不同研究方法在循证医学证据体系中的价值辨析

The values of different study designs on the levels of evidence： a descriptive analysis of the researches published in four general medical journals in 2009

目的 以《新英格兰医学杂志》、《美国医学会杂志》、《柳叶刀》和《英国医学杂志》2009年发表的＂论著＂型文章为例,讨论不同的研究方法在循证医学证据体系中的价值.方法 通过上述杂志的官方网站逐期检索其刊载的论著及系统综述和Meta分析.用Epidata 3.1软件建立信息摘录表,摘录＂文献题目＂、＂第一作者所在国家＂、＂临床问题＂及＂研究类型＂等内容.用SPSS13.0软件进行描述性分析.结果 共纳入844篇论著,其中RCT占35.7%,系统综述和Meta分析占9.4%,其他研究54.9%.在临床问题方面,探讨＂治疗＂（34.2%）、＂病因或危险因素＂（19.7%）、＂预防＂（13.7%）、＂疾病频率＂（6.0%）和＂预后＂（5.1%）的文献较多,与之对应的最常见研究类型分别为RCT（70.6%）、队列研究（44.6%）、RCT（68.1%）、横断面研究（56.9%）和队列研究（93.0%）.结论 高水平的临床证据不限于RCT和系统综述,各种研究方法均有其独特的价值.研究者应根据所针对的临床问题或研究阶段等具体情况的不同来选择最适宜的研究设计类型.

Objective To discuss the levels of evidence provided by different study designs.Methods Websites of N Engl J Med, JAMA, Lancet, and BMJ were accessed to identify research articles （systematic review and meta-analysis included） published in 2009. A standardized data collection form was established using Epidata 3. 1 software to extract the ＂title＂, ＂country of lead author＂, ＂clinical problem＂ （such as treatment, diagnosis, etc. ） and ＂study design＂ of eligible studies. Descriptive statistics was conducted with SPSS 13.0. Results Over all, 844 studies were included, among which 35.7% were RCT,9. 4% systematic review and Meta-analysis, and 54. 9% other types of studies. Regarding clinical problems,34. 2%, 19. 7%, 13.7%, 6. 0% and 5. 1% of the included researches addressed the issues of treatment,etiology/risk factors, prevention, disease frequency and prognosis, respectively. The study designs that were most frequently adopted to explore these problems were RCT （70.6%）, cohort study （44. 6% ）, RCT （68. 1% ）, cross-sectional study （ 56. 9% ）, and cohort study （ 93.0% ）, respectively. Conclusions High-level evidence does not come exclusively from RCT and systematic review, as each type of study may have its unique value in health related research. The clinical problem of interest, the previous work that has been done to approach the same issue, as well as other factors should be taken into account when deciding whether the selected study design is appropriate.