Pub Date : 2001-01-01DOI: 10.1080/135952201317225480
R. Giorgi, G. Hédelin, P. Schaffer
BACKGROUND Relative survival is a method of analysis of failure-time data used to estimate the net survival. Cancer registries frequently use this method. The main regressive models are the Hakulinen and Tenkanen model, and the Esteve et al. model, which are easily used in practice thanks to their specific software (SURV and RELSURV, respectively). An assessment of the behaviour of the models is made, with the aim of giving advice for users of lifetime data in practice. METHODS Simulations were done by respecting, then violating, the basic hypothesis supporting the theoretical foundation of these two proportional hazard models (independence of the death and censor process, proportionality of risks). For each simulation, 100 files of either 100, 1,000, or 10,000 individuals were generated to assess the behaviour of the model. RESULTS Moderate censor rates, with or without proportionality assumption, lead to the use of the Hakulinen and Tenkanen model, especially for studies with little information. Non-proportionality of risks in the Hakulinen and Tenkanen model could be tested and analysed. If assumptions underlying the models are respected, the Esteve et al. model seems to be more precise. DISCUSSION The choice of a model in practice depends on its performance, and on the user's knowledge of statistics and computer science. Non-proportionality of risks is common in cancer registries. In theory, non-proportionality of risks could be taken into account for both relative survival models but, for the moment, it is feasible in routine only for the Hakulinen and Tenkanen model. Characteristics of the software should also be taken into account for routine relative survival analyses.
{"title":"Relative survival: comparison of regressive models and advice for the user.","authors":"R. Giorgi, G. Hédelin, P. Schaffer","doi":"10.1080/135952201317225480","DOIUrl":"https://doi.org/10.1080/135952201317225480","url":null,"abstract":"BACKGROUND Relative survival is a method of analysis of failure-time data used to estimate the net survival. Cancer registries frequently use this method. The main regressive models are the Hakulinen and Tenkanen model, and the Esteve et al. model, which are easily used in practice thanks to their specific software (SURV and RELSURV, respectively). An assessment of the behaviour of the models is made, with the aim of giving advice for users of lifetime data in practice. METHODS Simulations were done by respecting, then violating, the basic hypothesis supporting the theoretical foundation of these two proportional hazard models (independence of the death and censor process, proportionality of risks). For each simulation, 100 files of either 100, 1,000, or 10,000 individuals were generated to assess the behaviour of the model. RESULTS Moderate censor rates, with or without proportionality assumption, lead to the use of the Hakulinen and Tenkanen model, especially for studies with little information. Non-proportionality of risks in the Hakulinen and Tenkanen model could be tested and analysed. If assumptions underlying the models are respected, the Esteve et al. model seems to be more precise. DISCUSSION The choice of a model in practice depends on its performance, and on the user's knowledge of statistics and computer science. Non-proportionality of risks is common in cancer registries. In theory, non-proportionality of risks could be taken into account for both relative survival models but, for the moment, it is feasible in routine only for the Hakulinen and Tenkanen model. Characteristics of the software should also be taken into account for routine relative survival analyses.","PeriodicalId":80024,"journal":{"name":"Journal of epidemiology and biostatistics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59835718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-01-01DOI: 10.1080/135952201753173015
E. Couto, D. Harrison, S. Duffy, J. Myles, E. Sala, R. Warren, N. Day, R. Luben, H. Chen
BACKGROUND Estimations of mean sojourn time (MST) and sensitivity (S) in disease screening have been previously calculated from case-control data, using simple models which did not include covariates. Many studies have shown an effect of mammographic parenchymal pattern (MPP) on breast-cancer risk and tumour histology. We have expanded previous models on these to estimate MST and S with the effects of MPP as a covariate. METHODS Data were from a nested case-control study within the East Anglian screening programme, with 875 cases and 2,601 controls. Estimates of disease progression and screening parameters were based on conditional likelihood calculation, using a Markov process model. Ninety-five per cent confidence intervals (CI) were calculated using the profile likelihood wherever possible and using a numerical estimate of the information matrix or the area under the likelihood curve where necessary. RESULTS We obtained estimates of the incidence of preclinical disease, rate of transition from preclinical to clinical and screening sensitivity, and evaluated the association of these parameters with mammographic parenchymal pattern. A higher incidence of preclinical disease was found for high-risk MPP [relative incidence = 1.62 (95% CI: 0.89; 2.73)]. However, no difference in progression rate from preclinical to clinical disease between different MPP was found. Dense MPPs were associated with decreased sensitivity [relative sensitivity = 0.24 (95% CI: 0.06; 15)]. Wide CIs were found, probably being a consequence of the relative sparsity of interval cancer data. DISCUSSION It is possible to estimate multiple parameters of disease progression and screening quality from case-control data. The reduction in sensitivity of the screening process associated with high-risk patterns presented here, could be of paramount interest for proposing new screening strategies, such as possible additional screening tools.
{"title":"Estimation of disease progression parameters from case-control data: application to mammographic patterns and breast cancer natural history.","authors":"E. Couto, D. Harrison, S. Duffy, J. Myles, E. Sala, R. Warren, N. Day, R. Luben, H. Chen","doi":"10.1080/135952201753173015","DOIUrl":"https://doi.org/10.1080/135952201753173015","url":null,"abstract":"BACKGROUND Estimations of mean sojourn time (MST) and sensitivity (S) in disease screening have been previously calculated from case-control data, using simple models which did not include covariates. Many studies have shown an effect of mammographic parenchymal pattern (MPP) on breast-cancer risk and tumour histology. We have expanded previous models on these to estimate MST and S with the effects of MPP as a covariate. METHODS Data were from a nested case-control study within the East Anglian screening programme, with 875 cases and 2,601 controls. Estimates of disease progression and screening parameters were based on conditional likelihood calculation, using a Markov process model. Ninety-five per cent confidence intervals (CI) were calculated using the profile likelihood wherever possible and using a numerical estimate of the information matrix or the area under the likelihood curve where necessary. RESULTS We obtained estimates of the incidence of preclinical disease, rate of transition from preclinical to clinical and screening sensitivity, and evaluated the association of these parameters with mammographic parenchymal pattern. A higher incidence of preclinical disease was found for high-risk MPP [relative incidence = 1.62 (95% CI: 0.89; 2.73)]. However, no difference in progression rate from preclinical to clinical disease between different MPP was found. Dense MPPs were associated with decreased sensitivity [relative sensitivity = 0.24 (95% CI: 0.06; 15)]. Wide CIs were found, probably being a consequence of the relative sparsity of interval cancer data. DISCUSSION It is possible to estimate multiple parameters of disease progression and screening quality from case-control data. The reduction in sensitivity of the screening process associated with high-risk patterns presented here, could be of paramount interest for proposing new screening strategies, such as possible additional screening tools.","PeriodicalId":80024,"journal":{"name":"Journal of epidemiology and biostatistics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59836655","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-01-01DOI: 10.1080/135952201753337149
N. Schlecht, E. Franco, T. Rohan, S. Kjaer, M. Schiffman, A. Moscicki, S. Duffy
BACKGROUND Misclassification of sexual history due to faulty recall or reporting bias may be the reason for variability in the association between sexual history and human papillomavirus (HPV) infection seen in studies conducted in different geographical areas. This study aimed to assess the repeatability of questionnaire information on sexual-history variables and their correlates, using information from repeat interviews by six international prospective cohort studies. METHODS The pooled dataset included over 14 775 women interviewed on two separate occasions, of whom 5690 returned for a third interview. At each return visit women were re-asked questions on age at first intercourse and number of sexual partners. The six cohorts originated from studies in Denmark, Costa Rica. San Francisco, Toronto, Montreal and São Paulo. RESULTS Exact agreement between age at first intercourse recalled on separate occasions ranged from 60-85%, whereas exact recall rates for number of sexual partners were substantially lower and more study-dependent, varying between 20% and 77%. The intraclass correlation coefficients gauging the degree of repeatability in responses ranged from 0.68 to 0.97 for age at first intercourse and 0.08 to 0.94 for number of sexual partners. Age, ethnicity, education and cohort membership were the strongest predictors of reporting error for both sexual history markers, although study design characteristics also seemed to play a role. HPV infection status seemed to influence recall of number of partners, but not age at first intercourse. CONCLUSIONS Information on sexual behaviours is not reliably collected in epidemiological studies of sexually transmitted diseases, which may influence the magnitude of relative risk estimates.
{"title":"Repeatability of sexual history in longitudinal studies on HPV infection and cervical neoplasia: determinants of reporting error at follow-up interviews.","authors":"N. Schlecht, E. Franco, T. Rohan, S. Kjaer, M. Schiffman, A. Moscicki, S. Duffy","doi":"10.1080/135952201753337149","DOIUrl":"https://doi.org/10.1080/135952201753337149","url":null,"abstract":"BACKGROUND Misclassification of sexual history due to faulty recall or reporting bias may be the reason for variability in the association between sexual history and human papillomavirus (HPV) infection seen in studies conducted in different geographical areas. This study aimed to assess the repeatability of questionnaire information on sexual-history variables and their correlates, using information from repeat interviews by six international prospective cohort studies. METHODS The pooled dataset included over 14 775 women interviewed on two separate occasions, of whom 5690 returned for a third interview. At each return visit women were re-asked questions on age at first intercourse and number of sexual partners. The six cohorts originated from studies in Denmark, Costa Rica. San Francisco, Toronto, Montreal and São Paulo. RESULTS Exact agreement between age at first intercourse recalled on separate occasions ranged from 60-85%, whereas exact recall rates for number of sexual partners were substantially lower and more study-dependent, varying between 20% and 77%. The intraclass correlation coefficients gauging the degree of repeatability in responses ranged from 0.68 to 0.97 for age at first intercourse and 0.08 to 0.94 for number of sexual partners. Age, ethnicity, education and cohort membership were the strongest predictors of reporting error for both sexual history markers, although study design characteristics also seemed to play a role. HPV infection status seemed to influence recall of number of partners, but not age at first intercourse. CONCLUSIONS Information on sexual behaviours is not reliably collected in epidemiological studies of sexually transmitted diseases, which may influence the magnitude of relative risk estimates.","PeriodicalId":80024,"journal":{"name":"Journal of epidemiology and biostatistics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59837102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-01-01DOI: 10.1080/135952201317225435
J. Martin-Moreno
{"title":"The rating of public health research: a complex but necessary exercise.","authors":"J. Martin-Moreno","doi":"10.1080/135952201317225435","DOIUrl":"https://doi.org/10.1080/135952201317225435","url":null,"abstract":"","PeriodicalId":80024,"journal":{"name":"Journal of epidemiology and biostatistics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59835634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-01-01DOI: 10.1080/13595220152601828
L. Sharples, G. I. Taylor, M. Faddy
BACKGROUND Markov and semi-Markov models are increasingly used in clinical and public health epidemiology to represent disease processes. We present a Markov model of events following lung transplantation as a case study in clinical epidemiology. METHODS A five-state discrete-time Markov model with two-way transitions between acute event states is applied to the analysis of 356 lung transplant patients. A two-state continuous time Markov model for chronic disease onset is fitted. Values of transition parameters are estimated by maximum likelihood using numerical methods. RESULTS Accurate estimates of acute and chonic event rates, and survival probabilities are calculated from transition probabilities. Costs attributed to different acute and chronic states are calculated. CONCLUSIONS Transition models provide a useful and flexible representation of acute and chronic events and can be used to explore the economic impact of changes in therapy.
{"title":"A piecewise-homogeneous Markov chain process of lung transplantation.","authors":"L. Sharples, G. I. Taylor, M. Faddy","doi":"10.1080/13595220152601828","DOIUrl":"https://doi.org/10.1080/13595220152601828","url":null,"abstract":"BACKGROUND Markov and semi-Markov models are increasingly used in clinical and public health epidemiology to represent disease processes. We present a Markov model of events following lung transplantation as a case study in clinical epidemiology. METHODS A five-state discrete-time Markov model with two-way transitions between acute event states is applied to the analysis of 356 lung transplant patients. A two-state continuous time Markov model for chronic disease onset is fitted. Values of transition parameters are estimated by maximum likelihood using numerical methods. RESULTS Accurate estimates of acute and chonic event rates, and survival probabilities are calculated from transition probabilities. Costs attributed to different acute and chronic states are calculated. CONCLUSIONS Transition models provide a useful and flexible representation of acute and chronic events and can be used to explore the economic impact of changes in therapy.","PeriodicalId":80024,"journal":{"name":"Journal of epidemiology and biostatistics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59836117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-01-01DOI: 10.1080/135952201753172953
S. Senn
P-values are a practical success but a critical failure. Scientists the world over use them, but scarcely a statistician can be found to defend them. Bayesians in particular find them ridiculous, but even the modern frequentist has little time for them. In this essay, I consider what, if anything, might be said in their favour.
{"title":"Two cheers for P-values?","authors":"S. Senn","doi":"10.1080/135952201753172953","DOIUrl":"https://doi.org/10.1080/135952201753172953","url":null,"abstract":"P-values are a practical success but a critical failure. Scientists the world over use them, but scarcely a statistician can be found to defend them. Bayesians in particular find them ridiculous, but even the modern frequentist has little time for them. In this essay, I consider what, if anything, might be said in their favour.","PeriodicalId":80024,"journal":{"name":"Journal of epidemiology and biostatistics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59836209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-01-01DOI: 10.1080/135952201317225499
M. Kanariou, E. Petridou, E. Vrachnou, D. Trichopoulos
BACKGROUND It has been suggested that prolonged exposure to sunlight may induce systemic or local immune alterations, which may facilitate the development of skin cancer and, perhaps, non-Hodgkin's lymphona. The effects of prolonged sunlight exposure on peripheral blood cells were studied. METHODS Leukocytes and lymphocyte subpopulations of 12 volunteers aged 10-45 were investigated before and after a 3-week summer holiday in seaside resorts in Greece. Lymphocyte phenotypes were estimated using monoclonal antibodies and flow cytometry. RESULTS There were no significant differences with respect to total numbers of T cells, T-helper/inducer, T-suppressor/cytotoxic, B cells or HLA-Dr+ cells. However, we have found evidence of lymphocyte stimulation, reflected in an increase in cells expressing the interleukin-2 receptor (IL-2R) and, more specifically, an increase in the T cells expressing IL-2R and HLA-Dr antigens. An increase in natural killer cells has also been noticed. CONCLUSIONS These findings suggest that prolonged intense exposure to sunlight may be associated with immunostimulation, rather than immunosuppression.
{"title":"Lymphocyte alterations after prolonged sunlight exposure.","authors":"M. Kanariou, E. Petridou, E. Vrachnou, D. Trichopoulos","doi":"10.1080/135952201317225499","DOIUrl":"https://doi.org/10.1080/135952201317225499","url":null,"abstract":"BACKGROUND It has been suggested that prolonged exposure to sunlight may induce systemic or local immune alterations, which may facilitate the development of skin cancer and, perhaps, non-Hodgkin's lymphona. The effects of prolonged sunlight exposure on peripheral blood cells were studied. METHODS Leukocytes and lymphocyte subpopulations of 12 volunteers aged 10-45 were investigated before and after a 3-week summer holiday in seaside resorts in Greece. Lymphocyte phenotypes were estimated using monoclonal antibodies and flow cytometry. RESULTS There were no significant differences with respect to total numbers of T cells, T-helper/inducer, T-suppressor/cytotoxic, B cells or HLA-Dr+ cells. However, we have found evidence of lymphocyte stimulation, reflected in an increase in cells expressing the interleukin-2 receptor (IL-2R) and, more specifically, an increase in the T cells expressing IL-2R and HLA-Dr antigens. An increase in natural killer cells has also been noticed. CONCLUSIONS These findings suggest that prolonged intense exposure to sunlight may be associated with immunostimulation, rather than immunosuppression.","PeriodicalId":80024,"journal":{"name":"Journal of epidemiology and biostatistics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59835723","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-01-01DOI: 10.1080/135952201317080715
G. Kodraliu, P. Mosconi, N. Groth, G. Carmosino, A. Perilli, Gianicolo Ea, C. Rossi, Giovanni Apolone
BACKGROUND SF-12 is a generic short form health survey, developed in the USA from the original SF-36. It produces two summary measures evaluating physical and mental self-perceived health that are interchangeable with those from the SF-36. SF-12 has been successfully tested in nine Western European countries on large samples of the general population, where it has proved its brevity, comprehensiveness, reliability, validity and cross-cultural applicability. The present analysis directly assesses the SF-12 for the first time in various Italian settings, including the general population and specific patient groups. METHODS Data for this report were collected from five different samples; in four of them the SF-12 was used as a 'stand-alone' instrument, while in the other one (used as the reference) it was embedded in the SF-36. Descriptive statistics, Spearman's correlation coefficients, confirmatory factor analysis, ordinal uni- and multi-variate least squares regression model and covariance analysis were used to evaluate the summary measures in each sample, and across relevant subgroups. Studies were ordered according to the expected deviance, from the 'normal' health status of the reference group to the sample with the expected highest level of illness. RESULTS Overall, more than 11,000 subjects were evaluated. Response rates ranged from 63 to 100%, while missing items accounted only for 0.2-8.2% of all items. Uni- and multi-variate analyses showed a positive association between both physical component summary (PCS) and mental component summary (MCS) scores and their respective items in all examined samples. MCS scores were fairly similar across all samples, with the only exception being patients recently discharged from hospital, whose subjective mental health perception was higher than expected and the highest of all (52.2). Finally, we found a substantial impact of ageing on physical health perception, while the MCS was shown to be less sensitive to the age effect. CONCLUSIONS This analysis shows that the SF-12 has good validity, while some issues related to its most appropriate mode of administration and target groups might require further attention.
sf -12是在美国从原来的SF-36发展而来的一项通用的简短健康调查。它产生了两个评估身体和心理自我感知健康的总结措施，这些措施与SF-36中的可互换。SF-12已在9个西欧国家的普通人群中成功地进行了大样本测试，证明了它的简明性、全面性、可靠性、有效性和跨文化适用性。目前的分析首次在意大利的各种环境中直接评估了SF-12，包括一般人群和特定患者群体。方法本报告的数据来自5个不同的样本;其中四个SF-12被用作“独立”的仪器，而在另一个(用作参考)它被嵌入在SF-36中。采用描述性统计、Spearman相关系数、验证性因子分析、有序单变量和多变量最小二乘回归模型和协方差分析对每个样本和相关亚组的汇总测度进行评价。研究是根据预期偏差排序的，从参考组的“正常”健康状态到预期最高疾病水平的样本。结果总共评估了11,000多名受试者。应答率为63% ~ 100%，而缺失项目仅占所有项目的0.2 ~ 8.2%。单变量和多变量分析显示，在所有检测样本中，物理成分总结(PCS)和心理成分总结(MCS)得分及其各自的项目之间存在正相关。MCS得分在所有样本中都相当相似，唯一的例外是最近出院的患者，他们的主观心理健康感知高于预期，是所有样本中最高的(52.2)。最后，我们发现年龄对身体健康感知有实质性影响，而MCS对年龄影响不太敏感。结论本分析表明SF-12具有良好的效度，但其最合适的给药方式和目标人群等问题仍需进一步关注。
{"title":"Subjective health status assessment: evaluation of the Italian version of the SF-12 Health Survey. Results from the MiOS Project.","authors":"G. Kodraliu, P. Mosconi, N. Groth, G. Carmosino, A. Perilli, Gianicolo Ea, C. Rossi, Giovanni Apolone","doi":"10.1080/135952201317080715","DOIUrl":"https://doi.org/10.1080/135952201317080715","url":null,"abstract":"BACKGROUND SF-12 is a generic short form health survey, developed in the USA from the original SF-36. It produces two summary measures evaluating physical and mental self-perceived health that are interchangeable with those from the SF-36. SF-12 has been successfully tested in nine Western European countries on large samples of the general population, where it has proved its brevity, comprehensiveness, reliability, validity and cross-cultural applicability. The present analysis directly assesses the SF-12 for the first time in various Italian settings, including the general population and specific patient groups. METHODS Data for this report were collected from five different samples; in four of them the SF-12 was used as a 'stand-alone' instrument, while in the other one (used as the reference) it was embedded in the SF-36. Descriptive statistics, Spearman's correlation coefficients, confirmatory factor analysis, ordinal uni- and multi-variate least squares regression model and covariance analysis were used to evaluate the summary measures in each sample, and across relevant subgroups. Studies were ordered according to the expected deviance, from the 'normal' health status of the reference group to the sample with the expected highest level of illness. RESULTS Overall, more than 11,000 subjects were evaluated. Response rates ranged from 63 to 100%, while missing items accounted only for 0.2-8.2% of all items. Uni- and multi-variate analyses showed a positive association between both physical component summary (PCS) and mental component summary (MCS) scores and their respective items in all examined samples. MCS scores were fairly similar across all samples, with the only exception being patients recently discharged from hospital, whose subjective mental health perception was higher than expected and the highest of all (52.2). Finally, we found a substantial impact of ageing on physical health perception, while the MCS was shown to be less sensitive to the age effect. CONCLUSIONS This analysis shows that the SF-12 has good validity, while some issues related to its most appropriate mode of administration and target groups might require further attention.","PeriodicalId":80024,"journal":{"name":"Journal of epidemiology and biostatistics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59835463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-01-01DOI: 10.1080/13595220152601819
R. Marshall
BACKGROUND Case-control research is often exploratory; to determine factors that increase risk. Often, regression methods are used to determine combinations of risk factors that predispose to excess risk. Recently, tree-based methods have also been proposed. Both have limitations. An alternative approach is suggested, based on a search algorithm to identify at-risk subgroups. METHODS Statistical methods to determine and visualise at-risk sub-groups in case-control studies are presented. The method of determining sub-groups--search partition analysis (SPAN)--searches among different Boolean combinations of risk factors. Sub-groups that have been identified are visualised by scaled rectangle diagrams. These show the size of sub-groups and the extent to which they overlap. RESULTS Theory is presented for applying the method to case-control data. The methods are illustrated by analysis of three case-control studies: one on sudden infant death syndrome, a second on heart disease and a third on child pedestrian injuries. CONCLUSIONS The methods provide a useful alternative to regression and tree-based analysis. They demarcate subgroups that, in the three examples, are easy to interpret and would not have been found by other methods. Scaled rectangle diagrams are a useful way to visualise the results.
{"title":"Determining and visualising at-risk groups in case-control data.","authors":"R. Marshall","doi":"10.1080/13595220152601819","DOIUrl":"https://doi.org/10.1080/13595220152601819","url":null,"abstract":"BACKGROUND Case-control research is often exploratory; to determine factors that increase risk. Often, regression methods are used to determine combinations of risk factors that predispose to excess risk. Recently, tree-based methods have also been proposed. Both have limitations. An alternative approach is suggested, based on a search algorithm to identify at-risk subgroups. METHODS Statistical methods to determine and visualise at-risk sub-groups in case-control studies are presented. The method of determining sub-groups--search partition analysis (SPAN)--searches among different Boolean combinations of risk factors. Sub-groups that have been identified are visualised by scaled rectangle diagrams. These show the size of sub-groups and the extent to which they overlap. RESULTS Theory is presented for applying the method to case-control data. The methods are illustrated by analysis of three case-control studies: one on sudden infant death syndrome, a second on heart disease and a third on child pedestrian injuries. CONCLUSIONS The methods provide a useful alternative to regression and tree-based analysis. They demarcate subgroups that, in the three examples, are easy to interpret and would not have been found by other methods. Scaled rectangle diagrams are a useful way to visualise the results.","PeriodicalId":80024,"journal":{"name":"Journal of epidemiology and biostatistics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59836063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-01-01DOI: 10.1080/135952201753173006
W. Jędrychowski, U. Maugeri, I. Bianchi, E. Flak
BACKGROUND The main purpose of this study was to assess the effect of transient and continued asthma-like symptoms on lung function growth in preadolescent children. METHODS The follow-up respiratory health survey has been conducted on the sample of 1,129 children aged 9 years over 2 years follow-up. The basic health end-points were the occurrence of asthma-like symptoms and slower lung function growth (SLFG), which was defined as the lung function gain over 2 years within the lowest quintile of the distribution of a given spirometric test. RESULTS Adjusted odds ratios (OR) for SLFG [forced vital capacity (FVC)] were significantly higher only in the children having continued symptoms [OR = 3.39: 95% confidence interval (CI) = 1.39-8.27]. There was a consistent trend of adjusted ORs for SLFG [forced expiratory volume (FEV,) with the category of symptoms, where OR was 2.00 (95% Cl = 1.17-3.42) in children with transient symptoms: while 4.10 (95% Cl = 1.71-9.86) in children who had persistent symptoms. The corresponding ORs for SLFG [maximal mid-expiratory flow (FEF25_75c)] were 2.27 (95% Cl = 1.37-3.76); and 5.43 (95% Cl = 2.38-12.40). DISCUSSION The association between asthma-like symptoms and lung function gain in preadolescent children confirmed the clinical significance of the symptoms in question. The observed slower lung function gain in preadolescence may have implications for the development of chronic lung disease later in adulthood.
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