Update in Gastroenterology and Hepatology

We have several goals for this update, the most important one being to review the pertinent literature in gastroenterology and hepatology that appeared in 2004. Some of these papers contain important resource utilization implications that need debate. Others will provide opportunities to consider topics about critical reading of the literature.

Several of the papers included in this update are systematic reviews. Systematic reviews differ from the usual review articles we read, known as narrative reviews. The systematic review is analogous to a research project. Before anything is written, a protocol is created. A very specific question is posed, and the authors decide how they are going to use the literature to find the answer to that question. The conclusion must be driven by the data, consequently avoiding many of the biases that sneak into the narrative review.

Some systematic reviews combine data from randomized, controlled trials (RCTs) using a process called meta-analysis. The advantages of meta-analysis are increased power to see a difference and a more precise definition of the magnitude of any effect that is present. The downside of combining data from different studies is that studies often differ in ways that influence the results, a problem called heterogeneity. One must keep this in mind when reading any meta-analysis; no 2 studies are created exactly the same.

The result of a meta-analysis (“estimated effect”) can be presented in several ways. The absolute risk difference (ARD) is the easiest to understand. The ARD represents the difference between the frequency of the event in the treated group and the frequency of the event in the control group.

The relativerisk (RR) is another way to present the estimated effect; it is the ratio between the rate of the outcome …