Greedy caliper propensity score matching can yield variable estimates of the treatment-outcome association-A simulation study.

PURPOSE: Greedy caliper propensity score (PS) matching is dependent on randomness, which can ultimately affect causal estimates. We sought to investigate the variation introduced by this randomness. METHODS: Based on a literature search to define the simulation parameters, we simulated 36 cohorts of different sizes, treatment prevalence, outcome prevalence, treatment-outcome-association. We performed 1:1 caliper and nearest neighbor (NN) caliper PS-matching and repeated this 1000 times in the same cohort, before calculating the treatment-outcome association. RESULTS: Repeating caliper and NN caliper matching in the same cohort yielded large variations in effect estimates, in all 36 scenarios, with both types of matching. The largest variation was found in smaller cohorts, where the odds ratio (OR) ranged from 0.53 to 10.00 (IQR of ORs: 1.11-1.67). The 95% confidence interval was not consistently overlapping a neutral association after repeating the matching with both algorithms. We confirmed these findings in a noninterventional example study. CONCLUSION: Caliper PS-matching can yield highly variable estimates of the treatment-outcome association if the analysis is repeated.

Effect of fund support on cited times of Chinese papers on AIDS / 中华医学图书情报杂志

Objective To study the effect of fund support on cited times of Chinese papers on AIDS by controlling the influence of confounding factors.Methods The effect of publication time of fund-supported papers and non fund-supported papers, h-index of authors, IF of journals on accumulated cited times of each academic paper was controlled by propensity score matching.The cited times of matched fund-supported papers and non fund-supported papers were compared by paired t test.Results The balance of confounding factors which were unbalanced before matching was achieved between fund-supported papers and non fund-supported papers after matching.No significant difference was found between fund-supported papers and non fund-supported papers after matching.Conclusion Fund support does not affect the cited times of Chinese papers on AIDS, which shows that fund support can not noticeably improve the academic level and impact of Chinese papers on AIDS.

Mahalanobis' distance and propensity score to construct a controlled matched group in a Brazilian study of health promotion and social determinants / Distância de Mahalanobis e escore de propensão para seleção de amostra pareada de controle em um estudo Brasileiro de promoção da saúde e determinantes sociais

In observational epidemiology it is usual to select a control group to study the effects of certain exposures on human health. Intervention studies are well known among epidemiologists but it is not very frequent in other areas of research. In this paper we propose the same idea of intervention studies and the use of three methods for a health promotion research control group selection: Propensity score, Mahalanobis' distance and Mahalanobis within Propensity Calipers. In the original project, "Health and Local Development: a progress review towards the millennium goals with relation to health in the Brazilian cities which develop social agendas", cities with social agendas from Brazil were matched separately by state. In the state of Paraná there are 397 cities. Of these, 34 presented social agendas implemented and active since, at least, 2004. Five variables measured in 2000 were considered for the matching: population size, human development index of income, human development index of education, percentage of literacy and vaccine coverage. As a result, among these three methods, the Mahalanobis by itself was considered the less efficient. In conclusion, the propensity, which is a very simple linear score, presented very good matched sample. However, the Mahalanobis within Calipers was the method that provided the best result.

Em epidemiologia observacional, é frequente o uso de grupos controle para avaliação do efeito de variáveis de exposição em desfechos na saúde de pessoas, porém este método não é muito utilizado em outras áreas. Este artigo propõe a aplicação da ideia de estudos de intervenção, com base em seleção de grupo controle, utilizando três métodos de seleção de amostra (escore de propensão, distância de Mahalanobis e distância de Mahalanobis dentro da margem estabelecida pelo escore de propensão) para pesquisa de promoção da saúde. No projeto “Saúde e desenvolvimento local: análise dos progressos em relação aos objetivos de desenvolvimento do milênio relacionados à saúde, nas cidades brasileiras que desenvolvem agendas sociais”, cidades com agendas sociais foram pareadas com amostra controle sem agendas sociais, para cada um dos estados do Brasil. Neste artigo foi considerado o estado do Paraná que tem 397 cidades sendo 34 com agendas sociais implementadas desde pelo menos 2004. Cinco variáveis, coletadas em 2000, foram consideradas para o pareamento: tamanho populacional, índice de desenvolvimento humano econômico e educacional, percentual de pessoas escolarizadas e cobertura vacinal. O resultado do pareamento com o uso da distância de Mahalanobis foi o que apresentou menor qualidade. Conclui-se que o método do escore de propensão, o mais simples e mais facilmente utilizado, apresentou como resultado um grupo de controle confiável. Entretanto, a distância de Mahalanobis dentro de margens do escore de propensão é o método que obteve o melhor resultado.