Baseline Assessment
In clinical trials, baseline refers to the status of a participant before the start of intervention. Baseline data may be measured by interview, questionnaire, physical examination, laboratory tests, and procedures. Measurement need not be only numerical
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Baseline Assessment
In clinical trials, baseline refers to the status of a participant before the start of intervention. Baseline data may be measured by interview, questionnaire, physical examination, laboratory tests, and procedures. Measurement need not be only numerical in nature. It can also mean classification of study participants into categories based on factors such as absence or presence of some trait or condition. There are multiple uses of the baseline data. First, there is a need to describe the trial participants so the readers of the trial publications can determine to which patient population the findings apply. Second, it is important methodologically to present relevant baseline data by study group in order to allow assessment of group comparability and answer the question whether randomization generated balanced groups. Third, baseline data are used in statistical analyses to control for any baseline imbalances. Finally, baseline data form the basis for subgroup analyses of the trial findings. This chapter is concerned with these uses of the baseline data.
Fundamental Point Relevant baseline data should be measured in all study participants before the start of intervention.
Uses of Baseline Data Description of Trial Participants Because the trial findings in a strict sense only apply to the participants enrolled in the trial, it is essential that they are properly and as completely as possible © Springer International Publishing Switzerland 2015 L.M. Friedman et al., Fundamentals of Clinical Trials, DOI 10.1007/978-3-319-18539-2_9
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9 Baseline Assessment
described. This is done in the typical Table 1 of the results publication. The description of baseline covariates provides documentation that can guide cautious extrapolation of trial findings to other populations with the same medical condition [1]. A common limitation is that the characteristics of the excluded participants with the study condition are seldom reported. To the reader, it would also be helpful to know what proportion of the study population was excluded. In other words, what was the recruitment yield? Also of interest would be a presentation of the reasons for exclusion. Based on the published information, clinicians need to know to which of their patients the findings directly apply. They also need to know the characteristics of the excluded patients with the study condition, so they can determine whether the trial findings can reasonably be extrapolated. The amount of data collected at baseline depends on the nature of the trial and the purpose for which the data will be used. As mentioned elsewhere, some trials have simple protocols which means that detailed documentation of many baseline variables is omitted and only a few key demographic and medical variables are ascertained. If such trials are large, it is reasonable to expect that good balance between groups will be achieved. Because the goals of these trials are restricted to answering the primary question and one or two secondary questions, the other uses f
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