<< An Evidence-Based Approach To Emergency Ultrasound

Critical Appraisal Of The Literature

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Critical Appraisal Of The Literature

Critical Appraisal Of The Literature

For some applications of EUS, the existing literature is vast; for others, it is limited. In the more established applications, research has moved beyond the assessment of technical and diagnostic accuracy toward diagnostic decision-making and patient outcomes research. A few general statements can be made regarding much of the research on EUS. First, ultrasound is operator-dependent. Results are conditional and based on the sonographer’s skill level, making generalizability a concern. Second, EUS is a diagnostic and resuscitative imaging modality, and its impact on patient outcomes is more challenging to study than that of other interventions. Third, many ultrasound studies are convenience samples, since emergency medicine providers who are sufficiently trained in sonography are not always available to enroll patients in a consecutive manner. Fourth, chart reviews with EUS — like all chart reviews — depend on the availability and accuracy of bedside ultrasound data, and the quality of these data is highly variable.

The 2008 ACEP Emergency Ultrasound Guidelines effectively summarizes the quality of clinical ultrasound research by defining classes of evidence1:

  • Class I Evidence: Randomized controlled trials (RCTs) are the gold standard
  • Class II Evidence:
  • A. Data collected prospectively
  • B. Retrospective analyses from clearly reliable data
  • Class III Evidence: Most studies based on retrospectively collected data

Based on this system of ranking, some Class I evidence exists for ultrasound-assisted central venous cannulation and the FAST examination, but most publications offer Class II (both A and B) evidence. Published literature for clinical sonographic evaluation of other established applications, including abdominal aortic aneurysm, cardiac tamponade and global inotropy, early intrauterine pregnancy confirmation, and shock states, represent Class II (both A and B) and Class III evidence. Some Class II data exist for the newer applications of EUS, but the majority of the literature remains Class III evidence.

In general, the EUS literature continues to grow and the quality of the studies continues to improve. As data collection becomes standardized and as more widespread data networks are established, larger multicenter studies are on the horizon.

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