Identifying heterogeneity among injection drug users: a cluster analysis approach

Objectives. We used cluster analysis to subdivide a population of injection drug users and identify previously unknown behavioral heterogeneity within that population.Methods. We applied cluster analysis techniques to data collected in a cross-sectional survey of injection drug users in Winnipeg, Manitoba. The clustering variables we used were based on receptive syringe sharing, ethnicity, and types of drugs injected.Results. Seven clusters were identified for both male and female injection drug users. Some relationships previously revealed in our study setting, such as the known relationship between Talwin (pentazocine) and Ritalin (methylphenidate) use, injection in hotels, and hepatitis C virus prevalence, were confirmed through our cluster analysis approach. Also, relationships between drug use and infection risk not previously observed in our study setting were identified, an example being a cluster of female crystal methamphetamine users who exhibited high-risk behaviors but an absence or low prevalence of blood-borne pathogens.Conclusions. Cluster analysis was useful in both confirming relationships previously identified and identifying new ones relevant to public health research and interventions.Syringe sharing is a well-established mechanism for the spread of HIV and HCV.1^–3 The introduction of syringe exchange programs (SEPs) has had a substantial impact with respect to decreasing the attributable risk of infectious blood-borne pathogens such as HIV and HCV among injection drug users.4^–11 However, studies have shown variations in the effectiveness of SEPs,11^–18 in that syringe sharing behavior persists among some injection drug users.12^,18^–21Epidemiological studies in which contextual factors are used to explain syringe sharing (i.e., social network analyses22) have demonstrated that sharing behavior is not based exclusively on individual choice7^,23^–26; that is, factors other than syringe access may drive sharing among certain injection drug users.20^,26^–28 For example, syringe sharing has been demonstrated to be associated with dyadic relationships involving close friends or sexual partners12^,26^,29^,30 and partnerships in which injection drug users pool resources to obtain drugs or injection equipment.21^,24^,26^,31^,32 Thus, variation in sharing behaviors is explained by differences between high-risk groups.Some researchers suggest that designing interventions around variances seen between groups, and the context in which these variances reside, may be both efficient and efficacious,33^–38 especially in terms of public health practice. Understanding the heterogeneity in high-risk groups may be particularly relevant for those behaviors that persist despite the establishment of structural interventions such as SEPs.15^,18^–20^,28^,39^–44 Consequently, the use of nontraditional statistical methodologies (such as social network analysis) has been encouraged to capture this variance.33^,35 Cluster analysis,45^,46 “an exploratory technique that can be used to reveal unknown heterogeneity,”35^(p196) focuses on the inherent differences between cases rather than variables. It has been used in the HIV literature to develop typologies of behavior33^,37; however, its use is more widespread in the psychiatric and psychological literatures.38^,47^–50We used cluster analysis as an exploratory tool to investigate whether empirically derived clusters could help to explain heterogeneity in a sample of injection drug users. The broader applicability of this technique to public health investigations in general was also addressed.     

系统聚类法与综合指数法在临床科室评先中的应用

目的找到一种使医院不同业务性质临床科室能够进行评比的标准尺度。方法采用系统聚类法与综合指数法相结合的评价方法,用系统聚类法将临床科室依据工作指标进行分类,再用综合指数法在每一类临床科室中选出最优科室。结果实现了依据多数量指标聚类选最优临床科室。结论通过系统聚类法与综合指数法的结合,实现医院不同性质临床科室之间的评比,克服了主观人为因素的影响,为医院激励优秀科室提供了参考方法。     

海南居民对高温天气健康风险的感知

  目的  探讨海南省居民在高温天气中不良症状的特点及影响其出现不良症状后未就诊的因素。  方法  采用2013年在海南省收集的关于“海南省居民高温天气下健康风险感知与适应研究”的数据,对居民在高温条件下不良症状的反应进行描述并采用单因素卡方检验及多因素logistic回归方法分析影响出现不良症状后未就诊的因素。  结果  高温条件下慢性病者出现主要不良症状为烦躁,比例为30.20 %;非慢性病患者出现主要不良症状也为烦躁,比例为35.20 %;高温条件下,出现胸闷症状在是否患在有慢性病人群中的差异有统计学意义（P < 0.05）;人群出现不良症状未就诊率为77 %;影响因素中健康风险感知高（OR = 0.43,95 % CI = 0.32～0.58）、经常进行健康宣传（OR = 0.46,95 % CI = 0.31～0.67）、年龄 ≥ 60岁（OR = 0.63,95 % CI = 0.38～0.94）就诊可能性大,而自我感觉身体健康（OR = 2.55,95 % CI = 1.49～4.35）未就诊可能性较大。  结论  高温条件下人群出现主要不良症状为烦躁,其中缺乏健康教育,不能正确认识自身健康状况等是影响居民在高温条件下出现不良症状不能及时就诊的主要因素。     

Is daily single dosage of diazepam as effective as chlordiazepoxide in divided doses in alcohol withdrawal--a pilot study

We report on a pilot double-blind study on the effectivenessof divided doses of chlordiazepoxide and a single daily doseof diazepam in the treatment of the alcohol-withdrawal syndrome.While a variety of drugs (chlormethiazole, propranolol and clonidine)have been used for treatment of alcohol-withdrawal symptoms,benzodiazepines remain the drugs of choice for alcohol detoxification(Mayo-Smith, 1997). Diazepam and chlordiazepoxide are both . . . [Full Text of this Article]APPENDIXFOOTNOTESREFERENCES     

Investigation of a testicular cancer cluster using a case-control approach

A case-control methodology was developed and utilized to investigate a reported cluster of testicular cancer among leather workers in New York. Eighteen cases of testicular cancer, including the three index cases, diagnosed from 1974 to 1986 among residents of two counties with substantial leather tanning and finishing establishments made up the case group. Controls (n = 259) consisted of men of similar age who had been diagnosed with cancers of all other sites during the same time period. Reports of usual occupation for cases and controls, obtained from cancer registry reports and death certificates, indicated that cases were much more likely to be leather workers (28%) than controls (7%). After adjustment for age, the relative risk estimate for occupation and testicular cancer was 7.2 (95% Cl: 1.9-27.7). The association was further supported by occupational histories showing similar work environments within the leather industry for five out of six cases known to have been leather workers. Case-control analysis of a reported cluster does not provide independent confirmation of an association between occupational factors and testicular cancer. The methodology, however, can provide a timely way to evaluate the significance of occupational cancer clusters.     

Neurobiology and treatment in alcoholism--recent findings regarding Lesch's typology of alcohol dependence

Subtyping in alcohol dependence has become an important issue as studies have proposed different neurobiological mechanisms in alcoholism in the recent years. Studies have shown that alcohol dependence reflects a wide range of different phenotypes, including psychological, social, and neurobiological factors. Different ways of subtyping have been proposed in the last decades, one of them being Lesch's typology of alcohol dependence. Recent investigations have shown that different subtypes of Lesch's typology are associated with specific neurobiological factors which may have important implications for clinical practice. This applies in particular for genetic and neuroendocrinological factors, differences in the regulation of NMDA receptor-mediated glutamatergic neurotransmission, and in response to acamprosate and naltrexone treatment.     

Teaching primary health care: a comprehensive approach

The MEDEX Primary Health Care Series, an integrated training system for everyone in primary care (PHC), was published in 1983. It is now used in over 70 countries and has demonstrated its value in the developing world. The Series lays considerable emphasis on the crucial link between the performance of health workers and the management support with which they are provided. It was the result of 10 years of development and field testing. The Series is so widely employed because its development involved health centers and health workers associated in PHC programs in Guyana, Lesotho, Micronesia, Pakistan, and Thailand. It also addresses everyday problems and provides pragmatic solutions which PHC programs can apply. Attention is given to the development of skills in health workers, using a competency-based methodology, in contrast to the concentration on knowledge acquition found in more conventional training programs. Training activities are detailed for as little as 15 minutes at a time in courses lasting 6-15 months. Dialogic methods are used for the more peripheral workers who may not be literate. Management is given systematic, practical treatment. The Series advocates disease prevention and health promotion and helps to train health workers to diagnose an treat the most common clinical problems. It can be used to strengthen existing programs or to start new ones. It has a consistent formant, facilitating local adaption. Any part of the Series can be copied or reproduced for noncommercial purposes without persmission from the publisher. The Series is based on the realistic and pragmatic organization of health care delivery systems found in most countries and places great importance on the use of health center presonnel to orientate and link resources at the center to needs at the periphery. Nurses, the health center person at the middle level of the PHC, often fulfills the role of trainer and supervisor of the community health worker. The diagnostic, curative and community health skills in the Series are consistent with the expanding role of nursing in PHC. The Series is published in English but also available in a mini-edition in Spanish with increasing interest in a French translation. Various sections have been translated into 21 other languages. A newsletter and a network of series users (MEDINET) has been established.     

A regression approach to the analysis of data arising from cluster randomization

A generalized least squares regression approach is proposed for the analysis of data arising from experimental studies involving cluster randomization and non-experimental studies in which the major treatment factor corresponds to a characteristic which applies at the cluster level. This approach is more flexible than that provided by the analysis of variance, and unlike ordinary least squares, provides significance levels which are adjusted for the correlation among elements within the same cluster. Two examples are presented.     

Stratified analysis of multivariate clinical data: application of a Mantel-Haenszel approach

Laboratory determinations on children aged 6 to 10 years obtained over a 5-year period are analysed by a method described in detail for differentiating between children from exposed and control areas of Seveso, Italy. In the analysis, stratification is employed to distinguish the separate days of laboratory measurement. The analyses permit the study of differences based on all variables simultaneously as well as on each variable separately. Results are obtained for each individual year and for longer intervals of 2 successive years, 3 successive years, 4 successive years, and all 5 years. The results and some statistical aspects of the analysis are discussed.     

The numerical approach to classification: a medical application to develop a typology for facial pain

Applications of numerical taxonomy in medicine are relatively rare. We describe an application in which a new typology is developed for the classification of pain distribution in patients with temporomandibular pain dysfunction syndrome. The methodology of the numerical approach is presented and key issues are highlighted, especially relating to validation of taxonomic structure. From the dendrogram obtained by Ward's hierarchical method, five pain groups are distinguished which relate systematically to anatomy and are clinically meaningful. Cluster structure is subjected to a battery of reproducibility tests and is found to be broadly reproducible for different algorithms and sub-samples of subjects. Finally, the new typology is shown to have heuristic value in providing fresh insight into the nature of a complex syndrome.     

Student assessment in community settings: a comprehensive approach

Student assessment in community settings presents problems for medical teachers, e.g. difficulties in assessing the contribution of individual members to group work, and lack of test standardization due to varying field conditions. The Faculty of Medicine, University of Gezira, Sudan is a community-oriented, community-based medical school which has adopted a comprehensive approach to student assessment in community settings using various methods, including peer assessment, a supervisory checklist, community feedback, reports from students, short essay questions (SEQs) and multiple choice questions (MCQs). Each method focuses on a specific aspect of the objectives of the community-based programme and is weighted in the final grade according to the extent to which objectives were covered. This assessment programme contrasts with the conventional teacher-centred approach, and is continuously monitored and improved using a variety of sources of information. A total of 105 students participated in a study designed to measure the reliability and validity of this approach. The reliability of the methods was tested by computing the alpha coefficient and was found to range between 0·77 and 0·92. This was considered acceptable. The validity of the instruments was examined using confirmatory factor analysis, and their content validity was reviewed. The results show that the comprehensive approach used is fairly valid. It is suggested that the University's approach is successful in solving some of the problems of student assessment in community settings.     

Some extensions to a new approach for interim analysis in clinical trials

There already exists many methods for group sequential analysis of clinical trials. A new approach suggests to preserve the overall type I error alpha by requiring that a succession of interim analyses be significant at the alpha level. In this paper, this procedure is extended. A rule for early acceptance of H0 is presented, with an extension for flexible number and times of analyses. A real example is given.     

Identifying determinants of protocol adoption by midwives: a comprehensive approach

Adoption of potentially effective preventive interventions often fails. This study aimed to identify factors that determine why midwifery practices decide to use a smoking cessation protocol, using a comprehensive model of both organizational and psychosocial factors. A cross-sectional survey was conducted among representatives of all 446 Dutch midwifery practices, of whom 251 (56%) responded. The results show that adoption of the protocol was facilitated by the presence of practice assistants and impeded by a large proportion of clients of foreign ethnic origin. The most successful information channel was the midwives' professional association. A consistent positive attitude (perceiving a lot of advantages, few disadvantages and a low level of ambivalence) and positive social norms toward using the protocol, a perceived large proportion of midwives who use the protocol and knowledge about the protocol significantly increased the likelihood of adoption. The decision to use the protocol was better explained by personal awareness and motivation factors than by organizational factors.     

Experiencing the postpartum period: a comprehensive approach of social phenomenology

The aim of this study was to achieve an understanding of what new mothers served by private health care realize about the postpartum period, as well as identifying what their help and care needs are, during this life cycle. The research development proposition has been grounded on a qualitative research model with the phenomenological approach. Some categories came out from the statements: Taking charge of her child; feeling overloaded, overwhelmed and insecure; sensing herself vulnerable; experiencing a magic and unique emotion; reporting postpartum care satisfaction. After reviewing the categorical analysis, the postpartum living experiences as described by the subjects have been found quite similar to that of women without private health care. Nevertheless, the access to good quality in private health services became an important aspect because it enabled a close subjective relationship of mother and health care professional, allowing a safe postpartum experience.