2001年英国Cochrane中心联合循证医学和临床流行病学领域最权威的专家,根据研究类型分别制定了详细的分级并沿用至今。这个版本将证据仍分5级,但对每个级别进行了细化。 推荐强度分A~D四级 A 结果一致的Ⅰ级临床研究结论; B 结果一致的Ⅱ、Ⅲ级临床研究结论或Ⅰ级临床研究的推论; C Ⅳ级临床研究的结论或Ⅱ、Ⅲ级临床研究的推论; D Ⅴ级临床研究的结论或任何级别多个研究有矛盾或不确定的结论。 CTFPHC证据分级(1999) Ⅰ 大样本双盲RCT或中样本RCT的Meta分析得出的与临床相关的结果 Ⅱ 小样本RCT;未使用盲法的RCT,采用有效替代标志物(surrogate markers)的RCT Ⅲ 非随机对照研究,观察性(队列)研究,病例对照研究或横断面研究 Ⅳ 专家委员会或相关权威的意见 Ⅴ 专家意见 UK Cochrane中心证据分级(2001) 1a 同质RCT的系统评价 1b 单个RCT (可信区间窄) 1c 全或无病案系列 2a 同质队列研究的系统评价 2b 单个队列研究 (包括低质量RCT,如随访率<80%) 2c 结果研究,生态学研究 3a 同质病例对照研究的系统评价 3b 单个病例对照 4 病例系列研究(包括低质量队列和病例对照研究) 5 基于经验未经严格论证的专家意见 牛津循证医学中心 Ia Evidence from meta-analysis of randomised controlled trials Ib Evidence from at least one randomised controlled trial IIa Evidence from at least one controlled study without randomisation IIb Evidence from at least one other type of quasi-experimental study III Evidence from non-experimental descriptive studies comparative, correlation, and case-control IV Evidence from reputable sources expert committee reports, opinions, clinical experience, respected authorities 其他分级标准 I Well-designed randomised controlled trials II-1 Other types of trials ( Well-designed controlled trials without randomisation) II-2 Well-designed cohort (prospective) study, preferably from more than one centre II-3 Well-designed case-control (retrospective) study, preferably from several centres III Large differences from comparisons between times and/or places with or without the intervention IV Opinions of respected authorities based on clinical experience; descriptive studies and reports of expert committees