Bmc Med Res Methodol
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Bmc Med Res Methodol · Jan 2005
Randomized Controlled TrialA randomised controlled trial to assess the effectiveness of offering study results as an incentive to increase response rates to postal questionnaires [ISRCTN26118436].
Postal questionnaires are widely used to collect outcome data on participants. However, a poor response to questionnaires will reduce the statistical power of the study and may introduce bias. A meta analysis of ten trials offering study results, largely in the fields of education and marketing, was shown to be ineffective, with the odds ratio for response with offering research findings is 0.92 (95% CI 0.75 to 1.11). However uncertainty still exists as it is uncertain whether results from such trials can be extrapolated to that of a health care setting. The aim of this study was to assess whether offering participants study results increases the response rates to postal questionnaires. ⋯ Offering study results to women living in the community aged over 70 does not increase response rates to postal questionnaires. Although researchers have an ethical obligation to offer participants study results, since 10% of women did not wish to receive the results, investigators should give participants the option to opt out of receiving the study's results.
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Bmc Med Res Methodol · Jan 2005
Comparative StudyLack of interchangeability between visual analogue and verbal rating pain scales: a cross sectional description of pain etiology groups.
Rating scales like the visual analogue scale, VAS, and the verbal rating scale, VRS, are often used for pain assessments both in clinical work and in research, despite the lack of a gold standard. Interchangeability of recorded pain intensity captured in the two scales has been discussed earlier, but not in conjunction with taking the influence of pain etiology into consideration. ⋯ The pain intensity assessments on VAS and VRS are in this study, not interchangeable due to overlap of pain records between the two scales, systematic disagreements when comparing the two scales and a low percentage intra-scale agreement. Furthermore, the lower VAS cut-off positions relative the VRS labels indicate different meaning of the rated pain intensity depending on pain etiology. It is also indicated that the scales have non-linear properties and that the two scales probably have different interpretation. Our findings are in favor of using the VRS in pain intensity assessments but if still the VAS is preferred, the VAS data should be analyzed as continuous using statistical methods suitable for ordinal data. Furthermore, our findings indicate a risk to over or under estimate the patient's perceived pain when interpreting condensed VAS data.
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Bmc Med Res Methodol · Jan 2005
Comparative StudyAdaptive designs based on the truncated product method.
Adaptive designs are becoming increasingly important in clinical research. One approach subdivides the study into several (two or more) stages and combines the p-values of the different stages using Fisher's combination test. ⋯ It is recommended to apply the TPM rather than Fisher's combination test whenever an early termination due to insufficient effects is not suitable within the adaptive design.
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Bmc Med Res Methodol · Jun 2004
The Platino project: methodology of a multicenter prevalence survey of chronic obstructive pulmonary disease in major Latin American cities.
The prevalence of Chronic Obstructive Pulmonary Disease (COPD) in many developed countries appears to be increasing. There is some evidence from Latin America that COPD is a growing cause of death, but information on prevalence is scant. It is possible that, due to the high frequency of smoking in these countries, this disease may represent a major public health problem that has not yet been recognized as such. The PLATINO study is aimed at measuring COPD prevalence in major cities in Latin America. ⋯ The PLATINO project will provide a detailed picture of the global distribution of COPD in Latin America. This project shows that studies from Latin America can be carried out with adequate quality and be of scientific value.
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Bmc Med Res Methodol · May 2004
Comparative StudyThe level of non-citation of articles within a journal as a measure of quality: a comparison to the impact factor.
Current methods of measuring the quality of journals assume that citations of articles within journals are normally distributed. Furthermore using journal impact factors to measure the quality of individual articles is flawed if citations are not uniformly spread between articles. The aim of this study was to assess the distribution of citations to articles and use the level of non-citation of articles within a journal as a measure of quality. This ranking method is compared with the impact factor, as calculated by ISI(R). ⋯ Ranking journals by impact factor and non-citation produces similar results. Using a non-citation rate is advantageous as it creates a clear distinction between how citation analysis is used to determine the quality of a journal (low level of non-citation) and an individual article (citation counting). Non-citation levels should therefore be made available for all journals.