An overview of the objectives of and the approaches to propensity score analyses

The assessment of treatment effects from observational studies may be biased with patients not randomly allocated to the experimental or control group. One way to overcome this conceptual shortcoming in the design of such studies is the use of propensity scores to adjust for differences of the characteristics between patients treated with experimental and control interventions. The propensity score is defined as the probability that a patient received the experimental intervention conditional on pre-treatment characteristics at baseline. Here, we review how propensity scores are estimated and how they can help in adjusting the treatment effect for baseline imbalances. We further discuss how to evaluate adequate overlap of baseline characteristics between patient groups, provide guidelines for variable selection and model building in modelling the propensity score, and review different methods of propensity score adjustments. We conclude that propensity analyses may help in evaluating the comparability of patients in observational studies, and may account for more potential confounding factors than conventional covariate adjustment approaches. However, bias due to unmeasured confounding cannot be corrected fo

Herz-Kreislauf-Krankheiten

Rund ein Drittel der weltweiten Todesfälle sind auf Herz-Kreislauf-Krankheiten zurückzuführen. In den industrialisierten Ländern sind sie die häufigste Todesursache. Den größten Anteil hat dabei die koronare Herzkrankheit, gefolgt vom Schlaganfall und der Herzinsuffizienz. In westlichen Industrienationen dürfte jede zweite Person im Lauf ihres Lebens an Herz-Kreislauf-Krankheiten erkranken. Da das Risiko mit zunehmendem Alter zunimmt, wird die Anzahl von Herz-Kreislauf- Erkrankungen aufgrund der demografischen Entwicklung in Zukunft weiter ansteigen. In diesem Abschnitt betrachten wir zuerst die epidemiologische Bedeutung der Herz-Kreislauf-Krankheiten und schauen hier insbesondere auf die globale Bedeutung, die geografischen Unterschiede sowie die sich derzeit entwickelnden zeitlichen Trends. Anschließend erörtern wir, welche Risikofaktoren zur Entstehung von Herz-Kreislauf-Krankheiten beitragen und mit welchen präventiven Maßnahmen diese Erkrankungen zu verhindern sind. Schweizerische Lernziele: CPH 34–35, CPH 37, CPH 40–4

The role of correspondence sections in post-publication peer review: A bibliometric study of general and internal medicine journals

Scientific journals claim that correspondence sections are for post-publication peer review. We compared the conditions for submission and the bibliometrics of letters-to-editors published in leading medical journals in 2002 and 2007 using journal-derived information and data from PubMed and Journal Citation Reports. The median time limit for letter submissions decreased from 6 to 3.5 weeks, the median word limit from 400 to 350. The median number of letters per published article was near one in both years. Only about half of the letters were followed by an author reply in either year. Electronic response systems were available for four journals in 200

An overview of the objectives of and the approaches to propensity score analyses

The assessment of treatment effects from observational studies may be biased with patients not randomly allocated to the experimental or control group. One way to overcome this conceptual shortcoming in the design of such studies is the use of propensity scores to adjust for differences of the characteristics between patients treated with experimental and control interventions. The propensity score is defined as the probability that a patient received the experimental intervention conditional on pre-treatment characteristics at baseline. Here, we review how propensity scores are estimated and how they can help in adjusting the treatment effect for baseline imbalances. We further discuss how to evaluate adequate overlap of baseline characteristics between patient groups, provide guidelines for variable selection and model building in modelling the propensity score, and review different methods of propensity score adjustments. We conclude that propensity analyses may help in evaluating the comparability of patients in observational studies, and may account for more potential confounding factors than conventional covariate adjustment approaches. However, bias due to unmeasured confounding cannot be corrected for

Placebo-controlled trials of Chinese herbal medicine and conventional medicine—comparative study

Background Chinese herbal medicine (CHM) is increasingly used in the West, but the evidence on its effectiveness is a matter of debate. We compared the characteristics, study quality and results of clinical trials of CHM and conventional medicine. Methods Comparative study of placebo-controlled trials of CHM and conventional medicine. Eleven bibliographic databases and searches by hand of 48 Chinese-language journals. Conventional medicine trials matched for condition and type of outcome were randomly selected from the Cochrane Controlled Trials Register (issue 1, 2003). Trials described as double-blind, with adequate generation of allocation sequence and adequate concealment of allocation, were assumed to be of high quality. Data were analysed using funnel plots and multivariable meta-regression models. Results 136 CHM trials (119 published in Chinese, 17 published in English) and 136 matched conventional medicine trials (125 published in English) were analysed. The quality of Chinese-language CHM trials tended to be lower than that of English-language CHM trials and conventional medicine trials. Three (2%) CHM trials and 10 (7%) conventional medicine trials were of high quality. In all groups, smaller trials showed more beneficial treatment effects than larger trials. CHM trials published in Chinese showed considerably larger effects than CHM trials published in English (adjusted ratio of ORs 0.29, 95% confidence intervals 0.17-0.52). Conclusions Biases are present both in placebo-controlled trials of CHM and conventional medicine, but may be most pronounced in CHM trials published in Chinese-language journals. Only few CHM trials of adequate methodology exist and the effectiveness of CHM therefore remains poorly documente

Blood glucose, diabetes and metabolic control in patients with community-acquired pneumonia

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