Clinical infectious diseases : an official publication of the Infectious Diseases Society of America
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Appropriate end points are crucial for the successful interpretation of clinical trials. Choosing end points for therapeutic trials of ventilator-associated pneumonia (VAP) and hospital-acquired pneumonia (HAP) requires careful consideration, because they are complications of critical illness. It may be difficult to distinguish the consequences of VAP and HAP from manifestations of the underlying illnesses, and it is important to determine their incremental magnitude, to plan for possible treatment effects and, thus, sample size calculations. ⋯ Because of these findings, superiority trials of VAP treatment that use mortality as a primary end point are not possible. Equivalency studies are possible, but there are sample size implications. The use of time to clinical event end points, especially when combined with mortality, may be the best option for trial in the future.
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For treatment studies of an infectious disease, such as pneumonia, microbiologic eradication is the logical primary end point. Several problems for pneumonia in general and several more specific to VAP preclude the use of microbiologic eradication as a primary end point. These problems include no positive culture result at baseline, difficulty distinguishing colonization from infection on baseline cultures, no specimen available for testing when determining cure, and induction of colonization by antibiotic treatment. ⋯ Although promising, especially for open-label studies focused on multidrug-resistant pathogens, further research is needed before serial quantitative cultures can be used to define microbiologic failure. Of the biomarkers, procalcitonin level may be a valuable adjunct to clinical evaluation but cannot be a primary end point alone. A decreasing or low procalcitonin level after initiation of antibiotic treatment correlates well with bacterial eradication.
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There is an increasing focus on having quality systems in place during the planning stages of clinical trials. Such systems require the development and implementation of standards for each step. Although this is not imposing something totally new on clinical research, a systematic approach will produce a more reliable and useful end product--high-quality data obtained without compromising the protection of human subjects' rights and welfare. A suggested quality system with standards for each step is addressed in this article.