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PubMedDate not supplied

The importance of considering spatial attributes in evaluating estuarine habitat condition: the South Carolina experience.

The South Carolina Estuarine and Coastal Assessment Program (SCECAP) was initiated in 1999 to assess the condition of the state's coastal habitats using multiple measures of water quality, sediment quality, and biological condition. Sampling was subsequently expanded to include components required for the National Coastal Assessment (Coastal 2000) Program. Habitats are classified as either "tidal creeks" (< 100 meters in width) or larger "open water" bodies. Approximately 30 sites are sampled within each habitat during the summer months using a probability-based random sampling design. Results obtained from the first two years of sampling documented significant differences in several water quality parameters (DO, salinity, pH, turbidity, fecal coliform bacteria, total nitrogen, TKN, total phosphorus) and biological measures (chlorophyll-a, finfish and crustacean abundance and biomass and a number of benthic species) between the tidal creek and open water habitats. These differences highlight the value of partitioning shallow water habitats separately from the larger open water bodies traditionally sampled in estuarine monitoring programs, especially since tidal creeks serve as critical nursery areas for many species. Based on the differences observed, there is a clear need to identify different physical and biological thresholds for evaluating the condition of each habitat type.

Animals↗
PubMed1995

A confidence interval for Pr(X < Y) - Pr(X > Y) estimated from simple cluster samples.

Distribution-free confidence intervals based on Somers' d (a simple function of the Mann-Whitney U statistic) are developed for Pr(X < Y) - Pr(X > Y), where X and Y are the ranks of any two observations from two independent populations. The approach accommodates a complex sampling design, and explicit formulas are given for simple cluster sampling. The method also accommodates simple progressive left- and right-censoring. The accuracy of the interval is shown to improve when the tanh-1 transform is used. A bootstrap solution was tried and did not perform as well as the proposed solution.

Analysis of Variance↗
PubMed1998

Reinfusion of discard blood from venous access devices.

PURPOSE/OBJECTIVES: To determine if clots are present in the initial 10 ml of blood routinely discarded from venous access devices (VADs) prior to blood sampling, and to determine if clots form in the discard blood specimen during the five minutes required to complete blood specimen sampling. DESIGN: A pretest/post-test design. SETTING: A large, mid-Atlantic research institution. SAMPLE: A convenience sample of 50 adult patients with cancer (27 males and 23 females) with a median age of 60. A large sampling size variation existed among the different VADs. METHOD: Two 5 ml discard specimens were drawn into separate syringes. Syringe #1 was filtered immediately, and syringe #2 was filtered after a five-minute dwell time. Both samples were filtered through a 40 micron filter. MAIN RESEARCH VARIABLE: The presence or absence of clots. FINDINGS: Fifty percent (n = 25) of the VADs had clots present on the filter from syringe #1. The clots varied in length, width, depth, and diameter, which precluded a consistent measurement. The investigators were able to measure either the diameter or length, depending on the shape of the clots. The majority of the clots (n = 17) appeared to be shaped like the lumen of a catheter and varied from 0.1 cm to 1.2 cm in length. Six clots were round and varied in diameter from 1.6 mm to 2.8 mm. Only 4% (n = 2) of the VADs had clots in syringe #2, but those clots were much larger, measuring 8.3 mm and 18.4 mm. CONCLUSIONS: The study addresses concerns of the investigators regarding the clinical practice of reinfusing discard blood obtained from VADs. Whether the clots present in the catheter and their reinfusion represent a significant risk to patient outcome is unclear. IMPLICATIONS FOR NURSING PRACTICE: Until further research is conducted and the degree of risk can be better defined, methods of drawing blood that require reinfusion of discard blood from VADs are not recommended.

Adult↗
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↗
PubMed1999

Assessing prenatal hepatitis B screening in Illinois with an inexpensive study design adaptable to other jurisdictions.

OBJECTIVES: This study estimated, using an economical survey design adaptable to other jurisdictions, the proportion of birth admissions in Illinois hospitals in which mothers were not screened for hepatitis B surface antigen prior to delivery. It also identified factors associated with lack of screening. METHODS: Based on a cluster sampling design, 1372 birth records were sampled, and data were abstracted by local personnel at 56 hospitals. Selected data elements were reabstracted on a subsample to evaluate recording errors. RESULTS: Reabstracted data demonstrated 95% agreement among reviewers. Hepatitis B surface antigen screening was documented for 90.7% of mothers; 11% of responding hospitals accounted for 45% of nonscreened mothers. Risk factors for not being screened included no prenatal care, Medicaid or no insurance, and delivery at a hospital lacking a written hepatitis B surface antigen policy. CONCLUSIONS: In Illinois, prenatal hepatitis B surface antigen screening rates were high and similar to those in other states. Births without screening or transferred information clustered in a few hospitals. The methods used here can economically identify underscreened populations by sampling a large number of hospitals within designated areas.

Cluster Analysis↗
PubMed2004

An update on laboratory productivity with infectious disease assays on the Bayer ADVIA Centaur Immunoassay System.

New biological materials and advances in robotic and computer technologies have enabled the development of automated systems designed for high-performance infectious disease immunoassays and nucleic acid amplification. The fully automated, random access Bayer ADVIA Centaur immunoassay system, offering testing for fertility, therapeutic drug monitoring, infectious disease, allergy, cardiovascular, anemia, oncology, TDMs and thyroid, has been specifically designed for use in large-volume laboratories. New immunoassay tests have been developed for the ADVIA Centaur for the hepatitis A virus, hepatitis B virus, hepatitis C virus and HIV. These assays have undergone extensive performance evaluation using samples designated in the CTS in support of obtaining the Communautés Européennes (CE) mark for European market distribution. The ADVIA Centaur Immunoassay System represents an optimal platform for infectious disease testing because of its flexibility in allowing many different assay formats and protocols with multiple incubation steps and washes coupled with its combination of magnetic particle separation and chemiluminescent detection. Additional quality features of the system design are the sample integrity verification/check, the use of disposable sample pipette tips, clot detection, the ability for sensing liquid levels, the reagent aspiration verification/check, the automatic cascade reflex testing, repeat testing, and automated reagent inventory. The ADVIA Centaur has a maximum test throughput of 240 tests per hour. Minimal hands-on time is required as a result of the large onboard capacity for reagents and supplies combined with automated maintenance and monitoring features, which streamline operations and result in a walk-away through-put of up to 840 tests.

AIDS Serodiagnosis↗
PubMed1997

Estimating means and percentages in a complex sampling survey: application to a French national survey on sexual behaviour (ACSF). Analyse des Comportements Sexuels en France.

Two-phase stratification sampling with unequal selection probabilities is a relatively cost-efficient strategy to address problems on a nationwide basis and to perform comparative analyses of specific subgroups. This was the case with the ACSF survey. Specific procedures to estimate the variances of unbiased estimators in complex sampling designs are not included in standard statistical packages and no specialized software is available for two-phase sampling. A detailed synthesis of general basic rules for inference about a target population from a probability sample is first presented. We follow with a standard procedure to estimate means and percentages with their confidence intervals according to the design. Finally, numerical results are discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1999

National probability samples in studies of low-prevalence diseases. Part I: Perspectives and lessons from the HIV cost and services utilization study.

OBJECTIVE: To examine the trade-offs inherent in selecting a sample design for a national study of care for an uncommon disease, and the adaptations, opportunities and costs associated with the choice of national probability sampling in a study of HIV/AIDS. SETTING: A consortium of public and private funders, research organizations, community advocates, and local providers assembled to design and execute the study. DESIGN: Data collected by providers or collected for administrative purposes are limited by selectivity and concerns about validity. In studies based on convenience sampling, generalizability is uncertain. Multistage probability sampling through households may not produce sufficient cases of diseases that are not highly prevalent. In such cases, an attractive alternative design is multistage probability sampling through sites of care, in which all persons in the reference population have some chance of random selection through their medical providers, and in which included subjects are selected with known probability. DATA COLLECTION AND PRINCIPAL FINDINGS: Multistage national probability sampling through providers supplies uniquely valuable information, but will not represent populations not receiving medical care and may not provide sufficient cases in subpopulations of interest. Factors contributing to the substantial cost of such a design include the need to develop a sampling frame, the problems associated with recruitment of providers and subjects through medical providers, the need for buy-in from persons affected by the disease and their medical practitioners, as well as the need for a high participation rate. Broad representation from the national community of scholars with relevant expertise is desirable. Special problems are associated with organization of the research effort, with instrument development, and with data analysis and dissemination in such a consortium. CONCLUSIONS: Multistage probability sampling through providers can provide unbiased, nationally representative data on persons receiving regular medical care for uncommon diseases and can improve our ability to accurately study care and its outcomes for diseases such as HIV/AIDS. However, substantial costs and special circumstances are associated with the implementation of such efforts.

Data Collection↗
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↗
PubMed1999

An alarming lack of public awareness towards oral cancer.

OBJECTIVE: To determine public awareness and knowledge of oral cancer in Great Britain. DESIGN: The respondents were selected according to a systematic probability sample designed to be representative of all adults in Great Britain (GB). The overall design was similar to previous omnibus surveys carried out by National Opinion Poll (NOP). The survey was carried out in ten regions of GB in September 1995 and was commissioned by the Health Education Authority (HEA). SUBJECTS AND METHODS: A random sample of 1,894 members of the public over the age of 16 years were asked in face-to-face interviews their knowledge relating to cancer, with particular reference to oral cancer, its causes and those at high risk and general attitudes to cancer. RESULTS: Oral cancer was one of the least heard of cancers by the public with only 56% of the participants being aware, whereas 96% had heard of skin cancer, 97% lung cancer and 86% cervical cancer. There was a 76% awareness of the link between smoking and oral cancer but only 19% were aware of its association with alcohol misuse. Whereas 94% agreed that early detection can improve the treatment outcome, a disheartening 43% believed that whether a person developed a cancer or not was a matter of chance and therefore was unavoidable. CONCLUSIONS: This survey highlights a general lack of awareness among the public about mouth cancer and a lack of knowledge about its causation especially the excess risk associated with alcohol. RECOMMENDATIONS: There is a clear need to inform and educate the public in matters relating to the known risk factors associated with oral cancer. A media campaign informing the public about oral cancer is clearly required. The need for the reduction in the incidence of oral cancer should be included in 'Our healthier nation' targets. An overall health promotion strategy to reduce cancers should include oral cancer as a priority. In addition the European Code against Cancer which aims to improve prevention, the early detection of oral cancer and the necessity for fast track referral should be made more widely known. Recognition of oral cancer in local strategies for oral health should be encouraged.

Adolescent↗
PubMed1994

Optimal sampling theory: effect of error in a nominal parameter value on bias and precision of parameter estimation.

The authors examined the robustness of optimal sampling theory in estimating the parameter values of two different populations of patients receiving a constant rate, half-hour intravenous infusion of theophylline. One population consisted of smokers; the other included nonsmokers. The smoking population was predicted to have a serum clearance approximately 50% greater than the nonsmokers because of an induction of the cytochrome P450 system. After an initial study to provide both patient-specific and population mean parameter values, optimal sampling strategies that were derived from each population (seven sample split designs) and the patient's seven sample and four sample design were determined. A second study was performed with an overall sampling strategy that was superset of all the above strategies. The analysis of all samples served as the reference for the parameter values. Bias and precision of the values determined with each of the optimal sampling sets (seven sample sets based on the "correct" and "wrong" populations, the patient's seven and four sample sets) were determined relative to these reference values. Irrespective of the sample set used for analysis, unbiased and precise parameter estimates, particularly of hybrid parameters were provided. With the patient's four sample set, Vss was significantly biased, but the value of (2.2%) was clinically insignificant. The authors conclude that optimal sampling theory, as implemented in this study, provides robust estimates of important pharmacokinetic parameter values, even when errors of 50% are present in the clearance of the population used to calculate the optimal sampling design.

Adolescent↗
PubMed2005

Design considerations in the sequential analysis of matched case-control data.

A role for sequential test procedures is emerging in genetic and epidemiological studies using banked biological resources. This stems from the methodology's potential for improved use of information relative to comparable fixed sample designs. Studies in which cost, time and ethics feature prominently are particularly suited to a sequential approach. In this paper sequential procedures for matched case-control studies with binary data will be investigated and assessed. Design issues such as sample size evaluation and error rates are identified and addressed. The methodology is illustrated and evaluated using both real and simulated data sets.

Breast Neoplasms↗
PubMed2002

Randomized, placebo-controlled, parallel group versus crossover study designs for the study of dementia in Parkinson's disease.

In studies of dementia, crossover designs are controversial, reflecting concerns about temporal stability of disease, confounding of treatment effects with period by treatment interactions and/or carryover effects. Carryover effects are differences in the lingering effect of treatments (placebo) into subsequent periods. In the context of a trial to study the effect of donepezil on dementia in patients with Parkinson's disease, we examine two-sequence crossover studies with two or four periods, and a four-sequence design with two periods. We quantify bias in estimated treatment effects due to carryover effects and explore the use of biased estimators in hypothesis testing. For hypothesis testing, type I error rates are valid if (1) repeated administration of treatment alters the outcome only for effective treatments and (2) carryover effects due to placebo following treatment periods are nonzero only for effective treatments. For crossover and parallel group designs, sample sizes are adjusted for reduced statistical power due to carryover effects and temporal changes in variance. For the proposed clinical study, we estimate that a single-period parallel group design with baselines would require 104 patients and take about 23 months to complete. A two-sequence, four-period parallel group design with baselines would require about 80 patients and about 20 months to complete. We conservatively assume a carryover effect of 50% of the treatment effect for a two-sequence four-period crossover design. The estimated treatment effect for this model may underestimate the true treatment effect by up to 13%. The sample size/study length requirements are 28 patients or 12.4 months, respectively, a substantial saving over either parallel group design. The cost of allowing for carryover in the sample size calculation is about 1.2 months of study time.

Bias↗
PubMedDate not supplied

The behavioral risk factor surveys: II. Design, methods, and estimates from combined state data.

Behavioral risk factor (BRF) telephone surveys were conducted by 28 states and the District of Columbia from April 1981 through October 1983 to obtain baseline prevalence estimates for risk factors associated with the leading causes of death among adults. A supplemental survey was conducted to cover the remaining states (except Hawaii) in order to provide individual states with national-level data for comparison purposes. The complex sampling designs and variable sampling rates among state surveys required the computation of sample weights before estimates on a national level could be made. Estimates from the combined individual surveys are similar to those obtained from more expensive in-person interviews. The BRF national prevalence estimate of chronic heavier drinking is 8.7 percent, equivalent to the 1979 National Institute on Alcoholism and Alcohol Abuse (NIAAA) estimate of 9 percent. The BRF estimate of 31.5 percent for current smokers compares closely with the 32.6 percent estimated by the 1980 Health Interview Survey. Despite recognized technical limitations, this type of telephone survey can be a practical and affordable source of information both for initially gathering prevalence data and for monitoring trends in the prevalence of behavioral risk factors of public health concern.

Adult↗
PubMed2005

A note on P-values under group sequential testing and nonproportional hazards.

Group sequential designs are often used for periodically assessing treatment efficacy during the course of a clinical trial. Following a group sequential test, P-values computed under the assumption that the data were gathered according to a fixed sample design are no longer uniformly distributed under the null hypothesis of no treatment effect. Various sample space orderings have been proposed for computing proper P-values following a group sequential test. Although many of the proposed orderings have been compared in the setting of time-invariant treatment effects, little attention has been given to their performance when the effect of treatment within an individual varies over time. Our interest here is to compare two of the most commonly used methods for computing proper P-values following a group sequential test, based upon the analysis time (AT) and Z-statistic orderings, with respect to resulting power functions when treatment effects on survival are delayed. Power under the AT ordering is shown to be heavily influenced by the presence of a delayed treatment effect, while power functions corresponding to the Z-statistic ordering remain robust under time-varying treatment effects.

Algorithms↗
PubMedDate not supplied

[Survey of what is published on Italian nursing journals].

Nursing research is an important activity for nurses; the main aim is to improve the quality of nursing. Several national and european laws have been issued about it. To develop knowledge about nursing, nurses have to understand the results of researches, implement them in the different situation and sometimes carry out researches. The results can be published in nursing journals which a lot of nurses use to share information. This study reviewed the characteristics of research articles published in italian nursing journals from 1998 to 2003. Phenomena of interest are: areas of enquiry, investigators, methods, research design, sampling and means to gather data. 122 articles have been reviewed: 78% focus on clinical aspects, 55% were carry out by nurses, 92% adopt the quantitative approach, 90% used non experimental design, 89% used convenience selection sampling method and 58% answer ways. The characteristics of this study are similar to other studies about italian nursing publication. There are some limits in this type of literature: lower generalization because of lower representativeness of sample, convenience selection sampling method, and higher risk of interference due to frequent use of non experimental design. However the number of italian nurses that carry out researches is increasing and nursing is the most studied area.

Italy↗
PubMed2000

Perceived knowledge and training needs in adolescent pregnancy prevention: results from a multidisciplinary survey.

OBJECTIVES: To examine health care professionals' knowledge and interest in training in adolescent pregnancy prevention and whether an association exists between perceived knowledge and interest in training. DESIGN: A cross-sectional mailed survey. PARTICIPANTS: Random, stratified sample design that identified 800 psychologists, 800 social workers, 1,000 nurses, and 400 pediatricians from national professional membership lists. Response rate to the mailed survey was 51%. After removing respondents who did not currently work with adolescents, 1,242 surveys (41%) were available for analyses. MAIN OUTCOME MEASURES: Descriptive analyses were conducted on self-report data concerning perceived knowledge and interest in training about adolescent pregnancy prevention separately for each of the 4 disciplines. Within disciplines, perceived knowledge and interest in training were correlated for each of 3 content areas (ie, sex education and contraceptive counseling, adolescent pregnancy, and counseling after a negative pregnancy test) and for a summary measure of the content areas. RESULTS: Less than half of the nursing, pediatrics, psychology, and social work professionals reported high perceived knowledge in the 3 content areas. Psychologists and social workers reported the lowest perceived knowledge. However, with the exception of psychologists, more than two thirds of the other respondents reported moderate or high interest in training in the 3 content areas. Interest in training was not strongly correlated with perceived knowledge within any discipline. CONCLUSIONS: The need to integrate psychosocial components into adolescent health care is a core assumption in the field, yet these data indicate that psychologists and social workers perceive low levels of knowledge and interest in training. These disciplines may benefit from more targeted professional training about their role in preventing adolescent pregnancy.

Adolescent↗
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↗