TABLE 15 Characteristics of a Well Designed Systematic Review

Are the results valid? Did the review address a focused clinical question? Were the criteria for study selection appropriate? Was the validity of individual studies assessed? Was study selection and review performed independently and was it reproducible? What are the results? What are the overall results of the study? How precise were the results? Can the results be applied to patient care? Can the results be applied to my patient population? Were all clinically relevant outcomes addressed? Are the benefits worth the potential harms and costs?

and a specificity of 82% for identifying a polyp. The PPV is 84% and the NPV is 82%. The likelihood ratio for a positive test is 5, and the likelihood ratio of a negative test is 0.2. The prevalence of polyps in this high risk group of patients was 51%. Using this prevalence and these likelihood ratios, a positive CT colonography implies that a patient with a 51% pretest probability has a posttest probability of having polyps in the colon of 81%. A negative CT colonography implies a 17% posttest probability of having polyps in the colon (Stronger data using three-dimensional [3-D] CT is presented in Pickhardt et al, 2003).

The final step in this exercise is applying the results of the study to your scenario. Although this study fulfills the validity criteria for a study about diagnosis and the results are likely accurate, there are some potential limitations. The investigators chose a narrowly defined patient population that had a higher pretest probability of advanced polyps

than the "spectrum" of asymptomatic patients over 50 years of age who will be screened for colorectal polyps and cancer. Additionally, this study did not report the interobserver variation associated with CT colonography and other studies that have reported less promising results for the detection of smaller polyps. Thus, because evidence did not support using CT colonography in an average risk screening population, and the data may not be as strong for the detection of small or flat lesions, you advised against initiation of the program until such time as there was evidence to support CT colonography for average risk colorectal cancer screening. There is a separate chapter on colorectal cancer screening (see Chapter 93, "Colorectal Polyp and Cancer Screening") which refers to the more accurate 3-D CT data (Pickhardt et al, 2003).

Constipation Prescription

Constipation Prescription

Did you ever think feeling angry and irritable could be a symptom of constipation? A horrible fullness and pressing sharp pains against the bladders can’t help but affect your mood. Sometimes you just want everyone to leave you alone and sleep to escape the pain. It is virtually impossible to be constipated and keep a sunny disposition. Follow the steps in this guide to alleviate constipation and lead a happier healthy life.

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