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Screenings for the genetic disorder alpha(1) antitrypsin deficiency (AAT Deficiency) have been one of two models: large screenings of general populations and small targeted detection programs in high-risk groups. The most appropriate screening and detection methodologies in terms of target populations, subject participation and yield of positive tests, however, have not been well defined. The major objective of this pilot study was to evaluate the effectiveness in terms of participation of two different AAT Deficiency detection programs using a self-administered fingerstick blood test. Individuals ages 30-60 under the care of a pulmonary physician and with a diagnosis of emphysema, COPD, chronic bronchitis, or bronchiectasis were the targeted population. Participants were offered AAT Deficiency testing in the pulmonary physician's office compared with testing offered through mail. Participation (i.e., frequency of subject participation in the detection program) of two different AAT Deficiency detection programs. Non-participation was due to fear of self-administered testing and research studies; women were more likely to participate than men. Eligible subjects were significantly more likely to participate when offered testing by their pulmonary physician in-office (83%) than mail-only (42%) (P < 0.02). Although self-administered genetic testing is available, highest participation in AAT Deficiency detection program was found when offered directly by the physician. This finding may have implications for screening and detection of other genetic diseases. Future studies need to evaluate the yield (i.e., frequency of positive tests) of these detection methodologies in highly targeted populations.
The target population is a key concept for the planning and evaluation of health services. However, in developing countries, health professionals in the field are often uneasy with the determination of the population denominator. In Zaire, where reliable demographic data are hardly available, we make use of two different methods aimed to the determination of the size of the target population: (1) an exhaustive population based survey performed by trained interviewers, and (2) a rapid census of the target population performed by community health workers. This paper presents both the results of a demographic survey organized in 1984, and two consecutive census performed by community health workers in 1986 an 1988, in the same area (Northern-Kivu, Zaire). Our results suggest that community health workers under close supervision are able to perform rapidly and at low cost a reliable collection of the demographic data needed for the implementation and monitoring of health programmes at the local level.
One difficulty in estimating the target population for public health programs is identifying a current and appropriate indicator of the low-income population. Using data from Mississippi and Maryland, we determined that educational attainment of women giving birth is a feasible substitute for census data in estimating the low-income maternity population, and that vital statistics data offer several advantages for estimating the maternity services target population over census data.
In connection with developing a benefit-cost approach to evaluating proposed rehabilitation research or demonstration projects, the need to estimate the numerical size of the associated target population is explained and a process is described for making such estimates. The process consists of 7 steps: (1) delineating project objectives, (2) specifying target group(s) in operational terms, (3) determining whether satisfactory target population prevalence estimates are available, (4) in the absence of such estimates, identifying a critical parent population and establishing its prevalence, (5) identifying an accessible population, (6) enumerating the number and proportion of target group members in the accessible population, (7) calculating the estimated target population by multiplying data yielded in steps (4) and (6), adjusting for inferred biases and indicating uncertainties of estimation. Consideration is given to the kinds of data bases upon which this estimation process depends, to the feasibility of providing such estimates, and to their probable accuracy.
The performance of tests for the detection of antibodies to Aujeszky's disease virus glycoprotein E (gE) in a target population was evaluated by constructing and analysing receiver operating characteristic (ROC) curves. These curves assess the discriminating ability of a test over the entire range of test signals. The advantages of applying the analysis to a sample of the target population (all commercial pigs in the Netherlands), as compared to using a panel of test sera, are that the estimates of sensitivity and specificity, the comparisons between tests and the choices of the cut-off values are all relevant for the target population. The results of a gE-ELISA in colostrum (test A) and in a single droplet of whole blood (test B) were compared with the results obtained with the same ELISA in serum (gold standard). The area under the ROC curve, which is a quantitative measure of test performance, was significantly (P < 0.01) smaller with test A than test B or the gold standard, indicating that test B performed better than test A. No significant difference was observed between test B and the gold standard.
Nurses contribute to the social support field primarily through study of clinical and community populations. A review of the target populations identified in 63 empirical studies of social support conducted in the past decade revealed that nurses have, to date, studied populations central to their profession's activities and concerns. They have uniquely focused on surgical patients, the chronically ill, expectant couples and parents of infants, the bereaved, and lay caregivers. These target groups have suffered from maturational (transitional) and/or situational stressors. However, some at-risk groups have been overlooked; in particular, children, males only, native peoples, the poor, the unemployed, and the victims of child and elder abuse. Nurses practice in diverse institutional and community-based sites, and hence have direct contact with all these population groups. Once the features of a population that make it a fruitful focus of study by nurse investigators are identified, pertinent interventions can be tested.
Target populations for chemoprevention trials should include those at higher than average risk for the development of prostate cancer as defined by explicit epidemiologic and genetic criteria. Such populations include a "primary prevention" group without histologic or clinical evidence of cancer, and several clinical models of "secondary prevention," including those with clinically evident disease prior to definitive therapy and those at high risk of recurrence after therapy based on histological or biochemical status. Each risk group and clinical model has potential advantages and disadvantages, and the mechanisms that underlie disease development and progression in each group may be unique. These observations give rise to many potential clinical trials of specific agents. These trials should also include collection of data on potentially confounding influences on disease development and progression.
The study populations taking part in early clinical drug development of reproductive endocrine treatments are discussed. After having compared subjects in phase I studies with subsequent target populations, the question was posed as to whether the inclusion of the later target population could accelerate the developmental process. This applies only to certain specific clinical questions that are posed in phase I studies. From the authors' perspective, the key goal of rapid and well-structured early drug development is to be attained by using reliable surrogate markers that are able to reflect the clinical effects.
A review of tuberculosis surveillance data from a program of school-based tuberculin testing demonstrates the natural evolution of targeted populations. In the 7 years encompassed by this study, the prevalence of tuberculin reactivity ranged from 4.3% to 6.1% in the Amarillo public school populations which were tested. The initial screening was a sampling of all students in the school district. In subsequent years' screening, the targeted populations were increasingly refined to eliminate lower-risk populations. Children enrolled in "English as a Second Language" (ESL) classes were found to have an 8.5% tuberculosis infection rate. The purpose of this study was to alert nurses that culturally sensitive approaches are needed for successful future testing.
Scholars have devoted considerable attention to analyzing the social construction of AIDS. To explore the politics of AIDS policymaking, this research uses Schneider and Ingram's (1993) theory of the social construction of target populations to evaluate the U.S. Senate's response to AIDS between 1987 and 1992. Our study found that Schneider and Ingram's model provides important insights into how political processes affect AIDS policy design. While our data did not strictly conform to all of the model's theoretical expectations, the data provided evidence confirming its predictions about broad patterns in the allocation of both substantive and symbolic policy benefits and burdens to different target populations.
Our experience with studies investigating central nervous system active compounds in Alzheimer disease (AD) patients suggest that conducting a "bridging study," in which patients from the target population are included in Phase I, could expedite the drug development process in AD. With one acetylcholinesterase (AChE) inhibitor compound (velnacrine), we found that AD patients tolerated considerably lower dosages than young normals and healthy elderly subjects, whereas our findings were exactly the opposite with another AChE inhibitor (eptastigmine). In studies of a muscarinic agonist (CI-979), AD patients were able to tolerate dosages higher than those that were well tolerated in young normals. A possible explanation for differences in drug effect and tolerance in the target population may be the pathologic changes in both the brain and the peripheral nervous system that are associated with AD.
The efficacy of a drug is a quantitative concept rather than a qualitative one. This quantity is expressed by several efficacy indices. None of them meet all the requirements. However, that of absolute benefit is especially suitable for the patients because it tells them the exact gain they can expect from taking the treatment. The absolute benefit varies according to patients' profiles because it interacts with some components of these profiles. In theory, such interactions can be used to predict the size of the absolute benefit for each patient, as well to describe better than with the current tools the therapy target population. We explain why meta-analysis and effect models are means of improving the prediction of the size of the effect and the definition of the therapy target population.
We assessed the effect of two different methods of contacting the target population on the rate of participation in a colorectal cancer screening programme. All individuals aged between 50 and 74 years enlisted in one primary health care centre in Barcelona (Spain) were included in a prospective randomized controlled trial. An invitation letter signed by a doctor together with two containers for faecal sample collection were sent by post to subjects in the 'standard' group (n = 1060), while subjects in the 'study' group (direct contact, n = 965) were visited by a trained non-health professional who supplied them with the same documentation as the standard group. The screening test consisted of an immunological method for the detection of faecal blood which does not require any prior specific dietary measures. Specimens were collected on two successive days. A significantly higher participation was observed in the study group (557/965, 57.7%) compared with the standard group (388/1060, 36.5%, P < 0.005). Specimen collection correctness was also higher in the study group (419/557, 75.1%) compared with the standard group (262/388, 67.5%, P < 0.014). There were no differences in terms of either age group or sex for the participation, nor for degree of correctness of specimen collection. Participation and specimen collection can be raised in colorectal cancer screening programmes by means of an invitation made through direct contact by a suitably trained non-health professional.
Chemoprevention trials usually target healthy populations and employ non-toxic chemicals in an effort to eliminate, reduce, or reverse premalignant lesions or early cancer. Recent efforts have been directed at short-term Phase II trials which rely on changes in surrogate endpoint biomarkers rather than cancer incidence reduction as an endpoint. Chemopreventive agents are chosen that are likely to produce a modulating effect on one or more biomarkers in prostate cancer, including extent and grade of morphometric, genetic, proliferative, differentiative, and regulatory biomarkers. Five target populations appear to have the greatest promise in chemoprevention trials for prostate cancer: (1) Patients with high-grade prostatic intraepithelial neoplasia, a microscopic lesion which is the likely precursor of some prostate cancers; (2) patients with early cancer treated by watchful waiting; (3) patients with cancer waiting for prostatectomy; (4) men at high risk of developing prostate cancer; and (5) men from the general population (normal risk of prostate cancer).
The ability of two voluntary health agencies to provide suitable target populations for epidemiologic research was explored in a pilot study of epilepsy. The results suggest that, properly approached, voluntary agencies offer advantage for this purpose. In the first agency (Group A), subjects were recruited by mail, producing a response rate of 15%. In the second agency (Group B), subjects were recruited by telephone, producing a response rate of 87%. A structured, precoded telephone interview about personal and family history of seizure disorders was administered to both groups of subjects. Subjects in Group A gave permission to contact a higher proportion of their eligible relatives than did those in Group B (73 vs 57%). Permission was obtained more often for relatives reported to have had seizures (Group A 86%, Group B 78%) than for other relatives. 89% of relatives contacted directly agreed to be interviewed. Consent forms for medical record review were signed and returned by 95% of Group A and 77% of Group B subjects. Diagnoses of etiology and seizure type of epilepsy based on the interview data agreed with diagnosis based on the medical records in most cases. In first-degree relatives of subjects with epilepsy, reported rates of epilepsy did not appear to be seriously biased.
Two experiments were carried out to identify the target population of cattle for immunisation against East Coast fever (ECF) using the infection-and-treatment method. Firstly, a sentinel-calf study was used to determine the age window for ECF immunisation by determining ages at clinical detection of infection with Theileria parva. Six groups of five naive cross-bred (Bos taurus/Bos indicus) male calves, introduced at intervals of 2 months at a mean age of 26 days, were exposed to natural tick challenge on a high ECF-risk, small-holder farm in the coastal lowland, coconut-cassava agro-ecological zone of coastal Kenya. Secondly, a challenge study evaluated the relationship between the presence of T. parva antibodies and immunity. Ten indigenous adult Zebu cattle and nine Zebu young stock purchased from farmers in the same zone, and eight cross-bred calves (survivors of the sentinel-calf study) were challenged with 10 times the immunising dose of T. parva Marikebuni stock. Twenty-four of these 27 cattle had high antibody titres before challenge. Two cross-bred calves, obtained from an ECF-free area and seronegative to T. parva schizont antigen, also were challenged and used as susceptible controls. Twenty-five (83%) of the 30 sentinel calves contracted ECF over an age range of 36-116 days (mean 72 days). The remaining five calves died of other causes within 2 months of arrival on the farm. Fourteen of the 25 calves survived the infection and developed antibodies to T. parva. Despite tick control, seven of these 14 calves had a second episode of ECF and two died. In total, 13 of the 25 calves that contracted ECF died. Only one of 19 indigenous Zebu animals developed clinical ECF when challenged with T. parva Marikebuni (mild clinical signs with spontaneous recovery). Of the eight cross-bred survivors from the first experiment, only one succumbed to ECF when challenged and it died. Both susceptible cross-bred calves developed severe clinical signs of ECF and one died. The experimental studies show that in the high ECF-risk areas of the coconut-cassava zone of coastal Kenya, immunisation against ECF in cross-bred (B. taurus/B. indicus) cattle should be targeted at an early age (preferably within 1-2 months of birth).
The purpose of this document is to provide recommendations for the selection of the optimal target population for lung cancer screening trials with Spiral Computer Tomography based on an analysis of risk factors and high-risk populations. Our recommendations are to include current or ex-smokers (<5 years) with a smoking history of at least 30 years and an average consumption of at least 20 cigarettes a day. When these selection criteria are applied there is no need for a lower age cut-off. Elderly people can be included as long as their life expectancy is more than 10 years. Participants should be fit enough to undergo thoracic surgery. They may have a history of previous cancer, provided that the cancer has been curatively treated at least 5 years ago without evidence of relapse, except for breast cancer, melanoma and hypernephroma. People with an inability to lie flat, who are unable to hold their breath for 20 s, with a body weight above 140 kg, a chest CT scan within 1 year before enrolment or a previous pneumonectomy should not be invited. The inadequacy of the unit 'Pack-Years' (PY) to estimate the individual lung cancer risk is recognised, and future initiatives to develop an appropriate lung cancer risk model are encouraged.