rate of 82--83%.

Acrylamides↗

PubMed1990

New estimates of traumatic SCI prevalence: a survey-based approach.

New estimates of traumatic spinal cord injury (SCI) prevalence are developed from a survey specifically designed to identify the SCI population in both institutional and non-institutional settings. The survey utilised a mixed-mode sampling design based on probability sampling methods. Detailed interviews were conducted with SCI persons identified in this survey. We estimate that the traumatic SCI prevalence rate in the United States is 721 cases per million, and that there are about 177,000 SCI persons residing in the United States.

Epidemiologic Methods↗

PubMedDate not supplied

Maternity blues research: a critical review.

Maternity blues research from 1962, when the first study was published, to the present is critically evaluated. Each study that met the sample criteria was judged against the following categories: measurement, research designs, sampling, and clinical description. Two major weaknesses in blues research were identified: (1) lack of standardized instruments for the measurement of the incidence, severity, and duration of the blues and (2) inconsistencies in research design.

Depressive Disorder↗

PubMedDate not supplied

Cell loss and shrinkage in the nucleus basalis Meynert complex in Alzheimer's disease.

Marked neuron loss in the nucleus basalis of Meynert complex (NBMC) in Alzheimer's disease has repeatedly been reported in the literature. However, most of these studies quantitated only magnocellular, hyperchromatic (putative cholinergic) neurons of just a small part of the NBMC, and counts were expressed as numerical density. Applying a 3-dimensional-sampling design throughout the entire rostrocaudal extent of the NBMC and sampling neurons regardless of their size and staining characteristics, an overall neuron loss of only 15.5% was demonstrated for the whole NBMC. Neuron loss varied from 0% rostrally in the NBMC up to 36% in the most caudal part of the nucleus basalis of Meynert. Moreover, a significant increase in the number of small-sized neurons and a significant decrease in the number of large, putative cholinergic neurons could be detected, suggesting that apart from neuron loss neuron shrinkage appears to be another characteristic neuropathological feature of this degenerating cholinergic NBMC system. Preservation of these magnocellular cholinergic neurons in shrunken form renders it likely that cholinergic dysfunction, characteristic of Alzheimer's disease, may be responsive to neurotrophic influences.

Aged↗

PubMed1991

A measuring technique for the investigation of the dielectric behaviour of biological tissue at low temperatures.

The experimental technique described can be used to measure the complex dielectric constant of different kinds of samples in the temperature range T = 300 to 4K. The specially designed sample holder guarantees simple preparation and allows in-vitro measurements of biological tissues as well as investigations of related materials of interest including liquids. The results of fatty tissue chosen as a model substance will be shown and discussed in comparison to simple basic compounds in subsequent papers.

Electric Conductivity↗

PubMed1979

An investigation of coronary heart disease in families. The Framingham offspring study.

The Framingham Heart Study (FHS) was started in 1948 as a prospective investigation of cardiovascular disease in a cohort of adult men and women. Continuous surveillance of this sample of 5209 subjects has been maintained through biennial physical examinations. In 1971 examinations were begun on the children of the FHS cohort. This study, called the Framingham Offspring Study (FOS), was undertaken to expand upon knowledge of cardiovascular disease, particularly in the area of familial clustering of the disease and its risk factors. This report reviews the sampling design of the FHS and describes the nature of the FOS sample. The FOS families appear to be of typical size and age structure for families with parents born in the late 19th or early 20th century. In addition, there is little evidence that coronary heart disease (CHD) experience and CHD risk factors differ in parents of those who volunteered for this study and the parents of those who did not volunteer.

Adult↗

PubMed2026

Non-smoked cannabis consumption formats and Cannabis Use Disorder severity in an illicit setting: Evidence from Chile, 2020-2024.

BACKGROUND: Cannabis Use Disorder (CUD) has become an increasing public health burden, particularly in Chile. Non-smoked cannabis formats and products have been independently associated with CUD but remain understudied in the region. This study compares CUD severity among individuals aged 12 to 65 in Chile who consume cannabis via edibles, vaporization or both versus those who exclusively smoke it. METHODS: We obtained secondary data from three waves of the Chilean National Survey on Drugs in the General Population (ENPG), a three-stage stratified probabilistic sampling design study conducted in 2020, 2022, and 2024. Our pooled cross-sectional sample included individuals (n = 3543) who reported cannabis use in vaped, edible, both vaped and edible or exclusively smoked format in the past 12 months. We used a partial proportional odds model to estimate the association between CUD severity and consumption formats. RESULTS: Cannabis vaping group showed higher odds of presenting at least mild CUD (OR = 6.21 [95% CI: 3.75-10.3]), as did the edible group (OR = 1.73 [95% CI: 1.08-2.78]) and both group (OR = 5.92 [95% CI: 2.72-12.87]), compared to exclusive smokers. However, only the vaped group demonstrated higher odds for all severity levels. CONCLUSION: Compared with exclusive smokers, users of vaporizers and/or edibles showed a stronger association with CUD. This association may be explained by consumption patterns and total THC exposure. Further research is needed to characterize the average THC exposure by consumption format, acknowledging contextual confounders such as the legal framework.

Humans↗

PubMed1991

Outcome of 1500 consecutive chorionic villus samplings.

OBJECTIVE: To evaluate the clinical complications and diagnostic problems of chorionic villus sampling. DESIGN: A pragmatic retrospective analysis. SETTING: Tertiary obstetric referrals mostly to private practice; sampling carried out at Royal Prince Alfred Hospital; diagnostic analysis usually at Oliver Latham Laboratory, or the Clinical Immunology Research Centre, Royal Prince Alfred Hospital, New South Wales. PATIENTS: 1500 women in the first trimester of pregnancy requesting prenatal diagnosis because of a risk of chromosomal or inherited genetic disorder in the fetus. INTERVENTIONS: Ultrasound-guided passage of a catheter into the chorion through the cervix. MAIN OUTCOME MEASURES: Incidence of unintended abortion, preterm births, low weight infants and discrepant karyotypes. RESULTS: There were 42 unintended abortions (3.0%), about 0.4% higher than the background abortion rate in women of similar age. Abortion did not occur more frequently in women with vaginal bleeding earlier in that pregnancy. Rates of preterm births and birth of low birthweight infants did not differ from the general population. A second diagnostic test was required in 68 women (4.5%). Mosaicism and tetraploidy were usually confined to the chorion. CONCLUSION: Chorionic villus sampling is an acceptable diagnostic test. Amniocentesis should be offered to patients who show mosaicism or tetraploidy.

Abortion, Spontaneous↗

PubMed1976

Utilization of dental services in the adult Danish population 1975.

Lack of information on the dental behavior of adults in Denmark has become a major problem in the national planning of dental services. The purpose of this study was to establish the pattern of utilization of dental services among adult Danes (aged 15 and above). A three-stage cluster sampling design covering the total adult population of Denmark was used to draw a representative sample comprising 1,600 persons. Household interviews by trained interviewers were carried out. Of the adults interviewed, 58% reported yearly dental visits the last 5 years, 32% had not seen a dentist or only when in pain, and 10% went irregularly. Differences according to place of living, age, sex, occupation and school dental care were found. 63% of those who had seen a dentist reported bad teeth or were edentulous with or without dentures. 10% reported fear, 9% had good teeth and 5% reported economic difficulties. The most frequent treatments at the latest dental visit were cleaning and filling for the regular patients and extractions and dentures for the nonregular patients. A multiple classification analysis revealed that the number of teeth was the strongest predictor for dental services, with the following predictors in descending order: age, occupation, place of living, economy, sex and school dental care. These variables could explain 58% of the variation in utilization.

Adolescent↗