A mean of systematic review of diagnostic tests based on The Bayes Library of Diagnostic Studies and Reviews (2nd edition 2002) and Bayes Library are introduced to Chinese readers who are interesting on diagnostic test and screening systematic review.
In this paper, we introduce theory and practice method about combining independent studies of Diagnostic test into a summary ROC curve. This is a useful and easily applied by clinicians to analyse the data of diagnostic test. It’s referance for user and doer of EBM in China.
Liver fibrosis in chronic liver disease refers to the body’s repair response to sustained repeated necrosis or inflammation of liver cells, which results in fibrosis accompanied by relative or absolute lack of fiber degradation and deposition of extracellular matrix in the liver. Early and timely diagnosis and treatment of hepatic fibrosis are of great importance to patients with liver disease. A rational and complete diagnostic model of liver fibrosis should involve clinical pathology and histology, imaging, and serum biochemical markers. Liver biopsy has been regarded as the "gold standard" for the diagnosis of liver fibrosis and as a reference standard for other non-invasive diagnostic tests of liver fibrosis. Since it is invasive, liver biopsy is difficult to implement in clinical practice and a second liver biopsy is even more difficult. As for the non-invasive diagnosis of liver fibrosis, clinical symptoms and signs are not specific. The sensitivity and specificity of individual serum biochemical markers are still very weak, and imaging studies also lack specificity. The mathematical model “FibroTest” of serum biochemical markers has better diagnostic accuracy, but the calculation is complicated, making it difficult to achieve widespread use. There is insufficient evidence to suggest that the "gold standard" of liver biopsy can be replaced. Therefore, further research is needed to investigate how best to balance the benefits and harms of different tests, to identify the best combination, to simplify any calculation steps, to reduce costs, to avoid liver biopsy, and to find new, more specific and sensitive markers.
We described our understanding of EBM, the ‘three principles＇ and ‘five steps＇ to practice it. EBM is an embodiment of human moral rule and axiom in clinical medicine; it is an advanced clinical model and medical practical methodology; it results from a basis of developed and perfected clinical research methodology, best evidence database, information technology. We also discussed the relationship between EBM and traditional Chinese medicine （TCM） modernization. The definition of modernization of TCM was suggested as scientifical standardization and internationalization. TCM theory in fact is not a basic but a clinical practice theory. EBM model should become the standard model of TCM practice to accelarate the standardization of TCM diagnostic technique and therapy. The key is not try to explain TCM theories with modern medical theroies, but work out common effectiveness evaluation criteria. Only when the effectiveness is intemationally acknowledged, can TCM be internationalized.
Some statistical measures in evidence-based medicine, such as RRR, ARR and NNTwere introduced.
In this paper , the statistic significance and clinical application of forest plots in a meta-analysis have been fully discussed. If the horizontal line represents the 95% confidence interval of the indexes including odds ratio, relative risk, weighted mean difference, and standard mean difference crosses the vertical line, the effect of test group is not signficant with that of control group; if the horizontal line lies to the right of the vertical line, it indicates that the test group is significantly effctive. If the horizontal line lies to the left of the vertical line, it indicates that the control group is more effective. In addition, it doesn’t mean that clinical application is more beneficial, if the treatment study has more effect, because experimental factor can be positive or negative.
In this paper, we introduce meaning and purpose of confidence interval (CI) in evidence-based medicine, For example, RRR ,ARR ,NNT. It s referance for user and doer of EBM in China.
NNT defines the number of patients who need to be treated in order to achieve one additional favorable outcome, and NNH is defined as the number of patients who must be treated with a therapy in order to have one additional patient suffer an adverse effect compared with the control treatment. This is the most important thing that should beconsidered before administering a treatment. NNT can also be used to assess the relative benefit or harm in the comparison of intervention versus positive control. If the effect is smaller in the intervention group than that in the control group, NNT should be used; if the effect is bigger in the intervention group than that in the control group, NNH should be used. When comparison is made between an intervention versus placebo, NNT and NNH are absolute outcomes; when an intervention is compared to a positive control, NNT and NNH are relative outcomes. RR or OR or RD may help to judge which comparator has bigger or smaller effect, and whether NNT or NNH should be used.
The necessity and methods of systematic review or Meta-analysis of observational studies were introduced. The difference between the systematic review or Meta-analysis of observational studies and randomized controlled trials was also described.
Objective To formulate an evidence-based conclusion concerning ultrasound screening for fetal malformations for a pregnant woman after 12 gestational weeks. Methods Based on the clinical problem of whether pregnant women need ultrasound screening for fetal malformations after 11-14 gestational weeks, we used “ultrasound or sonography and prenatal or fetal at first trimester or 11-14 weeks; ultrasound exposure; fetal development” as the keywords and searched The Cochrane Library (Issue 4, 2008), MEDLINE (1981 to 2008), ACP Journal Club (1991 to 2008), and BMJ Clinical Evidence (1999 to 2008) for systematic reviews, randomized controlled trials (RCTs) and controlled clinical trials. The methodological quality of the included studies was assessed to identify the current best evidence. Results Three systematic reviews, two RCTs and ten cohort studies were retrieved. The results showed ultrasound screening detected different fetal malformations in the first, second and third trimester. Not all of the fetal malformations could be detected through prenatal ultrasound screening. Nuchal translucency (NT) measurement as a tool for screening chromosomally abnormal fetuses and detecting fetal malformations by ultrasound proved to be effective if performed within 11-14 gestational weeks. The routine second trimester screening, however, could not be replaced by a detailed ultrasound examination at 11-14 gestational weeks. Most of the trials concluded that the effect of ultrasound on a fetus was not harmful. Conclusion The findings of this study should reassure physicians and parents alike that ultrasound screening is an appropriate option for the pregnant women after 12 gestational weeks.